Limitations On The Creation of Continuously Surfable Waves Generated By A Pressure Source Moving In A Circular Path

Limitations On The Creation of Continuously Surfable Waves Generated By A Pressure Source Moving In A Circular Path

Schmied, S.A.

Huijsmans, R.H.M. (promotor)

Mechanical, Maritime and Materials Engineering

Ship Hydrodynamics

2014-01-29

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.

Surfing
Wave
Pool

https://doi.org/10.4233/uuid:36c79c82-f901-4c75-910a-c61dd3d9d5e5

University of Tasmania and Delft University of Technology

2015-01-29

9781862959347

Institutional Repository

doctoral thesis

(c) 2014 Schmied, S.A.