Calculation of Wave Forces using REEF3D

Abstract

Non-breaking wave forces on a cylindrical pile are calculated numerically by solving the three-dimensional Navier Stokes equations in the numerical wave tank of REEF3D. Initially, the numerical wave tank is validated by comparison of the numerical results with the analytical solutions for varying grid density, time step size, numerical beach width, wave amplitude, numerical methods- time and spatial discretization, relaxation method and wave type. The performance of the wave tank under the aforementioned various conditions is observed. As a result the appropriate parameters to be used for the numerical experiment are obtained. Finally, simulations are carried out to calculate the wave forces on a cylindrical pile and the numerical results are compared to the results obtained using the Morison formula. During validation, it is observed that the wave tank gives good results with an error of 0.24% in the wave amplitude at a grid density of 100 cells per wavelength and CFL number 0.1 for a fifth order Stokes wave of amplitude 0.05m and wavelength 2m. A recent study using a different approach reported a requirement of 200 cells per wavelength. Thus, the performance of the wave tank in this study is considered very good. The calculation of wave forces also shows promising results. The wave forces from REEF3D seem to be slightly under estimated compared to the Morison force in the four numerical experiments carried out. There exists a possibility of erroneous calculation of the Morison force. There were no instabilities in the solution from the numerical calculations. Due to the absence of simple experimental data for wave force on a cylinder and time constraints, validation is attempted only through Morison formula by adding the formula in the code. The validation of wave force calculation could not be deemed conclusive.CoMEM - Coastal and Marine Engineering and ManagementHydraulic EngineeringCivil Engineering and Geoscience