Mechanism of Shock Wave Oscillation in Transonic Diffusers

Investigation of large scale shock movement in transonic flow

“…In accordance with the theory of Handa et al (2003) pressure waves do reach the upper boundary of the domain. They orginate however not only from the separated region but also from the relaminarization and the deflection of the flow.…”

“…One common feature in most such flows is that they are choked. This can be seen in many pictures in AGARD (1986) and in the cases reported by Handa et al (2003) and Moroianu (2003). The hypothesis that choking is necessary is supported by the work of Bachalo and Johnson (1986) who considered an unchoked axisymmetric configuration and observed that the inviscid flow on their model was "exceptionally stable".…”

“…A common approach, especially for LES, is to replace the ceiling of the channel with a symmetry plane. Handa et al (2003) made experiments and quasi one-dimensional computations of a transonic diffuser. They investigated two different maximal Mach numbers before the shock (1.26 and 1.48), and the diffuser was choked.…”

Experimental and Numerical Study of Oscillating Transonic Shock Waves in Ducts

“…Computational simulations of unsteady compressible internal flows are relatively common [2][3][4], although the vast majority of these use simplifying assumptions to reduce the complexity of a problem and make it easier to solve. For example, often a flow is assumed to be symmetrical and primarily two-dimensional (or at least quasi-twodimensional) so that only a section of the real flow is computed (e.g., half or quarter of a channel) and boundary conditions such as sidewalls are simplified by assuming they are inviscid or that the flow is periodic in the spanwise direction.…”

“…A number of experimental and numerical studies [2,3,[5][6][7][8] have implemented a variable geometry second throat to investigate the effects of downstream periodic pressure perturbations on shocks both experimentally and numerically. The authors of these studies found that the amplitude of shock motion decreased with increasing frequency (see Fig.…”