Note: Descriptions are shown in the official language in which they were submitted.
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SURFACE GRAVITY WAVE GENERATOR AND WAVE POOL
[0001]
BACKGROUND
[0002] Ocean waves have been used recreationally for hundreds of years. One
of the
most popular sports at any beach with well-formed, breaking waves is surfing.
Surfing and
other board sports have become so popular, in fact, that the water near any
surf break that is
suitable for surfing is usually crowded and overburdened with surfers, such
that each surfer
has to compete for each wave and exposure to activity is limited. Further, the
majority of the
planet's population does not have suitable access to ocean waves in order to
even enjoy
surfing or other ocean wave sports.
[0003] Another problem is that the waves at any spot are varied and
inconsistent, with
occasional "sets" of nicely formed waves that are sought after to be ridden,
interspersed with
less desirable and, in some cases, unrideable waves. Even when a surfer
manages to be able to
ride a selected wave, the duration of the ride lasts only a mere 2-30 seconds
on average, with
most rides being between 5 and 10 seconds long.
[0004] Ocean surface waves are waves that propagate along the interface
between
water and air, the restoring force is provided by gravity, and so they are
often referred to as
surface gravity waves. FIG. 1 illustrates the principles that govern surface
gravity waves
entering shallow water. Waves in deep water generally have a constant wave
length. As the
wave interacts with the bottom, it starts to "shoal." Typically, this occurs
when the depth gets
shallower than half of the wave's length, the wave length shortens and the
wave amplitude
increases. As the wave amplitude increases, the wave may become unstable as
the crest of the
wave is moving faster than the trough. When the amplitude is approximately 80%
of the water
depth the wave starts to "break" and we get surf. This run up and breaking
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process is dependent on the slope angle and contour of the beach, the angle at
which the
waves approach the beach, and the water depth and properties of the deep water
waves
approaching the beach. Refraction and focusing of these waves is possible
through changes to
the bottom topography.
[0005] Ocean waves generally have five stages: generation, propagation,
shoaling,
breaking, and decay. The shoaling and breaking stages are the most desirable
for rideable
waves. The point of breaking being strongly dependent on the ratio of the
water depth to the
wave's amplitude but also depends on the contour, depth and shape of the ocean
floor. In
addition, velocity, wavelength and height of the wave, among other factors,
can also
contribute to the breaking of a wave. In general, a wave can be characterized
to result in one
of four principal breaker types: spilling, plunging, collapsing, and surging.
Of these wave
types the spilling waves are preferred by beginner surfers while the plunging
waves are
revered by more experienced surfers. These breaker types are illustrated in
FIG. 2.
[0006] Various systems and techniques have been tried to replicate ocean
waves in a
man-made environment. Some of these systems include directing a fast moving,
relatively
shallow sheet of water against a solid sculpted waveform to produce a water
effect that is
ridable but is not actually a wave. Other systems use linearly-actuated
paddles, hydraulics or
pneumatics caissons or simply large unlimited injections of water to generate
actual waves.
However, all of these systems are inefficient in transferring energy to the
"wave", and none
of these systems, for various reasons and shortcomings, have yet to come close
to generating
a wave that replicates the desired size, form, speed and break of the most
desirable waves that
are sought to be ridden, i.e. waves entering shallow water that plunge,
breaking with a tube
and which have a relatively long duration and sufficient face for the surfer
to maneuver.
SUMMARY
[0007] This document presents a wave generator system and wave pool that
generates
surface gravity waves that can be ridden by a user on a surfboard.
[0008] The wave pool includes a pool for containing water and defining a
channel
having a first side wall, a second side wall, and a bottom with a contour that
slopes upward
from a deep area proximate the first side wall toward a sill defined by the
second side wall.
The wave pool further includes at least one foil at least partially submerged
in the water near
the side wall, and being adapted for movement by a moving mechanism in a
direction along
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the side wall for generating at least one wave in the channel that forms a
breaking wave on the
sill; and
[0009] In aspect, the wave pool includes one or more passive flow control
mechanisms to mitigate a mean flow of the water induced by the movement of the
at least one
foil in the direction along the side wall. In another aspect, the wave pool
includes one or more
passive current control gutter mechanisms to mitigate currents in the water
induced by the
movement of the at least one foil in the direction along the side wall. In yet
another aspect, the
wave pool includes a passive chop and seich control mechanism to mitigate
random chop and
seich in the water at least partially induced by the movement of the at least
one foil in the
direction along the side wall, and at least partially induced by a shape and
the contour of the
channel. In still yet another aspect, the wave pool can include any or all of
the aforementioned
control mechanisms for controlling and/or minimizing water flow, chop or
auxiliary waves
besides a main surface gravity wave generated by each of the at least one
foil.
[0009a] According to one aspect of the present invention, there is
provided a wave pool
comprising: a pool for containing water, the pool defining a channel having: a
first side, the
first side being any of an island; a shoal; a beach; and a wall; a second
side, the second side
being any of a shoal; a beach; and a wall; and a bottom with a contour that
slopes upward
from a deep area proximate the first side toward a sill defined by the second
side; and at least
one foil at least partially submerged in the water near the first or second
side, and being
adapted for movement by a moving mechanism in a direction along the side for
generating at
least one wave in the channel that forms a breaking wave on the sill; and one
or more passive
current control gutter mechanisms to mitigate currents in the water induced by
the movement
of the at least one foil in the direction along the side.
10009b1 According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a first side
wall, a second side wall, and a bottom with a contour that slopes upward from
a deep area
proximate the first side wall toward a sill defined by the second side wall;
at least one foil at
least partially submerged in the water near at least one of the first side
wall and the second
side wall, and being adapted for movement by a moving mechanism in a direction
along the
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side wall for generating at least one wave in the channel that forms a
breaking wave on the
sill; and one or more passive flow control mechanisms to mitigate a mean flow
of the water
induced by the movement of the at least one foil in the direction along the
side wall, the one
or more passive flow control mechanisms including a plurality of vortex
generators provided
and spaced apart on a surface of the channel and under a surface of the water.
[0009c] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a first side
wall, a second side wall, and a bottom with a contour that slopes upward from
a deep area
proximate the first side wall toward a sill defined by the second side wall;
at least one foil at
least partially submerged in the water near at least one of the first side
wall and the second
side wall, and being adapted for movement by a moving mechanism in a direction
along the
side wall for generating at least one wave in the channel that forms a
breaking wave on the
sill; and one or more passive current control gutter mechanisms to mitigate
currents in the
water induced by the movement of the at least one foil in the direction along
the side wall.
[0009d] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a first side
wall, a second side wall, and a bottom with a contour that slopes upward from
a deep area
proximate the first side wall toward a sill defined by the second side wall;
at least one foil at
least partially submerged in the water near at least one of the first side
wall and the second
side wall, and being adapted for movement by a moving mechanism in a direction
along the
side wall for generating at least one wave in the channel that forms a
breaking wave on the
sill; and a passive chop and seich control mechanism to mitigate random chop
and seich in the
water at least partially induced by the movement of the at least one foil in
the direction along
the side wall, and at least partially induced by a shape and the contour of
the channel, the
passive chop and seich control mechanism including a gutter system on the side
wall of the
channel, the gutter system comprising one or more perforated walls to form a
cavity between
the side wall of the channel and a path of the at least one foil.
