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Limitations on the creation of continuously surfable waves generated by a pressure source moving in a circular path

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Schmied, SA (2014) Limitations on the creation of continuously surfable waves generated by a pressure source moving in a circular path. PhD thesis, University of Tasmania.

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Abstract

The aim of the research presented in this work was to investigate the novel idea to produce
continuous breaking waves, whereby a pressure source was rotated within an annular wave
pool. The concept was that the pressure source generates non-breaking waves that propagate
inward to the inner ring of the annulus, where a sloping bathymetry (beach) triggers wave
breaking. In order to refine the technique, research was conducted to better understand the
mechanics of waves generated by moving pressure sources in a constrained waterway, the
transformation of these waves as they travel across the channel and the effect of the sloping
beach on the wave quality for surfing.
The quality of the waves was defined in terms of wave height, speed and shape, with the aim
to create plunging waves, known as “barrels”, that are highly desired by surfers. Surfers also
require a long steep crestline or “wall”, to allow a full range of manoeuvres to be performed.
Finally, the pool was required to create waves suitable for surfers from beginner to expert
level.
The major finding was that the design parameters were generally in competition, and to
determine a balance of limiting values, the parameters could not be considered in isolation.
Therefore, a set of empirical relationships between the design parameters were developed to
allow the pool to be designed for a combination of desired wave height and shape in a given
pool radius.
In the early stages of the study, a pressure source operating in a very constrained waterway
with high levels of blockage, travelling in a circular track at high depth Froude numbers was
found to exhibit highly nonlinear behaviour. This behaviour appeared to invalidate the use of
linear and simpler non-linear potential flow numerical modeling tools to analysis the wave
pool design. Even considering simplified configurations (such as a linear track, no blockage and no beach), the predicted wave heights and shape generally did not correlate well with
initial experimental results.
Thus, a predominantly experimental approach was undertaken. A method of qualitative
scoring wave shape from a surfer’s perspective was developed and proved valuable for
focusing the research effort. At the end of the test series, high quality continuous breaking
waves with the desired plunging shape were able to be generated, with these waves being
desirable for surfing. However, it was determined that only a very small range of design
parameter values produced the desired high, plunging waves in the very constrained waterway
under consideration, and the wave quality was shown to be extremely sensitive to changes in
the design parameters.

Item Type: Thesis (PhD)
Keywords: Surfing, wave, pools, moving, pressure source
Copyright Holders: The Author
Copyright Information:

Copyright 2014 the author

Date Deposited: 14 Oct 2015 01:30
Last Modified: 21 Apr 2016 01:43
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