| Free surface flow is a phenomenon in human being's daily life, which has great significance in both scientific research and engineering application. However, it is not easy to study free surface flow because of its complexity, there is still a long way to go before human could get the ultimate understanding to free surface flow. In the past decades, CFD (Computational Fluid Dynamic) has been proved to be an effective way of studying free surface flow and has been successfully applied in related studies.In this work, a CFD framework CIP-ZJU is proposed for the study of free suraface flow. A CIP-based algorithm is adopted to solve Navier-Stokes equations:a third-order finite differ-ence scheme CIP (Constraint Interpolation Profile) scheme is proposed for the advection term; Central difference scheme is adopted for diffusion term; Pressure Poisson equation is solved by SOR(Successive Over-Relation) method. CIP-ZJU framework contains two free surface capturing strategies:VOF (Volume of Fluid) type method (Including two high resolution VOF type methods VOF-WLIC (Volume of Fluid with Weighed Line Interface Capturing) a nd THINC/SW (Tangent Hyperbolic INterface Capturing with Slope Weighting) method) and a mass-preserved Level Set method. Meanwhile, a density-scaled balanced CSF (Continuum Surface Force) model and a two-liquid-phase VOF method are also included in CIP-ZJU framework.The CIP-ZJU framework is also applied in the study of free surface flow in this work, in-cluding dam break flow, multi-phase flow with the effect of surface force and wave-induced vortex near floating structures. In the study of dam break flow, a empirical formula for gate motion is proposed according to the experimental data, then the equation is applied to the numerical study of dam break flow. During this study, main attention is paid to the effect of gate motion to prop-agation of water front, free surface profile and the evolution of pressure on the downstream wall. The numerical study of multi-phase flow contains the drop impact on a thin water film and bubble rising problem, during these studies, the effect of surface force and the evolution of free surface are estimated. While in the study of wave-induced vortex near floating structures, vortex shedding near a surface piercing plate is observed, also the effect of the draft and width of the plate to vortex shedding is estimated.The highlights of this work includes:(1) A two-liquid-VOF method is proposed to study the inner interface between different phas-es in the same fluid within the framework of Eulerian grid system, this method has been success-fully applied in the numerical study of dam break flow with initially wet bed.(2) An improved mass-preserved Level Set method is proposed in this study, which has suc-cessfully improved the mass conservation in Level Set method.(3) An empirical formula for gate motion in dam break flow experiments is proposed from the experimental data and applied in the numerical study, which has improved the numerical result of dam break simulation.(4) The effect of gate motion in dam break flow is further studied with the application of this formula, focusing on the effect of gate motion to water front propagation, free surface evolution and impact pressure on right hand wall. The relationship between the removal speed of the gate and water front propagation is studied. |
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