Numerical Simulation Study Of The Hydrodynamics Of Incompressible Fluids Under Alternate Excitation

The numerical simulation method of incompressible fluids in a two-dimensional tanks is studied in this paper.The mathematical models based on the incompressible potential flow equation and the incompressible,dissipative,viscous Navier-Stokes equations are developed and the hydrodynamic characteristics of the potential equations and Navier-Stokes equations with dissipation in a two-dimensional tanks are studied.The main works in this paper are as follows:(1)The Crank-Nicolson finite difference method for the potential flow equation is established.The variable regularity of wave elevation in the free surface for an incompressible potential fluid are simulated numerically,when the tank goes through two phases excitation motions,surge motion and free oscillation.The wave elevation on the free surface maintains resonances phenomenon in first phase surge excitation.When the wave amplitude in the free surface is small in the first phase,the wave elevation presents the characteristics of standing wave in the second stage,and the wave elevation does not decrease and the nonlinear phenomenon does not appear.When the wave amplitude in the free surface is large under the surge excitation motion,the wave elevation on the free surface decreases and appears obvious nonlinear phenomenon in the second excited stage.(2)The Crank-Nicolson finite difference method is established for the incompressible Navier-Stokes equations with a dissipative parameter and is applied to numerically simulate the regularity of the wave elevation and vortexes in the flow fields when the tanks is forced with two alternate excited motion.When the dissipative parameter is zero,the process of vortex which is concern with becoming?developing and disappearance is different from a single pitch motion vortexes when the tank first forced surge then pitch motion;Secondly,when the tank is subjected to the pitch motion then free oscillation motion,the vortex of the fluid fields disappears as the pitch motion disappears,and it is found that the flow direction of the internal fluid is inconsistent when the left wall on the free surface is at the crest(or trough);When the dissipative parameter is non-zero,the flow direction of the fluid does not change,and the time of internal change delays in the fluid when the Navier-Stokes equations with different dissipation parameter.