Positioning of Normal Shock in a Novel Constant-Area Test Section: A Numerical Study

What is it about?

In order to compare the performance of devices to control normal shock/boundary-layer interaction it is preferable to setup a stable normal shock in an (almost) constant area duct. This is however difficult to achieve in a conventional wind tunnel test section, and typically requires changes to flow conditions upstream of the shock to maintain the shock position with the introduction of a control device. In the recent past, an experimental setup has been developed at Cambridge University wherein a stable normal shock can be setup by just changing the angle of a choking flap downstream of the normal shock. In this work numerical simulations for positioning a normal shock in a computational domain that mimics the wind-tunnel test section developed at Cambridge university are presented. The work uses a non-conventional CFD technique, an immersed-boundary method, to model the choking flap, which makes the numerical procedure efficient. CFD results show that the shock can be positioned at the same position in the test section in the presence and absence of (flow) control surfaces by just adjusting the flap angle and does not require changes to the stagnation properties of the fluid (air) as in the experiment.

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