Aeroacoustic tonal noise prediction of open cavity flows involving feedback

A new hydrodynamic/acoustic splitting method is employed to predict aeroacoustic tonal noise of self-sustained oscillatory flows over the open cavity at low Mach numbers. Acoustic field is computed using a sixth-order compact scheme and a fourth-order Runge-Kutta method, with acoustic sources obtained from the unsteady incompressible Navier-Stokes calculation. First, numerical accuracy of the present splitting method is assessed for the aeolian tone generated by Karman vortex shedding from a circular cylinder at Re_D = 200 and M_∞ = 0.3. A direct comparison was made with solutions of direct acoustic numerical simulation (DaNS) and Curle's acoustic analogy. The fundamental mode characteristics of the cavity flows at (i) Re_δ* = 850 and M_∞ = 0.077 and (ii) Re_δ* = 1620 and M_∞ = 0.147 are examined by the present method, verifying the solution with the experimentally measured sound pressure level (SPL) spectra. A dual tone characteristic observed in experiment (Henderson 2000) for case (i) is also confirmed computationally by the present method.