NUMERICAL SIMULATION AND PHYSICAL ANALYSIS OF A PRESSURE WAVE PROPAGATING IN A DUCT

摘要

This paper reports a theoretical-numerical study of the coupling between the shearing process and compressing /expanding process in fluid motion. The flow field induced by the pressure wave at the duct inlet is numerically simulated based on 2-D unsteady compressible Navier-Stokes equations with a 6th-order compact finite-difference scheme for nonlinear first derivative and third -order Runge-Kutta method for time discretization. Based on some reasonable simplifications,analytical solutions for all variables are obtained for the uniform duct and inlet pressure wave with small amplitude, numerical results agree well with the analytical solutions. When the duct has the uncontinuous change of sectional area, such as an orifice plate, strong nonlinear interactions between the pressure wave,vortices and boundary conditions make the flow field more complicated. The flow is numerically simulated and its characteristics are illustimated. Vortex shedding and synthetic jet can occur when the amplitude and frequency of the pressure wave and the opening size of the orifice meet a formation criterion, which is presented and evaluated here.