Wave Tank Model Research Articles

Simulation of a 3D Numerical Viscous Wave Tank

A numerical scheme was developed to solve the unsteady three-dimensional (3D) Navier–Stokes equations and the fully nonlinear free surface boundary conditions for simulating a 3D numerical viscous wave tank. The finite-analytic method was used to discretize the partial differential equations, and the marker-and-cell method was extended to treat the 3D free surfaces. A piston-type wave generator was incorporated in the computational domain to generate the desired incident waves. This wave tank model was applied to simulate the generation and propagation of a solitary wave in the wave tank and the diffraction of periodic waves by a semiinfinite breakwater. The computation was carried out by a PC cluster established by connecting several personal computers. The message passing interface (MPI) parallel language and MPICH software were used to write the computer code for parallel computing. High consistency between the numerical results and the theoretical solutions for the wave and velocity profiles confirms the accuracy of the proposed wave tank model.

Numerical Wave Flume with Immersed Boundary Method and its Applicability in Wave Field Simulation around a Horizontal Circular Cylinder

In this paper, we present a new numerical wave flume model capable of handling interface problems with complex geometry on a standard regular Cartesian grid, using immersed boundary method. Force terms are incorporated to the momentum equations to represent the interface on a fixed Cartesian grid and they are calculated on a finite number of Lagrangian points distributed over structure-fluid interface. The wave field around a horizontal circular cylinder has been chosen in order to validate applicability of the proposed numerical wave tank model. The calculated wave forces acting on cylinder are compared with previous experimental and numerical results. Results show that the proposed model gives good agreement with experimental results.

A fully-spectral 3D time-domain model for second-order simulation of wavetank experiments. Part B: Validation, calibration versus experiments and sample applications

A 3D second-order numerical wavetank (NWT) model, SWEET, is presented. In the first part (A) of the paper [Bonnefoy F, Le Touzé D, Ferrant P. A fully-spectral 3d time-domain model for second-order simultion of wavetank experiments. Part A: Formulation, implementation and numerical properties. Appl Ocean Res 2005 [submitted for publication]. doi:10.1016/j.apor.2006.05.004], the fully-spectral formulation we employ has been detailed, and the numerical properties of the model analyzed. In the present part (B), careful validation by comparison to analytical and experimental results is first reported. Thanks to the efficiency of the proposed spectral method, the shortest wavelengths in the wavetank can be accounted for with moderate computational times. The consequent possibilities are illustrated here for the following 2D and 3D complex wave-pattern simulations, with experimental comparisons: wave-packet and geometric focusing cases, directional wavefields, long-time evolutions of irregular waves. The numerical model features all the physical characteristics of a wavetank (snake wavemaker, experimentally-calibrated absorbing zone, etc.). Its usefulness to help preparing and analyzing experiments is shown in relation to some key practical requirements: e.g. quality and evolution of the usable test zone and usability of enhanced wavemaker motions.

A fully-spectral 3D time-domain model for second-order simulation of wavetank experiments. Part A: Formulation, implementation and numerical properties

In this series of two parent papers, we report on the development and validation of a 3D second order numerical wave tank (NWT) model, SWEET. In the present part (A), the fully spectral time domain formulation is described in detail. Among other original aspects, the resulting scheme is based on a resolution achieved by fast Fourier transforms (FFTs) only, leading to very interesting properties in terms of computational efficiency. An extensive verification study of the model accuracy and convergence properties is reported in the context of both local and global quantities. The efficiency and fast-convergence offered by the proposed spectral method allow one to accurately account for the shortest wavelengths in the wavetank, while keeping computational times within affordable limits. The practical capabilities of the model are reported in length in the parent paper [Bonnefoy F, Le Touzé D, Ferrant P. A fully-spectral 3d time-domain model for second-order simulation of wavetank experiments. Part B: Validation, calibration versus experiments and sample applications. Appl Ocean Res 2005 [submitted for publication]], in which various 2D and 3D complex wave system simulations are compared with experiments and detailed analysis, examples given of the use of SWEET in assisting the design of experiments in a physical wavetank, and more validation results provided.

フレア護岸の設計，製作，施工

Flaring shaped Seawall was adopted as the Osako port in Kurahashi-cho for the first time in the country in consideration of low height, scene nature, preservation of sands, and economical efficiency, etc. The height of flaring shaped seawall was decided to be +6.0m using the wave overtopping rate presumption diagram ofit. Although we conducted the two-dimensional wave tank model in the proposal section and the wave overtopping rate (0.0002m3/m/s) checked that it was1/50 of the permissible value, the breaking wave pressure became large shockingly, it was about five times the Goda equation wave pressure. Structure of flaringshaped seawall was made into the composite construction of steel and concrete. The structure design was performed in finite-element analysis by making this shockingly breaking wave load into static load and was able to be designed rationally. Since composite structure was adopted, construction of flaring shaped seawallwas able to be performed very easily.

