A Novel Method for Generating Continuously Surfable Waves—Comparison of Predictions With Experimental Results

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  
Keyword(s):  
Water Channel ◽  
Breaking Waves ◽  
Experimental Results ◽  
Stationary Waves ◽  
Ocean Engineering ◽  
Pressure Source ◽  
Circulating Water ◽  
Novel Method ◽  
The University ◽  
The Waves

In this paper, a novel idea to produce continuous breaking waves is discussed, whereby a pressure source is rotated within an annular wave pool, with the inner ring of the annulus having a sloping bathymetry to induce wave breaking. In order to refine the technique, work is being conducted to better understand the mechanics of surfable waves generated by moving pressure sources in restricted water. The pool aims to be capable of creating waves suitable for surfers from beginner to expert level, with an added benefit being by providing a safe learning environment, the overall surfing ability of the participants should be improved. The method of approach reported in this paper is the first stage of an experimental investigation of a novel method for generating continuously surfable waves utilizing a moving pressure source. The aim was to measure and assess the waves generated by two parabolic pressure sources and a wedge-shaped wavedozer (Driscoll, A., and Renilson, M. R., 1980, The Wavedozer. A System of Generating Stationary Waves in a Circulating Water Channel, University of Glasgow, Naval Architecture and Ocean Engineering, Glasgow, UK) for their suitability for future development of continuous breaking surfable waves. The tests were conducted at the University of Tasmania (UTas) Australian Maritime College (AMC) 100 m long towing tank. The predictions and experimental results for the wave height (H) at different values of depth Froude number (Frh) are presented in this paper. Finally, the preferred pressure source is determined based on the wave making energy efficiency and the quality of the waves for surfing.

A Novel Method for Generating Continuously Surfable Waves: Comparison of Predictions With Experimental Results

2011 ◽  
Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Experimental Investigation ◽  
Wave Breaking ◽  
Breaking Waves ◽  
Experimental Results ◽  
Pressure Source ◽  
Towing Tank ◽  
Novel Method ◽  
The Waves

In this paper, a novel idea to produce continuous breaking waves is discussed, whereby a pressure source is rotated within an annular wave pool. The concept is that the inner ring of the annulus has a sloping bathymetry to induce wave breaking from the wake of the pressure source. In order to refine the technique, work is being conducted to better understand the mechanics of surfable waves generated by moving pressure sources in restricted water. This paper reports on the first stage of an experimental investigation of a novel method for generating continuously surfable waves utilising a moving pressure source. The aim was to measure and assess the waves generated by two parabolic pressure sources and a wavedozer [1] for their suitability for future development of continuous breaking surfable waves. The tests were conducted at the Australian Maritime College (AMC), University of Tasmania (UTas) 100 metre long towing tank. The experimental results as variations in wave height (H) divided by water depth (h) as functions of depth Froude number (Frh) and h, together with predictions from both methods, are presented in this paper. Finally, measures of the wave making energy efficiency of each pressure source, and the surfable quality of the waves generated by it, were developed and are presented.

scholarly journals KNSwing—On the Mooring Loads of a Ship-Like Wave Energy Converter

2019 ◽  
Vol 7 (2) ◽  
pp. 29
Author(s):  
Kim Nielsen ◽  
Jonas Thomsen
Keyword(s):  
Numerical Model ◽  
Wave Energy ◽  
Numerical Models ◽  
Breaking Waves ◽  
Wave Energy Converter ◽  
Experimental Results ◽  
Irregular Waves ◽  
Mooring System ◽  
Energy Converter ◽  
The Waves

