Pool design

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In order to get the best results with the Wave Ball, the pool design must satisfy several conditions in terms of shape, depth, freeboards, filtration and accessories. Some of those conditions have an impact on a project since its very beginning; this is why it is important to take advice from WOW Company since the first step of a new project. The goal in the pool design will be the quest for the best resonance.

 

Freeboards

Freeboards are necessary to contain the waves and for the resonance.

 

The freeboards have to be flat and coplanar with the walls of the tank (pics 1 and 2). The freeboard height will be the element that will determinate the maximum height of the wave.

Fig 1: Wave amplitude repartition
Fig 1: Wave amplitude repartition

 

The wave height is distributed as follow (fig 1): 1/3 under the nominal water level and 2/3 above.

The maximum wave height is given by the formula: Max wave height = 1.5 x the height of the freeboard.

For example, most of the Rescue & Survival Training Centers need a wave of one meter; therefore, the height of the freeboard needed is 100/1.5 = 66cm.

 

 
Pic 1: pool with perfect flat freeboards
Pic 1: Tank with perfect flat freeboards
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Pic 2: pool with perfect flat freeboards
 

Filtration

In combination with the freeboards, the filtration has to have a minimal impact on the flatness of the freeboard. The figures here below (fig 2) represent the most common combinations of freeboards with filtrations. Following the configuration it is good or not for the wave formation.

 
Fig 2: Filtration configurations
Fig 2 : Filtration configurations
 
 

Skimmers

The best filtration system for Rescue & Survival Training Centre that keep a good resonance are the skimmers. In a general way, the less skimmers there are, the better it is for the resonance (pic 3).

 

 
Pic 3: pool with skimmer filtration
Pic 3: Tank with skimmer filtration
 
 

Channel filtration (Wiesbaden…)

This is the worst filtration system for the resonance, as it breaks the flatness of the freeboard. Several solutions exist in order to reduce the loss of resonance they produce.

  • A: The channel filtration is divided in several channels of smaller lengths. Those lengths should be about 1.5m long and placed along the perimeter of the pool where the impact on the resonance will be minimum. That placement has to be done following the computer simulation results in order to be placed at nodal points or lines.
  • B: The filtration channel is covered by stainless steel plate or other material (pics 4 and 5). This stainless steel plate has 2 or 3 rows of maximum Ø8mm holes or a 5mm wide gap line for the filtration on its length. This is the best covering method as it lets the water passing for the filtration while keeping the resonance. The place and total length of such a covered filtration channel is not important as it does not have “any” impact on the resonance.
 
Pics 4: 8mm holes for filtration
Pics 4: 8mm holes for filtration
Pics 5: Covered filtration with 5mm gap line
Pic 2: pool with perfect flat freeboards
 

 

Overflow filtration

Overflow filtration is not compatible with the Wave Ball as this kind of filtration is generally done in order to have a tank without freeboard.

However, freeboard and overflow filtration can be combined in a nice and efficient result.

 

 
Pic 6: filtration trough freeboard
Pic 6: filtration trough freeboard
Pic 7: filtration trough freeboard
Pic 7: filtration trough freeboard
 

 

The concept is to add freeboards in front of the filtration and to let a 5mm gap at overflow level in order to let the water passing to the channels (pics 6 and 7). Those walls can be made of concrete or Plexiglas and have to be built exactly in the continuation of the wall of  the pool.

 

If the pool has a double public / rescue purpose, the pool can be equipped with removable freeboards (pic 8). During rescue time, the freeboards are installed in order to make waves and during the public time the freeboards are removed. Those removable freeboards are equipped with a filtration gap of 5mm that allow the overflow filtration even when placed.

 

Those freeboards have to be rigid and strongly anchored in the ground; any movement due to a loss of rigidity or wrong anchoring would drastically affect the resonance and reduce the amplitude of the wave.

 
Pic 8: removable freeboards
Pic 8: removable freeboards
 

 

Depth profile

General

The general rule is that the depth of the tank has to be at least 2 times the maximum amplitude of the waves (fig 3). For example, if the maximum height of waves is 0.75m; the shallow area should be at least 1.5m for an optimum resonance. If waves of 1m high are required, shallow area of  1.5m depth is still accepted. However, we recommend that part of the pool to be as small as possible.

Platforms and steps

Those elements should be deeper than two times the maximum amplitude. However, for maximum waves of more than 0.75m, a depth of 1.5m is still accepted. Again, the steps have to be the thinnest as possible, and the platform area the smallest as possible.

Minimum depth for the Wave Ball

Each Wave Ball model requires a specific minimal depth at Wave Ball location to be able to work.

Those minimal depth are as follow:

  • W105FL: 1.1m / 3.6”
  • W105F: 1.4m / 4.59 “
  • W130FL: 1.25m / 4.10 “
  • W130F: 1.5m / 4.92”
  • W150FL: 1.4m / 4.59”
  • W150F: 1.6m / 5.25”
  • W165FL: 1.5m / 4.92”
  • W165F: 1.7m / 5.58”
  • W180F: 1.8m / 5.9”
Fig 3: depth profile
Fig 3: depth profile

Those minimal depths have to be respected in a radius of 3 meters around the anchor position.

While designing the pool or while choosing the place where the Wave Ball will be anchored these positions have to be taken in account.

Handrails

Handrails are elements that reduce the resonance a lot! The handrails will start to reduce the resonance when the waves hit them. So, the higher above nominal water level they are placed, the better it is for the wave formation. In addition to that, here below are some ways that can reduce the loss of resonance if handrails are really needed.

  • Handrails can be made of a single rope ( pic 9). This is the best solution to keep the resonance.
  • The total handrail length can be reduced and placed only in some parts of the perimeter; ideally following the results of the computer simulation.
  • The handrails are placed high above water level (pic 10)

 

 
Pic 9: handrails made of ropes
Pic 9: handrails made of ropes
Pic 10: handrails above water level
Pic 10: handrails above water level