Brian Burke, an AAE undergraduate at the time of the work, has carried out time-accurate Reynolds-averaged Navier-Stokes calculations of inlet-isolator unstart at Mach 4.9. The calculations were anchored to a set of time-resolved inlet-isolator experiments carried out in the University of Texas at Austin Mach 5 wind tunnel. The image below shows the started, steady-state flow that provides the initial condition for the unsteady calculations. Predictions for this steady initial flow agreed well with experimental data.
To mimic the ramp used experimentally to initiate unstart, an unsteady artificial body force term was introduced in the conservation equations, localized at the duct outlet. The resulting transient simulation reproduced the sequence, structure, and transient features of unstart observed in the experiments. Unfortunately, they did not exactly replicate the timing of these events. With better calibration of the parameters that characterize the artificial ramp that initiates unstart, we expect that the artificial body force approach will become a cost-effective means of initiating unstart in simulations.
Initial work on this project was carried out by Purdue MS student Ian Hall. Computational resources for this work were provided by Purdue University’s Rosen Center for Advanced Computing, and the calculations were carried out using the open-source CFD code SU2.