Computational duct aeroacoustics using CE/SE method

One-step duct aeroacoustic simulation has received attention from aerospace and mechanical high-pressure fluid-moving system manufacturers for quite some time. They aim to simulate the unsteady flow and acoustic field in the duct simultaneously in order to investigate the aeroacoustic generation mechanisms. Because of the large length and energy scale disparities between the acoustic far field and the aerodynamic near field, highly accurate and high-resolution simulation scheme is required. This involves the use of high order compact finite difference and time advancement schemes in simulation. However, in this situation, large buffer zones are always needed to suppress the spurious numerical waves emanating from computational boundaries. This further increases the computational resources to yield accurate results. On the other hand, for such flow device as turbocharger, the sudden release of high pressure might results in the occurrence of propagating pressure discontinuity (shock wave) with local supersonic Mach number. Usually numerical aeroacoustic scheme that is good for low Mach number flow is not able to give satisfactory simulation results. Therefore, the aeroacoustic research community has been looking for a more efficient one-step duct aeroacoustic simulation scheme that has the comparable accuracy to the finite-difference approach with smaller buffer regions, yet is able to give accurate solutions from subsonic to low supersonic flflows. The conservation element and solution element (CE/SE) scheme is one of the possible schemes satisfying the above requirement. This paper aims to report the development of a CE/SE scheme for one-step duct aeroacoustic simulation and illustrate its robustness and effectiveness with two selected benchmark problems. One is the shock propagation at duct junctions and the trailing edge noise problem (Problem 2 in Category 4, the Fourth CAA Workshop of AIAA).