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Description
Shock tube flows can be used to investigate non-equilibrium thermochemistry and radiative processes found in hypersonic flows, commonly through spectroscopy techniques which can be used to infer energy levels and number densities. The flow in a shock tube contains many flow non-uniformities, in particular boundary layer effects. For the purpose of studying the properties of the test slug, the shock itself is usually considered planar. In reality, the growth of the boundary layer produces a curved shock front. Therefore any comparison to a one-dimensional flow simulation, such as a stagnation line solution, to experimental data must account for this physical phenomenon. This work develops a method to approximately account for the influence of shock curvature on observed radiance through use of an analytical shock structure formula and subsequently to numerical data via a convolution function. This is applied to a stagnation line simulation of an air test completed in Oxford’s T6 Shock Tube, and a low pressure Titan entry condition. Over 10% change in peak radiance is observed, in addition to changing the spatial profile of the non-equilibrium radiance. This methodology provides a method to correct for the curvature effects previously ignored but which can have a significant influence on peak radiance, particularly for lower pressure test cases.
Summary
A novel method is developed and applied to account for shock curvature effects in 1-dimensional shock tube simulations.
