Numerical Study of the Shock Tunnel Flow with a Throat Plug
In order to test the flow around a hypersonic vehicle, a shock tunnel is needed. The basic principle of a shock tunnel is well known. However, there is one part of the shock tunnel that is not known well. It is about the plug for the throat of the nozzle. Generally, a shock tunnel consists of a high pressure driver tube, a low pressure driven tube and a nozzle. Initially, driver and driven tube are separated by a main diaphragm.When the pressure difference between the two tubes is high, themetallic diaphragm should be used to maintain the initial pressure difference. When shock tunnel flow is initiated by the rupture of the main metallic diaphragm, the rupturing produces many small fragments of the diaphragm material. These diaphragm fragments move slowly toward the nozzle throat. After the useful test flow is finished, these fragments pass through the nozzle via the throat, and blast the model. This results in erosion of the model surface, damage to instrumentation and contamination of the boundary layer flow around the model, necessitating frequent model replacement. The importance of a device to avoid the flow contamination by the diaphragm fragments has been investigated since the early shock tunnel invention. Hertzberg et al.  inserted canted nozzle between two expansion nozzles which allowed the diaphragm fragments to be centrifuged out of the flow. Bird et al.  employed throat plug which is closed to terminate the nozzle flow following the useful test time and prevent upstream fragments from entering the nozzle and damaging models. However, the new development of such devices is hampered by the lack of open published data.
KeywordsNozzle Exit Hypersonic Vehicle Nozzle Throat Shock Tunnel Secondary Shock
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