[0009e] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a first side
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wall, a second side wall, and a bottom with a contour that slopes upward from
a deep area
proximate the first side wall toward a sill defined by the second side wall;
at least one foil at
least partially submerged in the water near at least one of the first side
wall and the second
side wall, and being adapted for movement by a moving mechanism in a direction
along the
side wall for generating at least one wave in the channel that forms a
breaking wave on the
sill; a passive flow control mechanism to mitigate a mean flow of the water
induced by the
movement of the at least one foil in the direction along the side wall; a
passive current control
gutter mechanism to mitigate currents in the water induced by the movement of
the at least
one foil in the direction along the side wall; and a passive chop control
mechanism to mitigate
random chop and seich in the water at least partially induced by the movement
of the at least
one foil in the direction along the side wall, and at least partially induced
by a shape and the
contour of the channel.
1000911 According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool having a bottom that
slopes upward
from a deep area toward a sill defined by the second side wall; a track
positioned in the pool
substantially parallel to the sill; a moving vehicle that moves on the track;
at least one foil
coupled with the moving vehicle and at least partially submerged in the water
of the pool,
each of the at least one foil having a curvilinear cross-sectional geometry
that includes a
leading surface that is concave about a vertical axis to provide drag and
being adapted for
movement by a moving mechanism in a direction along the track for generating
at least one
wave in the water near the sill, and a trailing surface that narrows from a
maximum width of
the foil adjacent the leading surface to a point at an end of the foil, the
trailing surface to
decrease the drag of the foil and to minimize oscillatory waves that trail the
primary wave
from the water moving past the leading surface of the foil; and one or more
immovable
passive flow control mechanisms positioned in the pool proximate the sill and
formed to
counter a mean flow of the water induce by the movement of the at least one
foil in the
direction along the track to mitigate the mean flow of the water in the pool.
[0009g] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool having at least a side
wall, and a
bottom with a contour that slopes upward from a deep area proximate the side
wall toward a
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sill defined by a beach that forms an edge of the pool; a track positioned in
the deep area of
the pool substantially parallel to the sill; a moving vehicle that moves on
the track; at least one
foil coupled with the moving vehicle and at least partially submerged in the
water of the pool,
each of the at least one foil having a curvilinear cross-sectional geometry
that includes a
leading surface that is concave about a vertical axis to provide drag and
being adapted for
movement by a moving mechanism in a direction along the track for generating
at least one
wave in the water near the sill, and a trailing surface that narrows from a
maximum width of
the foil adjacent the leading surface to a point at an end of the foil, the
trailing surface to
decrease the drag of the foil and to minimize oscillatory waves that trail the
primary wave
from the water moving past the leading surface of the foil; and a gutter
formed between the
sill and the beach to counter currents in the water induced by the movement of
the at least one
foil in the direction along the side wall to mitigate the currents of the
water in the pool.
[0009h] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool having at least a
sidewall, a deep area
and a contour that slopes upward from the deep area toward a sill and a beach
that forms an
edge of the pool; a track positioned in the deep area of the pool
substantially parallel to the
sill; a moving vehicle that moves on the track; at least one foil coupled with
the moving
vehicle and at least partially submerged in the water of the pool, each of the
at least one foil
having a curvilinear cross-sectional geometry that includes a leading surface
that is concave
about a vertical axis to provide drag and being adapted for movement by a
moving mechanism
in a direction along the track for generating at least one wave in the water
near the sill, and a
trailing surface that narrows from a maximum width of the foil adjacent the
leading surface to
a point at an end of the foil, the trailing surface to decrease the drag of
the foil and to
minimize oscillatory waves that trail the primary wave from the water moving
past the leading
surface of the foil; and a passive chop and seich control mechanism positioned
proximate the
beach to immovably counter random chop and seich in the water at least
partially induced by
the movement of the at least one foil in the direction along at least one of
the first side wall
and the second side wall, and at least partially induced by a shape and the
contour of the pool.
10009i] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a side wall
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and a bottom with a contour that slopes upward from a deep area proximate the
side wall
toward a sill; at least one foil at least partially submerged in the water
near the side wall, each
of the at least one foil having a curvilinear cross-sectional geometry that
includes a leading
surface that is concave about a vertical axis to provide drag and being
adapted for movement
by a moving mechanism in a direction along the side wall for generating at
least one wave in
the channel near the sill, and a trailing surface that narrows from a maximum
width of the foil
adjacent the leading surface to a point at an end of the foil, the trailing
surface to decrease the
drag of the foil and to minimize oscillatory waves that trail the primary wave
from the water
moving past the leading surface of the foil; and one or more immovable passive
flow control
mechanisms positioned in the channel proximate the sill and formed to counter
a mean flow of
the water induced by the movement of the at least one foil in the direction
along the side wall
to mitigate the mean flow of the water in the channel.
1000911 According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a side wall
and a bottom with a contour that slopes upward from a deep area proximate the
side wall
toward a sill defined by a beach that forms an edge of the channel; at least
one foil at least
partially submerged in the water near the side wall, and being adapted for
movement by a
moving mechanism in a direction along the side wall for generating at least
one wave in the
channel that forms a breaking wave on the sill, each of the at least one foil
having a
curvilinear cross-sectional geometry that includes a leading surface that is
concave about a
vertical axis to provide drag to generate a primary wave laterally in water
that contacts the
leading surface of the foil, and a trailing surface that narrows from a
maximum width of the
foil adjacent the leading surface to a point at an end of the foil, the
trailing surface to
decreases the drag of the foil and to minimize oscillatory waves that trail
the primary wave
from the water moving past the leading surface of the foil; and a gutter
formed between the
sill and the beach to counter currents in the water induced by the movement of
the at least one
foil in the direction along the side wall to mitigate the currents of the
water in the channel.
[0009k] According to another aspect of the present invention, there is
provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a side wall
and a bottom with a contour that slopes upward from a deep area proximate the
side wall
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toward a sill; a beach that forms an edge of the channel; at least one foil at
least partially
submerged in the water near the side wall, and being adapted for movement by a
moving
mechanism in a direction along the side wall for generating at least one wave
in the channel
that forms a breaking wave near the sill, each of the at least one foil having
a curvilinear
cross-sectional geometry that includes a leading surface that is concave about
a vertical axis to
provide drag to generate a primary wave laterally in water that contacts the
leading surface of
the foil, and a trailing surface that narrows from a maximum width of the foil
adjacent the
leading surface to a point at an end of the foil, the trailing surface to
decrease the drag of the
foil and to minimize oscillatory waves that trail the primary wave from the
water moving past
the leading surface of the foil; and a passive chop and seich control
mechanism positioned
proximate the beach to immovably counter random chop and seich in the water at
least
partially induced by the movement of the at least one foil in the direction
along the side wall,
and at least partially induced by a shape and the contour of the channel.
