Print Email Facebook Twitter Numerical modeling of wave run-up on a dike: Simulations with the VOF-model ComFLOW Title Numerical modeling of wave run-up on a dike: Simulations with the VOF-model ComFLOW Author Van den Bosch, I.C. Contributor Uijttewaal, W.S.J. (mentor) Labeur, R.J. (mentor) Verhagen, H.J. (mentor) Van Gent, M.R.A. (mentor) Wenneker, I. (mentor) Faculty Civil Engineering and Geosciences Department Hydraulic Engineering Programme Environmental Fluid Dynamics Date 2010-12-15 Abstract Wave fields in the close vicinity of a coastal structure can be very complex, this is especially the case during extreme storm conditions and for complex geometries. There is a growing interest for numerical simulation tools capable of predicting in detail the complex hydrodynamic loads due to waves and currents and its effect at structures. In this context the model ComFLOW will be used in this thesis to study wave run-up on dikes. The code is a (3D) hydrodynamic flow model based on the incompressible Navier-Stokes equations. The evolution of the free water surface is described by the Volume-of-Fluid method (VOF). The model is capable of calculating velocities, pressures and water levels in a detailed level, while geometries are easily adjustable. The objective of this study is to analyze numerical simulation of wave run-up and other relevant wave-structure interaction processes on smooth and impermeable coastal structures with perpendicular wave attack and to investigate whether the Volume of Fluid (VOF) model ComFLOW is able to accurately represent these processes with 2DV simulations. A related aim is to determine whether the model is robust and which model settings are preferred. To investigate whether the numerical model different mathematical aspects properly solves for relevant processes, simulation results are compared with analytical solutions. Three test cases are considered: the classical dam break test with a horizontal bed, the dam break test with an upward sloping bed and solution of Carrier and Greenspan of a non-braking, standing wave on a sloping beach. General performance of the model for the analytical solutions is well and led to the following observation: numerical diffusion can lead to a decrease of run-up and run-down heights. Numerical dissipation factors that are indicate as influential on the results: the discretization of the geometry, the algorithm of flooding of dry cells, artificial viscosity. An analysis of the different wave-structure interaction processes is performed, by studying not only wave run-up, but also wave run-down, reflection and visual inspection of the type of wave breaking. Simulations are performed with regular waves, three different slopes are used (of 1:3, 1:4 and 1:6). In combination with seven different wave conditions, this gives a wide range of breaker parameters. The results are compared with data from experimental model tests of Schuttrumpf and Bruun and Gunbak. The results with respect to wave run-up are convincing, having very good resemblance with data of physical experiments, especially for breaking waves. Nevertheless, for non-breaking waves, the computed wave run-up values are in the lower regions of the experimental data. For these waves, the (relative) numerical dissipation is too high during structure-wave interaction. The numerical dissipation due to the discretization of the geometry is indicated as the main cause of the lower wave run-up heights as compared with experimental data. The results concerning wave run-down are less convincing than the run-up results. The relative wave run-down is overestimated (hence the lowest water level reached in the simulations is lower than in the experiments) compared to experimental data, especially in the region of breaking waves. No clear explanation is found for the lower values. The answer may lay in the different physical characteristics of wave run-up and run-down or the difference in handling of flooding and drying of cells by the numerical model. The calculated reflection coefficients show good resemblance with data from physical experiments, showing that the right amount of wave energy is reflected at the structure. Overall it can be stated that the model is well able to accurately represent different wave-interaction processes including wave run-up and the model proved to be robust for this type of simulations. Subject ComFLOWVOF-modelRun-upRun-downNumerical modelingwave-structure interaction To reference this document use: http://resolver.tudelft.nl/uuid:17f019d4-ed5a-4b7e-8603-84409b1a48cd Part of collection Student theses Document type master thesis Rights (c) 2010 Van den Bosch, I.C. Files PDF Finalreport_ICvandenBosch_2010.pdf 8.37 MB Close viewer /islandora/object/uuid:17f019d4-ed5a-4b7e-8603-84409b1a48cd/datastream/OBJ/view