The critical function of keeping a floating Wave Energy Converter in position is done by a mooring system. Several WECs have been lost due to failed moorings, indicating that extreme loads, reliability and durability are very important aspects. An understanding of the interaction between the WEC’s motion in large waves and the maximum mooring loads can be gained by investigating the system at model scale supported by numerical models. This paper describes the testing of a novel attenuator WEC design called KNSwing. It is shaped like a ship facing the waves with its bow, which results in low mooring loads and small motions in most wave conditions when the structure is longer than the waves. The concept is tested using an experimental model at scale 1:80 in regular and irregular waves, moored using rubber bands to simulate synthetic moorings. The experimental results are compared to numerical simulations done using the OrcaFlex software. The experimental results show that the WEC and the mooring system survives well, even under extreme and breaking waves. The numerical model coefficient concerning the nonlinear drag term for the surge motion is validated using decay tests. The numerical results compare well to the experiments and, thereby, the numerical model can be further used to optimize the mooring system.

A Novel Method for Generating Continuously Surfable Waves

2010 ◽  
Vol 44 (2) ◽  
pp. 7-12 ◽  
Author(s):  
Steven Schmied ◽  
Jonathan Binns ◽  
Martin Renilson ◽  
Giles Thomas ◽  
Gregor Macfarlane ◽  
...  
Keyword(s):  
Steady State ◽  
Wave Breaking ◽  
Numerical Study ◽  
River Estuary ◽  
Breaking Waves ◽  
Scale Model ◽  
Wave Mechanics ◽  
Pressure Source ◽  
Novel Method ◽  
Future Work

AbstractThis paper presents the background and initial investigation of a novel method for generating continuously surfable waves utilizing a moving pressure source. The idea is to produce continuous breaking waves using a pressure source that is rotated within an annular wave pool. The inner ring of the annulus has a sloping bathymetry to induce wave breaking. The underlying aim of the project is to understand the wave mechanics, to allow the creation of repeatable continuous “steady-state” waves.The immediate benefits of this scientific investigation will be realized by engineering the results into a surfing wave pool for recreational health use. The longer-term benefits will be developed through fundamental investigations of breaking waves.Preliminary experiments into creating a continuous steady-state wave were conducted in a towing tank using a series of pressure sources. The results have then been used to validate an initial numerical study. In addition, qualitative, full-scale experiments were carried out using a fishing vessel in a river estuary. This paper reports on the research conducted to date and plans for future work, including conducting experiments utilizing a 10-metre-diameter scale model.

scholarly journals Limitations on the Creation of Continuously Surfable Waves Generated by a Pressure Source Moving in a Circular Path

2013 ◽  
Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  
Keyword(s):  
Life Cycle ◽  
Wave Height ◽  
Wave Breaking ◽  
Breaking Waves ◽  
Design Parameters ◽  
Sectional Area ◽  
Pressure Source ◽  
Cross Sectional ◽  
The Waves ◽  
Limiting Values

In this paper, a novel idea to produce continuous breaking waves is discussed, whereby a pressure source is 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 a pressure source moving in a circular track 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 desired 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 needed to be able to create waves suitable for surfers from beginner to expert level, defined in terms of both the wave height and angle between the wave break point angle and the beach, known a peel angle. The primary novel outcome of the research conducted was to be able to design a pressure source that most efficiently imparted wave making energy into the water, and thus generated the largest possible waves whilst travelling at the required speed for surfing. The major finding was that the design parameters are generally in competition, and to determine a balance of limiting values, the design parameters cannot 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 at the breakpoint, wave shape and given pool radius. The limiting values for the parameters were determined experimentally, with the wave life-cycle from generation through transformation to wave breaking and dissipation used to focus the investigation. Scale model experiments were conducted in both linear and circular tracks. In addition to taking quantitative measurement of wave height and current formation, a method of qualitatively scoring the waves was developed to allow various pressure source shapes, operating conditions and bathymetries to be compared in terms of their suitability for surfing. The best quality waves were produced by a wedge-shaped wavedozer pressure source, such as the device detailed in Driscoll and Renilson [1]. Blockage, defined as the pressure source cross sectional area to channel cross-sectional area, was found to have a significant limitation on the generation of high quality waves suitable for surfing in a constrained waterway. Lateral wave decay, length and depth Froude Numbers also strongly influenced the waves during their life-cycle. Fundamentally, it was determined that only a very small range of design parameter values produce the desired high and shapely waves in the extremely constrained waterway under consideration.