1000911
According to another aspect of the present invention, there is provided a wave
pool comprising: a pool for containing water, the pool defining a channel
having a side wall
and a bottom with a contour that slopes upward from a deep area proximate the
side wall
toward a sill; at least one foil at least partially submerged in the water
near the side wall, and
being adapted for movement by a moving mechanism in a direction along the side
wall for
generating at least one wave in the channel that forms a breaking wave near
the sill, each of
the at least one foil having a curvilinear cross-sectional geometry that
includes a leading
surface that is concave about a vertical axis to provide drag to generate a
primary wave
laterally in water that contacts the leading surface of the foil, and a
trailing surface that
narrows from a maximum width of the foil adjacent the leading surface to a
point at an end of
the foil, the trailing surface to decrease the drag of the foil and to
minimize oscillatory waves
that trail the primary wave from the water moving past the leading surface of
the foil; a
passive flow control mechanism positioned in the channel proximate the sill
and formed to
immovably counter a mean flow of the water induced by the movement of the at
least one foil
in the direction along the side wall to mitigate the mean flow of the water in
the channel; a
passive current control gutter mechanism proximate the sill and formed to
immovably counter
currents in the water induced by the movement of the at least one foil in the
direction along
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the side wall to mitigate the currents of the water in the channel; and a
passive chop control
mechanism to mitigate random chop and seich in the water at least partially
induced by the
movement of the at least one foil in the direction along the side wall, and at
least partially
induced by a shape and the contour of the channel.
[0010] The details of one or more embodiments are set forth in the
accompanying
drawings and the description below. Other features and advantages will be
apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other aspects will now be described in detail with
reference to the
following drawings.
[0012] FIG. 1 depicts properties of waves entering shallow water.
[0013] FIG. 2 illustrates four general types of breaking waves.
[0014] FIGS. 3A and 3B are a top and side view, respectively, of a pool
having an
annular shape.
[0015] FIG. 4 illustrates an embodiment of a bottom contour of a pool.
[0016] FIG. 5 illustrates an embodiment of a pool in an annular
configuration, and a
wave generator on an inner wall of the pool.
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[0017] FIG. 6 illustrates an embodiment of a section of a pool in an
annular
configuration having a wave generator arranged vertically along an outer wall.
[0018] FIGS. 7A and 7B are a perspective view and cross-sectional view,
respectively, to illustrate an embodiment of a shape of a foil for a linear
section of wall.
[0019] FIG. 8A illustrates a section of an embodiment of a foil 500
including an
eccentric roller.
[0020] FIG. 8B and 8C illustrate an embodiment of a foil 500 with several
morphing
rollers.
[0021] FIG. 9 shows the relative geometry of the velocity of the wave
propagation
with respect to the foil velocity.
[0022] FIG. 10 illustrates an embodiment of a wave generator pool in which
a
rotating inner wall is positioned within a fixed outer wall.
[0023] FIG. 11 illustrates an embodiment of a wave generator in which a
flexible
layer is placed on an outer wall, and the outer wall includes a number of
linear actuators for
being arranged around the entire length or circumference of the outer wall.
[0024] FIG. 12 illustrates an embodiment of a wave generator having a
flexible layer
placed on an outer wall.
[0025] FIG. 13 illustrates an embodiment of a wave generator that includes
a flexible
layer that can be raised away from the outer wall to define a foil.
[0026] FIG 14 illustrates an embodiment of vortex generators having
elongated
members with a square cross section.FIG. 15 illustrates another embodiment of
a vortex
generator having squared members spaced-apart both width-wise and length-wise.
[0027] FIG. 16 illustrates an embodiment of vortex generators mounted both
on a
bottom section adjacent to an outer gutter of the basin, and on a lower
portion of an outer
gutter wall of the basin.
[0028] FIG. 17 illustrates an embodiment of vortex generators having non-
linear
shapes, such as being angled or curved.
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[0029] FIG. 18 illustrates an embodiment of a smooth (curved) pool profile
where the
vortex generators meet the side walls or floor.
[0030] FIG. 19 illustrates an embodiment of at least a part of the cavity
near the inner
island of the pool being fitted with a series of angled vanes.
[0031] FIG. 20 shows an embodiment of a pool having both an inside gutter
system
and an outside gutter system between the foil and wave generation mechanism
and the outer
wall of the basin.
[0032] FIG. 21 illustrates an embodiment of a flow redirection gutter
system on a
sloping beach.
[0033] FIG. 22 illustrates an embodiment of implementations of gutters
and/or baffles
that can be used as a perforated wall.
[0034] FIG. 23 illustrates an example of a time evolution of a resulting
wave from a
moving foil, including an incident wave and reflected wave(s).
[0035] FIG. 24 illustrates an embodiment of a gutter having vertical slots
in the gutter
wall.
[0036] FIG. 25 illustrates an embodiment of a gutter having vertical slots
in the gutter
wall and a non-perforated step.
[0037] FIG. 26 illustrates an embodiment of a gutter system having porous
walls
integrated with vortex-generating roughness elements.
[0038] Like reference symbols in the various drawings indicate like
elements
DETAILED DESCRIPTION
[0039] This document describes an apparatus, method, and system to generate
waves
of a desired surfability. Surfability depends on wave angle, wave speed, wave
slope (i.e.
steepness), breaker type, bottom slope and depth, curvature, refraction and
focusing. Much
detail is devoted to solitary waves as they have characteristics that make
them particularly
advantageous for generation by the apparatus, method and system presented
here. As used
herein, the term "solitary wave" is used to describe a shallow water wave, or
"surface gravity
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wave" having a single principal displacement of water above a mean water
level. A solitary
wave propagates without dispersion. It very closely resembles the type of wave
that produces
favorable surf in the ocean. A theoretically-perfect solitary wave arises from
a balance
between dispersion and nonlinearity, such that the wave is able to travel long
distances while
preserving its shape and form, without obstruction by counteracting waves. A
wave form of
a solitary wave is a function of distance x and time t, and can be
characterized by the
following equation:
11 3A
ti(x,t)= A sec ho2 ¨ t g(ho + A))
4h
0
where A is the maximum amplitude, or height, of the wave above the water
surface, ho is the
depth of the water, g is the acceleration of gravity and ri(x,t) is the height
of the water above
ho. The length of a solitary wave, while theoretically infinite, is limited by
water surface
elevation, and can be defined as:
L ______________________ where k= 1,13A3
4170
[0040] POOLS
[00411 The systems, apparatuses and methods described herein use a pool of
water in
which solitary type or other surface gravity waves are generated. In some
preferred
implementations, the pool can be circular or annular, being defined by an
outer wall or edge
that has a diameter of 200 to 800 feet or more. Alternatively, a round or
circular pool having
a diameter of less than 200 feet can be used, however, a diameter of 450 to
550 feet may be
preferred. In one exemplary implementation, the pool can be annular with a
center circular
island that defines a channel or trough. In this annular configuration, the
pool has an outer
diameter of 550 feet and a channel width of at least 50 feet, although the
channel can have a
width of 150 feet or more, which can yield 30-100 feet of rideable wave
length.