A numerical wave tank model for cavitating hydrofoils

In this paper, an iterative boundary element method (IBEM) for both 2-D and 3-D cavitating hydrofoils moving steadily inside a numerical wave tank (NWT) is presented and some extensive numerical results are given. The cavitating hydrofoil part, the free surface part and the wall parts of NWT are solved separately, with the effects of one on the others being accounted for in an iterative manner. The cavitating hydrofoil surface, the free surface, the bottom surface and the side walls are modelled by a low-order potential based panel method using constant strength dipole and source panels. Second-order correction on the free surface in 2-D are included into the calculations by the method of small perturbation expansion both for potential and for wave elevation. The source strengths on the free surface are expressed in terms of perturbation potential by applying first-order (linearized) and second-order free surface conditions. The IBEM is applied to a 2-D (NACA16006 and NACA0012) and a 3-D rectangular cavitating hydrofoil and the effect of number of iterations, the effect of the depth of the hydrofoil from finite bottom and the effect of the walls of NWT, on the results are discussed.

STUDY ON EVALUATION OF WAVE FORCES ACTING ON WIND POWER STATION INSTALLED ON COMPOSITE BREAKWATER

This paper investigates the applicability of a few methods to evaluate wave forcesacting on a tower of wind power station installed on a composite breakwater. One method adopted here is toestimate that as the drag force, useing both velocity and elevation of overtopping waves calculated by Sugawara et.al.(1992). A comparison of wave forces by this method with physical model shows that the accuracy depends on the relative position between the tower and the horizontal surface hit by overtopping waves. It can indicate suitablepositions for installing a tower. Furthermore, Goda's experimental formula is applied for a test as well as a numerical wavetank model with VOF function.

Exxon Valdez Oil Weathering Fate and Behavior: Model Predictions and Field Observations1

ABSTRACT Outdoor flow-through seawater wave tank studies and model predictions on the chemical and physical fate of Prudhoe Bay crude oil in subarctic waters are compared with field observations from the Exxon Valdez oil spill in Prince William Sound, Alaska. Excellent agreement is obtained between predicted and observed parameters, including evaporative loss of lighter distillate cuts, water content in mousse, density, viscosity, oil/water and oil/air interfacial surface tension, and chemical composition. As predicted from wave tank studies, water column samples of dispersed and dissolved oil and suspended particulate material collected from several heavily oiled sheltered coves and bays in Prince William Sound indicate that little oil reached the near-shore benthic environment during the first few weeks after the spill.

The Influence of Headland Alignment on the Plan Shape of Modelled Zeta‐Form Beaches

The east coast of Australia includes many beaches exhibiting a zeta‐form or log spiral curve when viewed in plan. It has already been established that there is a relationship between the orientation of such beaches and their curvature. This paper extends understanding by examining the relationship of the upswell headland and the curvature of model beaches. A wave tank model simulates the variation in beach orientation relative to wave approach direction and examines the response in beach curvature to changes in headland alignment.

WAVE-INDUCED EFFECTS IN A COOLING WATER BASIN

Wave-induced effects have been observed in a model of the cooling water intake basin of the Pacific Gas and Electric Company's Diablo Canyon Nuclear Power Plant. This model, built to an undistorted scale of 1:45, was constructed initially to study the design for the repair of the terminus region of the West breakwater damaged in storms of January 28, 1981. It was decided by PG&E to investigate, in the same model, the forces due to waves acting on two air intake structures for the auxiliary saltwater pumps and the pressures or. the external and the internal walls and the ceiling of the cooling water intake structure located in the manmade cooling water intake basin. During the course of the experiments it was noticed that the mean water level in the breakwater enclosed basin changed as a function of the incident wave characteristics. This allowed waves to overtop the cooling water intake structure which, without the change in mean water level, would not have occurred. It is this difference between the mean water level and the still water level inside the cooling water basin, defined as ponding, which will be reported herein. Diskin, et al. (1970) investigated this effect behind low and submerged permeable breakwaters in a two-dimensional wave tank model. As was mentioned by them, in normal breakwater tests it is a common practice to provide some means of communication between the seaward and shoreward side of the breakwater so that precisely this mean water level change due to overtopping of the structure does not occur. For their experiments the change in mean level varied from about 5% of the deep water wave height to 32% of the deep water wave height depending upon the submergence of the breakwater crest; the smallest change corresponded to the largest depth over the breakwater crest. This effect was discussed by Dalrymple and Dean (1971), and they proposed an analytical model based on the conservation of mass. The estimated inflow was equated to an estimate of the return flow over and through the permeable structure. Some limited agreement with the results of Diskin, et al. (1970) were shown.

Random dynamic analysis of an offshore single anchor leg storage system

A linearised spectral analysis is presented for the surge motion of a 240000 t tanker in head seas and the pivot and riser forces in the mooring system. The theoretical results are found to compare favourably with those obtained from wave tank model tests, demonstrating the applicability of linearised spectral techniques in evaluating the combined high/low frequency response of moored systems.

Dynamic Responses of Floating Structures

Theoretical and experimental studies were conducted to investigate wave loadings on, and structural responses of, floating platforms. Strip theory is applied to calculate wave forces on the structure. The wave forces, the interaction between waves and the structure, and the resulting inertia forces are then applied to the structure, as external forces, to calculate member stresses. The structure is treated as a space frame for stress calculations. Typical characteristics of dynamic stresses resulting from wave loading are considered. A wave tank model test program was conducted to collect strain data. The model test program, measurements, and correlation of measured data with theoretical calculations are considered. Satisfactory agreement was found between theoretical stress calculation and measured data.