A numerical investigation of the noise radiated by a turbulent flow over a cavity

Description/Abstract

The tonal noise radiated by a two-dimensional cavity submerged in a low-speed turbulent flow has been investigated computationally using a hybrid scheme that couples numerical flow computations with an implementation of the Ffowcs Williams–Hawkings equation. The turbulent near field is computed by solving the short-time-averaged, thin-layer approximation of the Navier–Stokes equations, with turbulence modelled by the Wilcox k–ω model. Second order spatial and temporal discretization schemes with fine grids in the immediate region of the cavity and a small time step were used to capture the unsteady flow physics. Along all external boundaries, a buffer zone is implemented to absorb propagating disturbances and prevent spurious numerical reflections. Comparisons with experimental data demonstrate good agreement in both the frequency and amplitude of the oscillations within the cavity. The unsteady characteristics of the cavity flow are discussed, together with the mechanisms for cavity noise generation. The influence of freestream flow velocity and boundary layer thickness on the frequency and amplitude of the oscillations within the cavity and the nature of the noise radiated to the far field are also investigated. Results indicate that both the frequency and amplitude of oscillation are sensitively dependent on the characteristics of the shear layer spanning the mouth of the cavity.