[00421 In another exemplary implementation, the pool can be a contiguous
basin such
as a circular pool without a center island. In the circular configuration, the
pool can have a
bottom that slopes up toward the center to a shoal or sill, and may include a
deeper trough or
lead to a shallow sill or flat surface. In yet other implementations, the pool
can be any
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closed-loop, curvilinear channel, such as a racetrack shape (i.e. truncated
circle), oval, or
other rounded shape. In still other implementations, the pool can include an
open or closed
looped linear or curvilinear channel through which water is flowed (such as a
crescent shape
or a simple linear canal), and which may or may not use a water recapture or
recirculation
and flow mechanism.
[0043] FIGS. 3A and 3B are top and cross-sectional views, respectively, of
a pool 100
in accordance with an annular implementation. Pool 100 has a substantially
annular shape
that is defined by an outer wall 102, an inner wall 104, and a water channel
106 between and
defined by the outer wall 102 and the inner wall 104. In annular
implementations, the outer
wall 102 and inner wall 104 may be circular. The inner wall 104 can be a wall
that extends
above a mean water level 101 of the water channel 106, and can form an island
108 or other
type of platform above the mean water level 101. The inner wall 104 may also
be inclined so
as to form a sloping beach. Alternatively, the inner wall 104 may form a
submersed reef or
barrier between the water channel 106 and a second pool. For example, the
second pool can
be shallow to receive wash waves resulting from waves generated in the water
channel 106.
Pool 100 can further include a side 110 which, according to some
implementations, can
include a track such as a monorail or other rail for receiving a motorized
vehicle. In addition,
the vehicle can be attached to at least one wave generator, preferably in the
form of a
movable foil, as will be described further below. In some implementations,
outer wall 102,
with or without cooperation with the side 110, can host a wave generator in
the form of a
flexible wall or rotating wall with built-in foils, as will also be described
further below.
100441 WAVE GENERATOR
[0045] FIG. 4 illustrates a bottom contour of a pool having a critically-
sloped beach
design. The bottom contour of the pool having the critically-sloped design may
be
implemented in any number of shaped pools, including pools that are linear,
curvilinear,
circular, or annular. The bottom contour can include a side wall 200 which can
be an inner
side wall or an outer side wall. The side wall 200 can have a height that at
least extends
higher than a mean water level, and can extend above a maximum amplitude, or
height, of a
generated wave. The side wall 200 can be adapted to accommodate a wave
generator, such
as a foil that is vertically placed on the side wall 200 and moved laterally
along the side wall
200. The bottom contour can further include a deep region 202, which in some
configurations extends at least long enough to accommodate the thickness, or
height, of the
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foil. The intersection of the side wall 200 and the deep region 202 may also
include a slope,
step or other geometrical feature, or a track/rail mechanism that participates
in guiding or
powering the motion of the foil. A swell can be produced to have an amplitude
up to the
same or even greater than the depth of the deep region 202.
[0046] The bottom contour of the pool can further include a slope 204 that
rises
upward from the deep region 202. The slope 204 can range in angle from 1 to 16
degrees,
and also from 5 to 10 degrees. The slope 204 can be linear or curved, and may
include
indentions, undulations, or other geometrical features. The bottom contour can
further
include a shoal 206 or sill. The surface from a point on the slope 204 and the
shoal 206 can
provide the primary break zone for a generated wave. Wave setup in the break
zone can
change the mean water level. The shoal 206 can be flattened or curved, and can
transition
into a flattened shallow planar region 208, a shallow trench 210, or a deep
trench 212, or any
alternating combination thereof. The basin side opposite the wave generator
ultimately ends
in a sloping beach.
[0047] The shoal 206 can also be an extension of the slope 204 and
terminate directly
into a beach. The beach may be real or artificial. The beach may incorporate
water
evacuation systems which can include grates through which the water can pass
down into.
The wale' evacuation systems may be linked to the genet al water teenculatiou
and/or
filtering systems, any may incorporate more advanced flow redirection
features. The beach
may also incorporate wave damping baffles that help to minimize the reflection
of the waves
and reduce along shore transport and currents.
[0048] The bottom contour can be formed of a rigid material and can be
overlaid by a
synthetic coating. In some implementations, the bottom may be covered with
sections of
softer more flexible materials, for example a foam reef or covering may be
introduced that
would be more forgiving during wipeouts. For example, the coating can be
thicker at the
shoal 206 or within the break zone. The coating can be formed of a layer that
is less rigid
than the rigid material used for the bottom contour, and may even be shock
dampening. The
slope 204, shoal 206 and/or other regions of the bottom contour can be formed
by one or
more removable inserts. Further, any part of the bottom contour may be
dynamically
reconfigurable and adjustable, to change the general shape and geometry of the
bottom
contour. For example, the bottom contour may be changed on-the-fly, such as
with the
assistance of motorized mechanics, inflatable bladders, simple manual
exchange, or other
8
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similar dynamic shaping mechanisms. In addition, removable inserts or modules
can be
connected with a solid floor making up a part of the pool, including the
bottom contour. The
inserts or modules can be uniform about the circle, or variable for creating
recurring reefs
defined by undulations in the slope 204 or shoal 206. In this way particular
shaped modules
can be introduced at specific locations to create a section with a desirable
surf break.
[0049] FIG. 5 illustrates a pool 300 in an annular configuration, and a
wave generator
302 on an inner wall 304 of the pool 300. The wave generator 302 can be a foil
arranged
vertically along the inner wall 304, and moved in the direction 303 indicated
to generate a
wave W. FIG. 6 illustrates an example section of a pool 400 in an annular
configuration
having a wave generator 402 arranged vertically along an outer wall 404. The
wave
generator 402 can be moved in the direction 403 indicated, to generate a wave
W as shown.
In some implementations, the outer wall 404 placement of the wave generator
402 can enable
improved focusing and larger waves than an inner wall placement. Additionally,
in some
implementations, inner wall placement can enable reduced wave speed and
improved
surfability. The wave generators 302 and 402 can be moved by a powered vehicle
or other
mechanism that is generally kept dry and away from the water, such as on a
rail or other
track, part of which may be submerged. In some implementations the entire rail
can rotate,
allowing for the possibility of keeping the drive motors in the non-rotating
frame.
[0050] The wave generators may also be configured to run in the center of
the
channel in which case there would be beaches on both the inner and outer walls
and the
track/rail mechanism would be supported either from an overhead structure or
by direct
attachment to the floor of the pool.
[0051] FOILS
[0052] Some implementations of the wave pools described herein can use one
or
more foils for generating waves of a desired surfability. The foils can be
shaped for
generating waves in supercritical flow, i.e. the foils move faster than the
speed of the
generated waves. This can allow for significant peel angle as the wave is
inclined with the
radius. The speed of a wave in shallow water (when the water depth is
comparable to the
wave length) can be represented by Vw:
V. = g(ho +A)
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where g is the force of gravity, and 110 is the depth of the water and A in
the wave amplitude.
