Effects of Inflow Mach Number and Step Height on Supersonic Flows over a Backward-Facing Step

Abstract

The backward-facing step is practically implicated in many devices, encountering the massive separation flows. In the present study, simulations of supersonic flow over a backward-facing step have been carried out employing both RANS and LES. The simulated results are validated against the experimental data. The results of RANS and LES show a good comparison with the experimental results. Different inflow Mach numbers and expansion ratios are also investigated. The reattachment length decreases with the increase of inflow Mach number. The duct height has a great effect on the flow patterns. The present conclusions are helpful to understand the physics in supersonic separation flows and also provide theory basis for engineering applications.

Compressibility effects on energy exchange mechanisms in a spatially developing plane free shear layer

“…The figure reveals that the centre of the shear layer extends further into the low-speed side as the convective Mach number increases (see figure 15b). This finding may help to explain the phenomenon in the backward-facing step (known as BFS) flow, where the reattachment length decreases as the inflow Mach number increases (Chen et al 2012;Liu et al 2013). This shifting of the mean velocity profile in the FSL has been reported in previous studies, both experimental and numerical (Elliott & Samimy 1990;Goebel & Dutton 1991;Fu & Li 2006).…”

“…2012; Liu et al. 2013). This shifting of the mean velocity profile in the FSL has been reported in previous studies, both experimental and numerical (Elliott & Samimy 1990; Goebel & Dutton 1991; Fu & Li 2006).…”

Dynamics of a supersonic transitional flow over a backward-facing step

“…Compression waves are generated around the reattachment location, which coalesce into a reattachment shock (white solid line). The low-speed recirculating flow forms a separation bubble underneath the dividing line (here defined for convenience as the isoline of u = 0 indicated by black dashed line), while the high-speed part proceeds downstream by overcoming the slight pressure rise [28]. The mean reattachment length is about L r = 10.9δ 0 (3.6h), which is consistent with the existing results, reporting that the reattachment length is usually within 3.0 ∼ 4.0h around the current Mach number [28,29].…”

Numerical simulations of transverse liquid jet to a supersonic crossflow using a pure two-fluid model

“…The scope of this article is to construct a well-posed equation system for the droplet governing equations based on the kinetic theory and carry out the numerical simulation of transverse liquid jet to a supersonic crossflow. For turbulence modeling of the two phases, the k-e model was applied to the gas phase with compressible correction, 28 while the one-equation k p model was used to describe the turbulence in droplet phase. 24 Characteristics analysis was employed to investigate the well-posedness of the governing equation system, and the hyperbolic nature based on the kinetic theory was then demonstrated.…”