Numerical Simulation Of Free Surface Turbulent Flow And Its Application

The existence and development of human has close relations with free-surface flows, the research of which has both widely practical engineering significance and important theoretic value. Due to the complication of free-surface flows, pure theoretic analysis is limited substantially and the experimental research also has many difficulties in the process of application. With the advancement of computer technique, modern numerical simulation has been greatly developed and the numerical research on free-surface flows has become one of the focuses and difficulties in hydrodynamics. In the dissertation, based on FLUENT software, the VOF(Volume of Fluid) method in combination with RNG(renormalization group) k-εmodel was used in the simulation of the motion of an ellipsoid near the free-surface, the deformation of free-surface caused by water entry and exit of the 2-D circular cylinder and the stokes waves generated by rocker-flap wave maker in a tank. The main part of the dissertation is shown as follows:In the numerical simulation of the motion of an ellipsoid near the free-surface, on the one hand, the free-surface shape and drag coefficient caused by the motion of an ellipsoid in different depth and the relationship between drag coefficient and depth were studied in detail. On the other hand, both the free-surface shape and drag coefficient caused by the motion of an ellipsoid in different Froude numbers and the relationship between drag coefficient and Froude numbers were also researched detailedly.In the numerical simulation of waves generated by rocker-flap wave maker in a tank, according to the principle of wave generation by rocker-flap, taking example for rocker-flap wave maker in Harbin Engineering University, high quality stokes wave in accuracy of second order was simulate in numerical wave tank with VOF method and dynamic mesh technique. And time series of surface elevation in different place in numerical tank, typical waves and velocity in local flow field were also researched.In the numerical simulation of water entry and exit of the 2-D circular cylinder, the free-surface deformations caused by the cylinder moving vertically upwards, vertically downwards, and obliquely downwards were investigated as well as the reasons for these deformations.The computational results showed that VOF method in combination with RNG k-εmodel was effective on the numerical simulation of free-surface flows.