Criticality can be represented by the Froude number (Fr), in which a number
greater than 1 is
supercritical, and a number less than 1 is subcritical:
Fr =17F ' where VF is the velocity of the foil relative to
the water
V,
[0053] The foils can be adapted to propagate the wave away from a leading
portion of
the foil as the water and foil move relative to each other. This movement may
be able to
achieve the most direct transfer of mechanical energy to the wave. In this
manner, ideal
swells can be formed immediately adjacent to the leading portion of the foil.
The foils can be
optimized for generating the largest possible swell height for a given water
depth. However,
some foils can be configured to generate smaller swells.
[0054] In order to achieve the best energy transfer from the foil to the
wave and to
ensure that the generated swell is clean and relatively solitary, the foils
can be designed to
impart a motion to the water that is close to a solution of a known wave
equation. In this way
it may not be necessary for the wave to have to form from a somewhat arbitrary
disturbance
as is done with some other wave generation systems. The proposed procedure can
rely on
matching the displacement imparted by the foil at each location to the natural
(theoretical)
displacement field of the wave. For a fixed location through which the foil
will pass P, the
direction normal to the foil can be x and the thickness of the part of the
foil currently at P can
be X(t).
[0055] The rate of change of X at the point P may be matched with the depth
averaged velocity of the wave i7. This can be shown expressed in equation (1).
¨dX = rt(X ,t) (1)
dt
Applying the change of variable from (x,t) to (0 = ct ¨ X,t) where c is the
phase
speed of the wave.
dX = 17(0(X))
(2)
de c ¨17(9(X))
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[00561 In equation (2) the depth averaged velocity of the wave t7 can be
given by any
of a number of different theories. For the case of solitary waves, which
generally take the
form of equation 3 and 4 below, several examples can be provided. This
technique of foil
design may also apply to any other form of surface gravity wave for which
there is a known,
computed, measured or approximated solution.
r1(0)= Asec h2 (f30 2) (3)
cri(0)
Ft(0) = (4)
h, + 77(0)
Here ti(0) is the frcc surface elevation from rest, A is thc solitary wave
amplitude, h, is thc
mean water depth, /3 is the outskirts decay coefficient, c is the phase speed,
and Ft (0) is the
depth averaged horizontal velocity. C and 13 can differ for different solitary
waves.
[00571 Combining equations (2) and (3) with (4) can give the rate of change
of the
foil thickness in time at a fixed position (5), and can be related to the foil
shape X(Y),
through the foil velocity VF, by substituting t= WVF
X(t) = ¨2Atanh[fi(ct ¨ X(t))/ (5)
hof3
A maximum thickness of foil can be given from (5) as:
4A
¨ ¨
hof3
The length of the active section of the foil can then be approximated as:
4 I A
=- tanii + ¨
fic ho
Values for C and f3 corresponding to the solitary wave of Rayleigh can be:
i3R 1,1 3A
and c, = g(A + h0)
2 4h02 (A + ho)
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In this example for small displacements after linearization the foil shape
X(Y), can be
approximated as.
2A h, tanh(0,c,Y/ 217,)
hoi3R h, + A[1¨ tanh2(J6õcRY/2V,,)]
This solution can also be approximated with a hyperbolic tangent function.
These foil shapes,
as described by at least some of the mathematical functions, would have
extremely thin
leading edges which would be structurally unstable. The actual leading edges
would be
truncated at a suitable thickness typically of 3-12 inches, and rounded to
provide a more rigid
leading edge. The rounding may be symmetrical or not and in some
implementations may
loosely follow the shape of an ellipse.
[0058] As shown in an exemplary configuration in FIGS. 7A and 7B, the foils
500 are
three-dimensiunal, curvilinear shaped geometries having a leading surface 502,
or "active
section X(Y)," that generates a wave, and a trailing surface 504 that operates
as a flow
recovery to avoid separation of the flow and to decrease the drag of the foil
500 for improved
energy efficiency. The foil 500 is shown by way of example as configured for
towing in a
linear canal and hence has a flat surface which would be adjacent to the
vertical wall of the
canal. The foil 500 can be shaped to get most of the energy into the primary,
solitary wave
mode, and minimize energy into oscillatory trailing waves. As such, the foil
500 can promote
a quiescent environment for a following wave generator and foil, if any. Each
foil 500 may
contain internal actuators that allow its shape to morph to produce different
waves, and/or can
articulate so as to account for changes in curvature of the outer wall in non-
circular or non-
linear pools. In some implementations the morphing of the foil 500 can allow
for the
reversal of the mechanism to generate waves by translating the foil 500 in the
opposite
direction. The morphing can be accomplished by a series of linear actuators or
by fitting
several vertical eccentric rollers 552 (as shown in FIGS. 8A-8C) under the
skin of the wave
generating face of the foil 500. A sketch of a foil 500 including an eccentric
roller 552 is
shown in FIG 8A. The skin of the wave generating face of the foil 500 is shown
in FIG. 8A
as being transparent for purposes of showing the eccentric roller 552. In
addition, a foil 500
with several morphing rollers 552 is shown in FIG 8B, 8C. Similar to FIG. 8A,
the skin of
the wave generating face of the foil 500 is shown in FIG. 8C as being
transparent for
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purposes of showing the several morphing rollers 552. Rollers 552 can also be
added in the
location of the foil 500 having either the maximum thickness or the recovery.
In some
implementations of the foil 500, the flexible layer may be formed as a
relatively rigid sheet
that slides horizontally as the foil changes shape. In addition, some
implementations may
include a specific fixture consisting of a slotted grove that can take up the
slack in the
relatively rigid sheet through spring or hydraulic tension devices that
stretch the relatively
rigid sheet along the length of the foil 500. The ability to morph the shape
of the foil 500 can
allow for large variation in the size and shape of the generated swells, and
allow for
optimization of the foil 500 shape to generate the desired swell shape. This
fine optimization
can be necessary due to other viscous fluid mechanical phenomenon at play in
the boundary
layer that develop over the surface of the foil 500. The attached boundary
layer can have the
effect of slightly changing the effective shape of the hydrofoil. In other
implementations
there may be specific surface roughness or "a boundary layer trip" installed
on the surface of
the hydrofoil. In particular, the physical length of the hydrofoils may be
reduced if sufficient
turbulence is generated on the recovery section to ensure there is no flow
separation, and the
strongly turbulent boundary layer will not be separated so easily in an
adverse pressure
gradient.
[0059] In some implementations, the foils 500 are shaped and formed to a
specific
geometry based on a transformation into a function of space from an analogy to
an equation
as a function of time. Hyperbolic tangent functions that mathematically define
the stroke of a
piston as a function of time, such that the piston pushes a wave plate to
create a shallow water
wave that propagates away from the wave plate. These hyperbolic tangent
functions consider
the position of the wave plate relative to the position of the generated wave
in a long wave
generation model, and produce an acceptable profile for both solitary and
cnoidal waves.
1 hese techniques can be used to generate any propagating surface gravity wave
accounting
for the propagation of the wave away from the generator during generation
(i.e. adapt to how
the wave is changing during generation). Compensation for movement of the
generator over
time and the specific shape of the recovery section can assist in removing
trailing oscillatory
waves, which can provide a more compact and efficient generation process.
