NUMERICAL STUDY ON SOUND GENERATED BY SHOCK-VORTEX INTERACTIONS
激波-涡干扰声场的数值研究

By using the direct numerical simulation, two-dimensional flows produced by the interactions between a shock and a single vortex or a pair of vortices are studied. The fully compressible Navier-Stokes equations are solved by fifth-order accurate upwind compact scheme for spatial derivatives together with the fourth-order accurate Runge-Kutta scheme for time integration. A series of time-dependent numerical simulation results are presented. The effects of the strengths of shock and vortices on the flow fields are examined. The characteristics of near-field sound generated by the interactions are underscored. The deformation of the shock structure is analyzed. Within the interaction region, pressure gradient in the direction parallel to the shock is created and then promotes the generation of secondary reflected shock. The generation of acoustic is associated with the deformation of the shock structure. For the case of a single vortex, two kinds of acoustic waves are observed: precursor and second sound. Both of them are of quadrupolar nature. The circumferential distribution of sound pressure is compared to other results. It is shown that present result from Navier-Stokes equation is in good agreement with corresponding experimental result and Euler solution. It is also found that the decay of the sound pressure is inversely proportional to r^{4/5} in the near-field. For the case of pair of vortices, the flow field and sound generated by the interactions differs significantly depending on the rotational direction of vortices.