The U.S. Coast Guard Academy Circulating Water Channel

1981 ◽  
Vol 18 (03) ◽  
pp. 253-263
Author(s):  
Warren Colburn ◽  
William Simpson ◽  
Vernon Phelps
Keyword(s):  
Experimental Work ◽  
Test Section ◽  
Water Channel ◽  
Maximum Velocity ◽  
Coast Guard ◽  
Ocean Engineering ◽  
Ship Hydrodynamics ◽  
Engineering Programs ◽  
Circulating Water ◽  
Development Center

In 1974 it was determined that the Marine and Ocean Engineering programs at the Coast Guard Academy were suffering from the lack of a facility to allow students to do experimental work in the area of fluid mechanics and ship hydrodynamics. A study was conducted to develop and evaluate the options, and this resulted in the design and construction of a free-surface circulating water channel (CWC) with the associated instrumentation. This CWC has a test section 2 ft deep by 4 ft wide by 12 ft long and a maximum velocity in excess of 8 ft/sec (Froude No. >1). The technique of using a vertical loop circulation with a 3-to-1 compression section prior to water entry into the test section and the use of turning vanes to inhibit separation of the flow stream have resulted in a uniform velocity profile quite suitable for the experimental work by the Academy and the Research and Development Center.

The Design Limitations of a Circular Wave Pool

2014 ◽  
Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Wave Structure ◽  
Breaking Waves ◽  
Experimental Results ◽  
Scale Model ◽  
Pressure Source ◽  
Signal Tracking ◽  
Wave Disturbances ◽  
Sloping Beach ◽  
Parameter Values

In this paper, the design of a circular wave pool that produces continuously breaking waves is discussed, whereby a pressure source is 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. A predominantly experimental approach was undertaken to determine the required design parameter values and their limitations. Scale model experimental results were previously presented at OMAE 2011 and OMAE2013. This paper presents the steps to design the pool using the empirical analysis and experimental results are presented. The effect of the pressure source and pool bathymetry on the currents formed in the pool, are also presented. Through this design process, high quality continuous breaking waves with the desired plunging shape were able to be generated. Finally, the authors are planning to use the facilities and techniques developed to investigate the complexities of predefined wave fields, including the three dimensional (3D) details of the velocity, pressure and turbulence fields beneath. Understanding these complexities within multidimensional wave patterns is the key to analysing a number of different fields, including wave resistance of ships; wave disturbances to other maritime users; bank erosion; wave signal tracking; and wave structure interaction.

Flow Characteristics of Artificial Steel Reefs

2003 ◽  
Author(s):  
Hyunkyoung Shin
Keyword(s):  
Water Channel ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Design Stage ◽  
Ocean Engineering ◽  
Navier Stokes Equation ◽  
Circulating Water ◽  
Drag Forces ◽  
Numerical Predictions ◽  
Waves And Currents

In order to develop novel types of artificial steel reefs suitable for marine environments near the Korean Peninsula, it is very important to carry out model tests in the initial design stage. In the Ocean Engineering Wide Tank (L×B×Dw = 30×20×2.5m) and the Circulating Water Channel, both of the University of Ulsan, Korea, fluid drag forces acting on models of artificial steel reefs with three different sizes were measured in waves and currents and flow characteristics were observed. The comparison between test results and numerical predictions based on the Navier-Stokes equation showed a good agreement and the verification enabled to predict numerically characteristic of flow past the reefs in the designed sea conditions.