Other types of
waves to those discussed here can be defined.
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[0060] The thickness of the foil can be related to the amplitude (height)
of the wave
and the depth of the water. Accordingly, for a known depth and a desired
amplitude A, it can
be determined that a thickness of the foil, FT, can be given approximately by:
For a Rayleigh solitary wave:
F = 4.\IA(A k )
3
For a Boussenesq solitary wave:
-F 411Ak
3
For shallow water, second order solitary wave:
F =4liA(A+11,)/1+ A\
3
\ 0)
100611 FIG. 9 shows a cross-sectional geometry of a foil 600. As a three-
dimensional
object, the foil 600 can generate a wave having a propagation velocity and
vector Vw, based
on the speed and vector of the foil V. As the foil moves in the direction
shown, and
dependent on its speed, the wave will propagate out at a peel angle a, given
by sin a = Fr-1 ,
so for a given water depth and wave height the peel angle can be determined by
the speed of
the foil, with larger speeds corresponding to smaller peel angles. The smaller
the peel angle,
the longer the length of the wave crest will be across the pool.
[0062] FIG. 10 illustrates a wave generator 700 in which a rotating inner
wall 702 is
positioned within a fixed outer wall 706. The rotating inner wall 702 can be
equipped with
one or more fixed foils 704 that can be the same size and shape as the foils
described above.
These embedded foi1s704 may have internal actuators708 which can assist in
allowing the
embedded foils 704 to morph and change shape, such as according to a variety
of the cross-
sectional shapes described above. The change in cross-sectional shapes can
accommodate
"sweet spots" for different speeds and water depths. These actuators can
function is a way
similar to the morphing eccentric rollers shown in FIG. 8.
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[00631 FIG. 11 illustrates a wave generator 800 in which a flexible layer
802 is placed
along an outer wall 804, and the outer wall 804 can include a number of linear
actuators 806
arranged around at least a majority of the length or circumference of the
outer wall 804. In
addition, the linear actuators 806 can also be attached to the flexible layer
802. The flexible
layer 802 can be formed out of any number of flexible materials, including
rubber or
materials similar to rubber. The linear actuators 806 can be mechanical or
pneumatic
actuators, or other devices that have at least a radial expansion and
retraction direction, such
as a series of vertically aligned eccentric rollers. The linear actuators 806
can be actuated in
order to form a moving shape in the flexible layer 802 that approximates the
shape of the
foils as described above. The foil shape can propagate along the outer wall
804 or flexible
layer 802 at a velocity VI.
[00641 FIG. 12 illustrates an implementation of a wave generator 900
including a
flexible layer 902 positioned along an outer wall 904. The gap in-between the
flexible layer
902 and the outer wall 904 can define a moving foil 906, similar to as
described above, and
can includes one or more rollers 908 in tracks that can connect to both the
outer wall 904 and
flexible layer 902. The rollers 908 in tracks can allow the foil 906 formed in
the gap to travel
smoothly in a direction along the outer wall 904. This moving foil 906 can
produce a radial
motion of the flexible layer 902 that at least closely approximates the shapes
of one or more
foils described above.
[0065] FIG. 13 illustrates a wave generator 1000 that includes a flexible
layer 1002
that can be raised away from the outer wall 1004 to define a foil 1006. The
foil 1006 can
include internal actuators or eccentric rollers 1010 that allow it to morph
the shape of the foil
1006, which may change depending on the direction of movement along the outer
wall 1004.
The defined foil 1006 can move via rollers 1008 on tracks, such as those
described above.
Accordingly, the flexible layer 1002 can be shaped to approximate the foils
described above
while shielding actuators and rollers 1008 on tracks from water. This
configuration may also
diminishing the risk of a separate moving foil in which body parts can be
caught.
[00661 VIRTUAL BOTTOM
[00671 In some implementations, a system of jets positioned near the bottom
of the
pool on the slope can simulate the water being shallower than it actually is
which can allow
the wave to break in deeper water than what could otherwise be achieved. These
jets may be
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positional so as to generate both mean flow and turbulence at a required
level. The
distribution of these jets may change both radially and in the direction from
the outer wall
towards the beach with more jets on the beach. There may also be azimuthal
variation in the
nature and quantity of the jets. This jet system may be incorporated with both
the filtering
system and the wave system to provide mean flow or lazy river mitigation.
Roughness
elements may be added to the bottom of the pool to promote the generation of
turbulence that
may promote changes in the form of the breaking wave. The distribution and
size of the
roughness elements can be a function of both radius and azimuth. The roughness
elements
may take the form of classical and novel vortex generators and are described
below.
[0068] MEAN FLOW
[0069] A moving foil or set of foils within a pool, particularly a
circular basin as
described above, will eventually generate a mean flow or "lazy river" effect,
where water in
the pool will develop a slight current in the direction of the one or more
moving foils.
[0070] In other implementations, a pool can include a system to provide or
counter a
mean flow or circulation. The system may include a number of flow jets through
which
water is pumped to counter or mitigate any "lazy river" flow created by the
moving foils,
and/or help to change the shape of the breaking wave. The mean circulation may
have
vertical or horizontal variability. Other mean flow systems may be used, such
as a counter-
rotational opposing side, bottom or other mechanism.
[0071] PASSWE "LAZY RIVER" FLOW CONTROL
[0072] FIGS. 14-16 illustrate various passive mechanisms that can be added
to select
surfaces of the pool, particularly in the deep area under and beside the foil,
as turbulence-
generating obstacles to the mean flow of azimuthal and radial currents which
can mitigate the
mean flow induced by the moving foils.
[0073] In some implementations, as shown in FIG. 14, a number of vortex
generators
1302 are provided to a surface 1304 of a pool, such as on a bottom of the pool
or a side wall
of the basin. The vortex generators 1302 can be placed in areas behind a
safety fence at an
outer side of the pool proximate the moving foils, such as where surfers will
not likely come
into contact with them. Alternatively or in addition, vortex generators 1302
can be placed in
the basin surface of the pool where surfing takes place, especially if the
vortex generators
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1302 are part of a safety feature, such as being made out of a soft material
such as foam to
protect against impact to the surface by a surfer. The vortex generators 1302
can be
positioned and spaced apart incrementally on the surface 1304, such as a floor
of the basin of
the pool, as shown in FIGS. 14 and 15, and/or can be positioned on the side
wall of the pool,
as shown in FIG 16.
[0074] FIG. 14 illustrates an implementation of vortex generators 1302
having
elongated members with a square cross section. Additionally, the vortex
generators can be
spaced-apart at an increment, such as a space of 8 times the cross-sectional
width k of each
vortex generator 1302 (p, ---8k). FIG. 15 illustrates another implementation
of a vortex
generator 1306 having squared members spaced-apart both width-wise (i.e., 8
times the
cross-sectional width k), and length-wise (i.e. every other cross-sectional
length, pz=2k).
