Simulation of a complete reflected shock tunnel showing a vortex mechanism for flow contamination

Abstract

Abstract. Simulations of a complete reflected shock tunnel facility have been performed with the aim of providing a better understanding of the flow through these facilities. In particular, the analysis is focused on the premature contamination of the test flow with the driver gas. The axisymmetric simulations model the full geometry of the shock tunnel and incorporate an iris-based model of the primary diaphragm rupture mechanics, an ideal secondary diaphragm and account for turbulence in the shock tube boundary layer with the Baldwin-Lomax eddy viscosity model. Two operating conditions were examined: one resulting in an over-tailored mode of operation and the other resulting in approximately tailored operation. The accuracy of the simulations is assessed through comparison with experimental measurements of static pressure, pitot pressure and stagnation temperature. It is shown that the widely-accepted driver gas contamination mechanism in which driver gas 'jets' along the walls through action of the bifurcated foot of the reflected shock, does not directly transport the driver gas to the nozzle at these conditions. Instead, driver gas laden vortices are generated by the bifurcated reflected shock. These vortices prevent jetting of the driver gas along the walls and convect driver gas away from the shock tube wall and downstream into the nozzle. Additional vorticity generated by the interaction of the reflected shock and the contact surface enhances the process in the over-tailored case. However, the basic mechanism appears to operate in a similar way for both the over-tailored and the approximately tailored conditions. 2 R.

Numerical simulation of the viscous shock tube problem by using a high resolution monotonicity-preserving scheme

“…The first computations were performed by Weber et al [21] who analyzed the interaction of an isolated reflected shock wave with a laminar boundary layer; in this work, the contact discontinuity and rarefaction waves present in a shock tube were disregarded. Other numerical studies focused on the flow contamination at the end-wall of the shock tube [1,8]. The shock tube configuration at moderate Reynolds number also served as a test-case for numerical method validation [3,6,10,11,19].…”

Self-ignition of hydrogen–nitrogen mixtures during high-pressure release into air

“…Four additional simulations were performed to investigate diaphragm opening time influence, the results are presented in section 3.4. To simulate the diaphragm rupture process an Iris model [33] was used. Diaphragm with a thickness of 0.1 mm was mimicked by a cell-by-cell connection with linear rate of high-pressure and extension tube volume starting from the axis.…”

Numerical Simulation of Air-He Shock Tube Flow with Equilibrium Air Model

“…Shock bifurcation is highly related to the driver gas contamination problem occurring in shock tunnels [4,5].…”

“…By using a conical ring to capture the driver gas jet stream, the arrival time in the nozzle was increased by a factor of 2.5 in comparison with the numerical results without the wall suction. Goozée et al [5] performed a complete reflected shock tunnel simulation with an iris-based model of the primary diaphragm rupture mechanics and the Baldwin-Lomax turbulence model. Two operating conditions, over-tailored and approximate tailored conditions, were examined.…”

“…The model is a two-layer algebraic zero-equation model. It has been proved robust for high-speed flows with thin boundary layers [5].…”