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 ◽  
...  

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.

Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  

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.


Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  

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.


Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  

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.


Author(s):  
Steven A. Schmied ◽  
Jonathan R. Binns ◽  
Martin R. Renilson ◽  
Giles A. Thomas ◽  
Gregor J. Macfarlane ◽  
...  

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.


2020 ◽  
Author(s):  
Konstantina Aikaterini Maroudi ◽  
Sebastiaan Reijmerink

<p>Wave penetration is a challenge for hydraulic engineers as it governs vessels’ sailing and mooring and regulates port operations. A complete approach to describe this phenomenon is by a physical scale model, which is time consuming and expensive. Therefore, a numerical model is a valid alternative. In this study, wave penetration is simulated with the non-hydrostatic model SWASH (Zijlema, 2011). To validate the model, part of an open benchmark dataset of physical scale model tests (Deltares, 2016) is used. This research addresses regular waves conditions and a simple harbour basin layout, in which reflection and diffraction are the main wave processes. This study assesses SWASH’s capability to model these processes, separately and in combination, in the full harbour layout.</p><p>1. Methodology</p><p>Reflection outside and inside the harbour is studied by two simplified 1D SWASH models, while diffraction inside the harbour by a simplified 2D model. The final SWASH model represents the full harbour layout. In all the models the water level time series at the output locations are compared qualitatively to the respective series measured at the wave gauges. Moreover, the measured steady state wave height is compared to the SWASH outputs. The “Difference”, Eq. (1), is computed to evaluate the model accuracy and to quantify the relative importance of each wave process.</p><p>Difference/diff.=(H<sub>SWASH,mean</sub>-H<sub>measured,mean</sub>)/H<sub>measured,mean  </sub>(1)</p><p>Where H<sub>SWASH,mean </sub>; H<sub>measured,mean </sub>: mean steady state wave height obtained by SWASH or measured respectively [m].</p><p>2. Results</p><p>Although the reflection trends are reproduced qualitatively in SWASH, the exact steady state wave height values may deviate significantly (diff.>30%). Moreover, the initial diffraction trends are also identified in SWASH despite their short duration in the measurements. Regarding the steady state wave height, diffraction influences considerably the total measured wave penetration inside the harbour. In the final SWASH model, the overall changes in the wave height are reproduced by SWASH. The agreement between the measured and the computed wave height is good at many output locations (diff.<10%). However, at some locations the accuracy is low (diff.>40%), owing to standing wave patterns which change fast within a short horizontal distance. Thus, the wave height can vary significantly at the area close to a specific wave gauge.  Finally, for relatively high waves and/or breaking waves, numerical instabilities are detected. Higher spatial resolution is required to capture such phenomena.</p><p>3. Conclusions</p><p>The study shows SWASH capability to reproduce qualitatively the most important reflection and diffraction trends. To a large extend, diffraction is the main process determining the wave height inside the harbour; reflection at the harbour end comes second. Outside the harbour, reflection off a quay wall is the dominant process, while reflection off a gravel slope is noteworthy. All in all, it is concluded that for non-breaking, relatively low waves, SWASH accuracy in modelling wave penetration is sufficient for engineering purposes. With further validation to guarantee the model stability, the implemented methodology can be a useful tool to understand the performance of SWASH in modeling wave penetration per wave process and in combination.</p>


2019 ◽  
Vol 7 (1) ◽  
pp. 43-53
Author(s):  
Abbas Jassem Jubear ◽  
Ali Hameed Abd

The heat sink with vertically rectangular interrupted fins was investigated numerically in a natural convection field, with steady-state heat transfer. A numerical study has been conducted using ANSYS Fluent software (R16.1) in order to develop a 3-D numerical model.  The dimensions of the fins are (305 mm length, 100 mm width, 17 mm height, and 9.5 mm space between fins. The number of fins used on the surface is eight. In this study, the heat input was used as follows: 20, 40, 60, 80, 100, and 120 watts. This study focused on interrupted rectangular fins with a different arrangement and angle of the fins. Results show that the addition of interruption in fins in various arrangements will improve the thermal performance of the heat sink, and through the results, a better interruption rate as an equation can be obtained.


Author(s):  
Sergey Kuznetsov ◽  
Sergey Kuznetsov ◽  
Yana Saprykina ◽  
Yana Saprykina ◽  
Boris Divinskiy ◽  
...  

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.


2019 ◽  
Vol 8 (3) ◽  
pp. 5795-5802 ◽  

The main objective of this paper is to focus on a numerical study of viscous dissipation effect on the steady state flow of MHD Williamson nanofluid. A mathematical modeled which resembles the physical flow problem has been developed. By using an appropriate transformation, we converted the system of dimensional PDEs (nonlinear) into coupled dimensionless ODEs. The numerical solution of these modeled ordinary differential equations (ODEs) is achieved by utilizing shooting technique together with Adams-Bashforth Moulton method of order four. Finally, the results of discussed for different parameters through graphs and tables.


2021 ◽  
Vol 9 (5) ◽  
pp. 520
Author(s):  
Zhenyu Liu ◽  
Zhen Guo ◽  
Yuzhe Dou ◽  
Fanyu Zeng

Most offshore wind turbines are installed in shallow water and exposed to breaking waves. Previous numerical studies focusing on breaking wave forces generally ignored the seabed permeability. In this paper, a numerical model based on Volume-Averaged Reynolds Averaged Navier–Stokes equations (VARANS) is employed to reveal the process of a solitary wave interacting with a rigid pile over a permeable slope. Through applying the Forchheimer saturated drag equation, effects of seabed permeability on fluid motions are simulated. The reliability of the present model is verified by comparisons between experimentally obtained data and the numerical results. Further, 190 cases are simulated and the effects of different parameters on breaking wave forces on the pile are studied systematically. Results indicate that over a permeable seabed, the maximum breaking wave forces can occur not only when waves break just before the pile, but also when a “secondary wave wall” slams against the pile, after wave breaking. With the initial wave height increasing, breaking wave forces will increase, but the growth can decrease as the slope angle and permeability increase. For inclined piles around the wave breaking point, the maximum breaking wave force usually occurs with an inclination angle of α = −22.5° or 0°.


Author(s):  
Adra Benhacine ◽  
Zoubir Nemouchi ◽  
Lyes Khezzar ◽  
Nabil Kharoua

A numerical study of a turbulent plane jet impinging on a convex surface and on a flat surface is presented, using the large eddy simulation approach and the Smagorinski-Lilly sub-grid-scale model. The effects of the wall curvature on the unsteady filtered, and the steady mean, parameters characterizing the dynamics of the wall jet are addressed in particular. In the free jet upstream of the impingement region, significant and fairly ordered velocity fluctuations, that are not turbulent in nature, are observed inside the potential core. Kelvin-Helmholtz instabilities in the shear layer between the jet and the surrounding air are detected in the form of wavy sheets of vorticity. Rolled up vortices are detached from these sheets in a more or less periodic manner, evolving into distorted three dimensional structures. Along the wall jet the Coanda effect causes a marked suction along the convex surface compared with the flat one. As a result, relatively important tangential velocities and a stretching of sporadic streamwise vortices are observed, leading to friction coefficient values on the curved wall higher than those on the flat wall.


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