FIG. 16 illustrates vortex generators 1302 mounted both on a bottom section
adjacent to an
outer gutter 1310 of the basin, and on a lower portion of an outer gutter wall
1312 of the
basinsuch generators may also be implemented on the actual outer wall if there
is no gutter,
or when the gutter system does not extend to the full depth... Rectangular
members may
also be used in which case the spacing would be approximately 8 times the
azimuthal width
of the members. As illustrated in FIG. 17, vortex generators 1330 can also
have non-linear
shapes, such as being angled or curved. In the case of angled vortex
generators, they may be
positioned with their point toward either the upstream or downstream
directions of the
movement of the foils and the resultant mean flow.
[0075] The interactions between the mean flow with the vortex generators
can
increase the Reynolds stresses and overall turbulence intensity in the
vicinity of the hydrofoil
path which can provide for thicker boundary layers in the water. These
enhanced boundary
layers can dissipate substantially more energy than an equivalent-sized smooth
surface.
Additionally, the transport of momentum by turbulent diffusion, specifically
associated with
the larger vortices, can allow the basin floor or wall areas covered with the
vortex generators
to provide strong sinks for both azimuthal and radial momentum. In effect
these elements can
allow the fluid within the basin to better transmit a torque to the basin
itself.
[0076] While each vortex generator can have a squared cross section, as
shown in
FIGS. 14, 15, 16 and 17, other cross-sectional shapes can also be used, such
as rounded,
rectangular, or other prisms or three dimensional shapes. In some preferred
implementations,
each vortex generator has cross-sectional dimensions of approximately 1 foot
square,
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although side dimensions of less than 1 foot or greater than 1 foot can also
be used. The
vortex generators can be preferably spaced apart 6-12 ft. For example, if used
on a bottom
surface of the pool, the vortex generators can be spaced apart along radial
lines, at an average
azimuthal spacing of 6 to 12 feet. If positioned on a vertical sidewall of the
pool, the vortex
generators can be spaced apart uniformly. Still in other variations, spacing
of vortex
generators can be varied around the pool so as to achieve different effects.
[0077] In order to facilitate cleaning of the vortex generators and pool,
and to avoid
the collection of debris in the corners in and around the vortex generators,
some
implementations may opt for smooth (curved) pool profiles 1500 where the
vortex generators
meet the side walls or floor, as shown by way of example in FIG. 18.
[0078] In some implementations, the vortex generators can be formed out of
a rigid or
solid material and can be permanently affixed to the pool. For example, the
vortex generators
may be made of concrete reinforced with rebar and integrated into the basin
structure. In
other implementations, the vortex generators may be modular and attached with
bolts, or
constructed of plastic, carbon fiber, or other less rigid or solid material.
These modular
vortex generators can also allow for custom configuration of variable spacing,
sizes and
orientation. For instance, various combinations and arrangements of fixed and
modular
vortex generators may be employed.
[0079] GUTTER SYSTEM TO COUNTER AZIMUTHAL CURRENTS (VANED
CAVITY GUTTERS)
[0080] The previously discussed systems, such as vortex generators,
roughness
enhancement and other protrusions or flaps, can be configured to reduce lazy
river flows by
increasing turbulent dissipation within the flow. Additionally, these systems
can act as a sink
or inhibitor for both the mean azimuthal/longitudinal momentum and also the
alternating
currents in the radial/transverse and vertical directions. Alternatively, or
additionally,
azimuthal/longitudinal flow can be redirected by a gutter system employed at
an inner beach
area of the circular, crescent shaped or linear basin ("inside gutter
system"), at an outer wall
of the basin ("outer gutter system"), or both. The basic principal of these
flow redirection
gutters can be to capture the kinetic energy of the flow as potential energy
by running it up a
slope. The fluid can then be returned to the basin with a different velocity
vector direction to
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that with which it arrived. This redirection can be accomplished with a system
of vanes, but
other means such as tubes or channels can also be implemented.
[0081] In some implementations, the gutter system includes a sloped floor
overlaid by
a water-permeable, perforated grate, typically of 25-40% open area. In this
case for an inside
(sloped beach) gutter system, the slope of the grating can be greater than the
slope of the
angled floors or beach, forming a cavity between the sloped floor of the beach
and the more
steeply sloped grating that extends around the center island in the basin. For
a 500ft diameter
circular wave pool with wave generation around the outer perimeter, the cavity
may extend
20-40 ft away from the island with the bottom floor being sloped at
approximately 5-9
degrees and the perforated gratings forming the top cover of the cavity being
sloped at
approximately 10-20 degrees. The slopes may be chosen differently for smaller
or larger
pools, with larger pools requiring less steep slopes and smaller pools
requiring a somewhat
steeper slope.
[0082] This cavity alone can absorb wave energy and reduce reflected waves
generated from the movement of the foil around the basin. Additionally, the
cavity can
reduce the azimuthal currents near the sloped beach through simple dissipative
mechanisms
as water entering through the gratings may encounter enhanced turbulence. For
a circular
wave pool implementation, the impoi (affix of 'educing the cull ems Heal the
central island
cannot be overstated. When there are significant currents parallel to the
shore in the direction
that the wave is breaking the currents can allow the wave to "overtake itself'
requiring the
wave generating mechanism to move at a higher speed if the form of the wave
barrel is to be
preserved. It is these currents that can tend to limit the minimum operational
speed of the
wave, whether it is generated by a hydrofoil type system or some other type of
wave
generator. This minimum operational speed where the wave will no longer barrel
but instead
presents itself as a foamy crest of white water is associated with a condition
that has been
dubbed "foam-balling".
[0083] In other implementations, and as illustrated in FIG. 19, at least a
part of the
cavity near the inner island 1402 can be fitted with a series of angled vanes
1404. The angled
vanes 1404 can be formed out of a solid material, such as concrete, or any
number of a
variety of solid materials. The angled vanes 1404 can be overlaid by a water-
permeable
perforated grate 1406. The perforated grate 1406 is shown in FIG. 19 as being
transparent for
purposes of showing the angled vanes 1404. In operation, an incoming wave can
approach
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the cavity at a slight angle, enter through the grate 1406 and run up each
angled vane 1404
under the grate 1406. Upon the wave run-up reaching a maximum height in the
channel
formed by the angled vane 1404, stored potential energy can then be returned
to its kinetic
form as the wave runs back down in a confined set of angled vanes 1404. The
wave then
exits the cavity through the grate with a component of azimuthal velocity
different and
largely opposite to that with which it entered. In this manner, a completely
passive
mechanism is provided for limiting or reversing azimuthal/cross-shore currents
near the
island.
[0084] In some implementations, the gutter system can provide complete or
near-
complete current reversal proximate the gutter. The importance of these vaned
cavity gutter
systems in their ability to mitigate the detrimental effects of foam-balling
on the tube of the
wave where a surfer may be riding is related to the extent to which their
effects can be
propagated away from the island. For this reason it is important that the
vanes that redirect
the flow be angled so as to inject the redirected flow into the interior of
the basin away from
the island. Typical configurations call for these vanes be angled at 45-70
degrees from the
radius around a vertical axis. The exact angle will depend somewhat on the
specific
bathimetry of the basin, but in general there is a tradeoff where more steeply
angled vanes
will perform better at redirecting the currents, and less steeply angled vanes
will better
transfer the redirected fluid to the interior of the basin, slowing the wave
at that location.
