Analysis of radiated noise from internal duct flow and external jet using high-resolution schemes

Abstract

The modified flux approach(MFA) type finite-volume ENO schemes with a biased stencil algorithm is used to acquire their dual capacity of the high-order accuracy and non-oscillatory shock-capturing feature for computiational aeroacoustics (CAA) problems that involve the large vortices and shocks. The ENO schemes and the biased stencil algorithm is tested on shock-sound interaction problems and shown to reduce spurious oscillations in smooth regions and capture the shock very well. The transient circular pulse jets were investigated numerically for a weak $(P_4/P_1^{=8.7})$ and strong $(P_4/P_1^{=50})$ jet. After a sudden gas outflow, there are several stages in the subsequent time evolution of the underexpanded jet. It has been confirmed that the numerical results obtained by the ENO scheme for the Euler equations can successfully predict the formation process of the shock cell. In particular, the location of the first vortex as well as the shock cell with a Mach disk are remarkably well simulated quantitatively as well as qualitatively. With a simple geometric model, it is found that the major noise source of the intake stroke is the pressure surge (compression wave), which is generated after intake valve closing. The pressure surge that was converted by fluid`s kinetic energy propagates and radiates with relatively large amplitude. Some part of the pressure surge is reflected at the duct open end and the rest of it is radiated to the far field. So, its amplitude is oscillating in the duct and decays as time goes on. The unsteady deforming mesh algorithm with Lagrange interpolation is suitably applied to the periodic motion of the piston and the valve. And it enables to change the numbers of the meshes so could help simulating the motion of the perfect closing of the valve. A comparison is given between present calculated data and the measured data for in-duct pressure, which is proven to be a satisfactory result. An axisymmetric perfectly expanded superson...