A Proposed Vertical Expansion Tunnel

Issues resulting from the rupture of the secondary diaphragm in an expansion tunnel may be mitigated by matching the test gas pressure and the accelerator gas pressure, orienting the tunnel vertically, and initially separating the test gas from the accelerator gas by density stratification. Two benefits are: 1) the removal of the diaphragm particulates in the test gas after its rupture and 2) the elimination of the wave system that is a result of a real secondary diaphragm having a finite thickness and mass. An inviscid perfect-gas analysis is performed to find the reservoir conditions available in the vertical expansion tunnel (VET) for comparison to a conventional expansion tunnel (ET) and a reflected shock tunnel (RST). A numerical inviscid perfect-gas analysis is presented to estimate the available test time in the VET. The effective reservoir conditions of the VET lie somewhere between the RST and the ET