This paper reports a numerical study of a two-dimensional time-dependent viscous flow past a rectangular bluff body with a Reynolds number Re = 6 073 based on bluff body height installed in a flow duct. The leading edge of the bluff body takes a semi-circular profile. The governing equations of the flow are solved with large-eddy simulation (LES) using a commercial computational fluid dynamics software FLUENT. The focus of the present study is to explore the effects of the ratio of the height of the bluff body H and the separation D between the bluff body and the duct wall surface. The numerical simulations are validated with the results obtained from a separate wind-tunnel experiment. Numerical simulations with various D/H are carried out. The numerical results show that the mean and instantaneous flow quantities are strongly dependent on the ratio D/H. The suppression effects of vortex shedding by the neighboring duct wall are highlighted by comparing the unsteady flow structure topology, dominant Strouhal number, lift and drag forces, etc. The mechanism for the suppression of vortex shedding suppression and its variation with D/H are analyzed, and its relevance to generation of flow inducing noise by a bluff body in a flow duct is discussed.

Recent research was carried out to calculate the acoustics generation induced by flow numerically. In this paper, a modified hybrid acoustics/viscous splitting technique was employed in a computational simulation to calculate the acoustic generation when flow passes through a baffle in duct. The acoustics/viscous splitting technique for Computational Aeroacoustics (CAA) was first developed by Hardin and Pope. Traditionally, CAA problems were computed by Direct Numerical Simulation (DNS) to solve the compressible Navier-Stokes equation. However DNS is very expensive in terms of computation power and time consuming. The Hybrid approach is regarded as a alternative of solving the aeroacoustics problem. Perturbation technique is employed to calculate the acoustics perturbation which superimposes with the incompressible solution to obtain the compressible flow solution. In this paper, the hybrid CAA technique was developed and applied in a 2D duct with single baffle.

Abstract. In order to investigate the characteristics of planar free jet flows, the Monotonically Integrated Large Eddy Simulation (MILES) method with the high-resolution space-time conservation element/solution element (CE/SE) scheme was used to simulate the two-dimensional free jet flows. For free jet flows within the Reynolds number range 35300~2200, the flow structures, averaged and instant velocity, turbulence intensity, velocity profiles of different cross-sections were examined respectively. The simulation results agree well with the experiment data. A region of constant height exists right after the jet outlet, in which the average centerline velocity and turbulence intensity maintains same with the jet outlet, and the instant fluctuation amplitudes are also small. For turbulent flows, the length of the undisturbed region is equal to the length of region of constant height. While near the laminar region, the length of undisturbed region is slightly larger than the length of zone of constant height. The vortex structures start to generate after the undisturbed region, develop coherently in the region of flow establishment, and break down gradually in the region of fully established flow region. As the Reynolds number increases, the length of zone of constant height, the length of undisturbed region and the length of potential core region all decrease correspondingly.