Supersonic flow investigations with a “hydraulic analogy” water channel

1951 ◽  
Vol 2 (4) ◽  
pp. 227-253 ◽  
Author(s):  
Joseph Black ◽  
O. P. Mediratta
Keyword(s):  
Water Flow ◽  
Gas Flow ◽  
Water Channel ◽  
Discontinuous Flow ◽  
Two Dimensional Flow ◽  
Hydraulic Analogy ◽  
University Of Bristol ◽  
The University ◽  
Subsonic Gas Flow ◽  
The Waves

SummmaryThis paper describes the construction of a water channel in the University of Bristol for the investigation of the analogy between the two-dimensional flow of a gas and that of shallow water with a free surface. Both continuous and discontinuous flow were examined, with a view to determining the limitations of the analogy.Continuous “ shooting “ water flow was found to be reasonably analogous with supersonic isentropic gas flow, a static depth of about half an inch appearing to be satisfactory with this particular channel. No independent check was made of the agreement, or otherwise, between “streaming” water flow and subsonic gas flow, since the method of checking used was the measurement of the angle of the waves formed on the water surface, and such waves exist only in “ shooting” flow.

PHYSICAL INTERPRETATION OF WAVE BREAKING CRITERIA

2017 ◽  
Author(s):  
Sergey Kuznetsov ◽  
Sergey Kuznetsov ◽  
Yana Saprykina ◽  
Yana Saprykina ◽  
Boris Divinskiy ◽  
...  
Keyword(s):  
Nonlinear Wave ◽  
Wave Breaking ◽  
Second Harmonic ◽  
Vertical Axis ◽  
Breaking Waves ◽  
Wave Transformation ◽  
Spectral Structure ◽  
Similarity Parameter ◽  
Nonlinear Harmonics ◽  
The Waves

On the base of experimental data it was revealed that type of wave breaking depends on wave asymmetry against the vertical axis at wave breaking point. The asymmetry of waves is defined by spectral structure of waves: by the ratio between amplitudes of first and second nonlinear harmonics and by phase shift between them. The relative position of nonlinear harmonics is defined by a stage of nonlinear wave transformation and the direction of energy transfer between the first and second harmonics. The value of amplitude of the second nonlinear harmonic in comparing with first harmonic is significantly more in waves, breaking by spilling type, than in waves breaking by plunging type. The waves, breaking by plunging type, have the crest of second harmonic shifted forward to one of the first harmonic, so the waves have "saw-tooth" shape asymmetrical to vertical axis. In the waves, breaking by spilling type, the crests of harmonic coincides and these waves are symmetric against the vertical axis. It was found that limit height of breaking waves in empirical criteria depends on type of wave breaking, spectral peak period and a relation between wave energy of main and second nonlinear wave harmonics. It also depends on surf similarity parameter defining conditions of nonlinear wave transformations above inclined bottom.

scholarly journals Modification of Airflow Structure Due to Wave Breaking on a Submerged Topography

2021 ◽  
Author(s):  
Petter Vollestad ◽  
Atle Jensen
Keyword(s):  
Wind Wave ◽  
Separated Flow ◽  
Flow Region ◽  
Breaking Waves ◽  
Leeward Side ◽  
Geometrical Properties ◽  
Image Velocimetry ◽  
Wind Profiles ◽  
The Waves ◽  
Sheltered Area

AbstractExperimental results from a combined wind–wave tank are presented. Wind profiles and resulting wind–wave spectra are described, and an investigation of the airflow above breaking waves is presented. Monochromatic waves created by the wave maker are directed towards a submerged topography. This causes the waves to break at a predictable location, facilitating particle-image-velocimetry measurements of the airflow above steep breaking and non-breaking waves. We analyze how the breaking state modifies the airflow structure, and in particular the extent of the sheltered area on the leeward side of the waves. Results illustrate that while the geometrical properties of the waves greatly influence the airflow structure on the leeward side of the waves, the state of breaking (i.e., whether the waves are currently in a state of active breaking) is not observed to have a clear effect on the extent of the separated flow region, or on the velocity distribution within the sheltered region.

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