[0085] The vanes are angled both relative to a radius from the inner island
1402, as
well as to the horizontal forming a triangle to accommodate the slope of the
grating over the
vanes. FIG. 20 shows both an inside gutter system 1600 (note that in this
diagram the floor
under the grating has no apparent slope, but there may be slope in most
implementations),
and an outside gutter system 1620 between the foil 1610 and wave generation
mechanism and
the outer wall of the basin 1630. The outer gutter 1620, which is shown to
include a
horizontal plate 1640 that inhibits vertical movement of the water level from
pressure
changes when the foil moves, can be constructed in a similar way to the inner
gutter
described above. Such an outer gutter 1620 can incorporate a series of sloping
plates between
the outer wall and the perforated wall. These plates would be inclined from
the horizontal
both in the radial and azimuthal sense. In this way fluid entering the gutters
would be
redirected and exit with a velocity directed inward and counter to the
prevailing current.
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[0086] A further implementation of the flow redirection gutter system
includes
allowing the water that enters between any two vanes 1700 to run up the slope
as described
above. Upon approaching the highest point of the run-up, some of the flow is
redirected to
the adjacent gutter through a sloped opening 1720. In this way the flow is
ratcheted around
the beach further enhancing the cross shore transport. FIG. 21 illustrates
this implemented on
a sloping beach with the grating cover removed.
[0087] WAVE ABSORBING AND PHASE CANCELLATION GUTTERS
[0088] In accordance some implementations of a wave pool using an annular
basin,
both the exterior and interior boundaries of the annular basin can be fitted
with gutters and/or
baffles that are configured to limit both the reflection of any incident waves
that may be
generated by the passage of a wave generating hydrofoil, and also reduce the
persistence of
the general random chop within the basin. For example, the gutters and/or
baffles can be
configured to control particular seiching modes, or other waves of known
wavelength that are
present within the basin. As illustrated in FIG 22, some implementations of
the gutters
and/or baffles 1500 can use a perforated wall 1506, having preferably 30% -
60% open area,
and placed parallel to or inclined to, the basin's water containment walls
1504 or beaches.
The distance between the perforated wall 1506 and the main wall 1504 (b in
FIG. 22) can be
chosen so as io best. dissipate the incident or chop waves of conceit'.
[0089] In some implementations, a gutter 1500 can include a simple vertical
porous
plate of approximately 20% to 50% open area, and preferably about 33% open
area which
can form a cavity between the outer wall and the hydrofoil path. The cavity
width can be
tuned for optimal phase cancellation, as described in further detail below.
[0090] In some implementations, the gutters are provided in the basin and
are adapted
for limiting the vertical displacements and reflexted energy associated with
any trailing, or
recovery, waves generated by a moving foil or other wave generating device.
This may
involve the use of a horizontal splitter plate or step 1508 set at a height hl
that is typically
0.2h - 0.4h. In the case of a step the volume under the horizontal plate is
filled, while for a
splitter plate this volume is left open, in another variation the step
replaces the horizontal
splitter plate in the form of a vertical solid wall that extends from the
bottom up to the height
typically associated with the horizontal splitter plate. These gutters can
also be integrated
with azimuthal flow control and redirection systems, as described in the above
section.
21
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[0091] FIG. 23 illustrates a time evolution of a resulting wave from a
moving foil,
including an incident wave and reflected wave(s). The wavelength of the wave
incident on
the gutter can be L. In some implementations, it is desirable to optimize the
reflection
percentage of the resulting wave from the porous wall of the gutter, such
that, in rough
approximation:
[00921 - porous wall at a node (L/4) => 0% (*) reflection, 100% (*)
transmission.
[0093] - porous wall at a max (L/2) => 100% reflection, 0%
transmission.
[0094] If there were no perforated wall, the node may occur at a distance
of L/4 from
the back wall of the basin, and the largest energy loss may also occur at this
distance.
However, due to the inertial resistance at the porous wall, a phase change can
occur inside the
gap which can slow the waves. This makes the distance for maximum energy loss
to occur
smaller than L/4. As can be seen in FIG. 23, the width of the gutter can be
tuned based on the
size and wavelengths of incident waves that the gutter is configured to
mitigate. The gutters
can be formed of one or more parallel porous plates, and can be further
combined with a
horizontal splitter plate and/or a vertical step as described further below.
[0095] A relationship between the wavelength of the wave incident on the
gutter (L)
and that of the wave inside the gutter cavity (L1) can be such that L>L1. This
wavelength
reduction can be due to dispersion and can allow for the use of smaller width
gutters that
would otherwise be required.
[0096] Note that there can be a similar effect when a splitter plate is
used and the
condition for minimum reflection can occur at a ratio of approximately b/L,
which can be less
than a corresponding ratio for a wave chamber without the splitter plate. This
can be due to
the waves in the gutter becoming shorter over the submerged plate and hence
slowing down.
[00971 Additional implementations of a gutter 2000 are shown, for example,
in FIGS.
24 and 25, which illustrate outer gutters 2100 for an annular basin. This
outer gutter 2100
can include vertical slots 2300 in a gutter wall 2200 parallel to the main
wall 2400 to form a
porus cavity. The slotted wall could also take the form of an array of
vertical cylinders that
could have additional structural function, such as supporting a deck above the
basin. The
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porosity ratios are preferably similar to that of a similar geometry using
porous plate or
gratings, i.e. between 30-50% open area.
[0098] Note a non-perforated step 2500 that differentiates the gutter shown
in FIG. 24
from the gutter shown in FIG. 25. The step is one variant that, as with the
splitter plate, can
be combined with any of the various implementations. The step 2500 can
function in a way
similar to the splitter plate but can have the added advantage of being
structurally more
robust.
[0099] Horizontal and vertical slots or piles have different properties.
Vertical slots
or piles, when adequately spaced and sized, have a property that when the
waves impact the
vertical slots or piles obliquely, the incident and reflected paths can be
different. For
horizontally aligned piles or slots, obliqueness can have no effect and the
submersion of the
slot or pile closer to the still water level can be of importance as it can
allow smaller scale
chop or waves to enter exit the gutter area. Additionally, small variations in
the water level
can be used to adjust the relative depth of the horizontal pile or slot.
[00100] The porous walls for some gutter systems may also be integrated
with vortex-
generating roughness elements, such as described above, these can be seen on
the lower wall
of FIG. 26. As shown in FIG. 26 by way of example, some implementations can
use vertical
slots or bars 2700 to form the porous wall 2800. In addition, the slots or
bars 2700 can be
staggered such that alternative slots or bars protrude a different distances
radially from the
basin wall. In at least some instances it is not necessary that the slots or
bars alternate in their
protrusion; for example, in some implementations, every seventh or eighth slot
or bar can
protrude from a plane formed by the others. In some implementations the
protrusion distance
of the one or more slots or bars can be 8-24 inches and the distance between
the protruding
slots or bars can be 50-180 inches.
[00101] Although a few embodiments have been described in detail above,
other
modifications are possible. Other embodiments may be within the scope of the
following
claims.
23
