University of Twente Student Theses


Modelling of water wave propagation with FUNWAVE-TVD

Overmars, K. (2019) Modelling of water wave propagation with FUNWAVE-TVD.

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Abstract:Marine icing is a severe hazard for ships and structures in arctic seas. In order to predict ice depositions SINTEF is working on the SprayIce project in which the formation of sprays is modelled. In this work the possibilities of FUNWAVE-TVD for modelling large-scale wave fields, which could serve as input to the spray formation simulations, are explored. FUNWAVE-TVD numerically solves Boussinesq-type equations for the propagation of water waves. The vertical dimension is eliminated in Boussinesq-type equations by expanding the horizontal velocity around a reference level and integrating over the depth. In FUNWAVE-TVD a moving reference is incorporated. For the event of wave breaking and the dissipation of energy by wave breaking two schemes are included. The equations are rewritten to conservative form to make them suitable for the numerical schemes. The spatial scheme is a hybrid finite volume-finite difference scheme. The flux and first order derivatives are treated with a high order MUSCL-TVD scheme of which fourth and second order accurate schemes are available. Higher derivatives terms are treated with a central difference scheme. The time scheme is a third order Strong-Stability Preserving Runge-Kutta scheme with adaptive time stepping. The model is validated by simulating solitary wave collisions which are compared to experimental data obtained from literature. A head-on and an overtaking collision are simulated in which waves move in opposite direction and the same direction respectively. In both cases the results are very similar to the experimental data, but minor errors do exist. In the head-on case the simulated collision occurs faster than the experimental results and in the overtaking case the wave propagation is faster than expected. The large scale simulations show that FUNWAVE is capable of modelling these large wavefields. The nesting possibilities were also explored and demonstrate the capabilities of the code to transfer the results from a coarse grid to a finer grid. In these simulations the code is run on a computing cluster where up to 25 processors were used. Some instability problems were observed in the large scale simulations on the transition from water to land. This is attributed to the high gradients which can occur in this region and a numerical feature, the minimum water depth.
Item Type:Internship Report (Master)
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:FUNWAVE-TVD, water waves modelling, CFD, Boussinesq-type equations
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