A numerical study of nozzle boundary layer thickness on axisymmetric supersonic jet screech tones

In this paper, a computational aeroacoustic approach is applied to investigate the influence of nozzle boundary layer thickness on axisymmetric supersonic jet screech tones. The axisymmetric Navier-Stokes equations and the two equations standard k - ε turbulence model are solved in the generalized curvilinear coordinate system. A generalized wall function is applied in the nozzle near wall region. The dispersion-relation-preserving scheme and a high order upwind scheme are applied for space discretization in the free jet and nozzle internal region respectively. The 2N storage low-dissipation and low-dispersion Runge-Kutta scheme is employed for time integration. A straight nozzle is chosen for investigation with several different initial boundary layer thicknesses. It is shown that the nozzle boundary layer thickness has an important influence on the generation of supersonic jet screech tones. This implies that it would be an effective way to reduce the supersonic jet screech tones through increasing of nozzle boundary layer thickness. Further-more, a generic nozzle is simulated to show the capability of the present CAA approach for complex nozzle configurations with boundary layer effects accounted for.