# [How to obtain supersonic flow inside a supersonic wind tunnel ?]

 Register Blogs Members List Search Today's Posts Mark Forums Read

 July 2, 2014, 14:45 [How to obtain supersonic flow inside a supersonic wind tunnel ?] #1 New Member   YU XIA Join Date: Jul 2014 Posts: 1 Rep Power: 0 Sponsored Links Hi, My name is Steven, I am a undergraduate student doing a computational project using starccm+. My model is a blow-down supersonic wind tunnel which has an inlet and an outlet. The total length of this tunnel is 5.5 m, including an inlet, a settling chamber, a convergent-divergent nozzle, an 1 m long working section, and finally a 2.5 m long diffuser. Firstly I ignored the settling chamber and modeled this wind tunnel from the nozzle to diffuser in order to fasten the computation. So I defined the beginning plane of nozzle as the inlet and the exit of diffuser as the outlet. And the inlet is 'Stagnation Inlet', whose supersonic static pressure is 102300 pa, total pressure is 184140 Pa. The outlet is 'pressure outlet', which is 102300 Pa. Then after running the computation, I can get the supersonic flow in the working section and a normal shock wave at the end of working section, which is also the inlet of diffuser. Now I tried to add the settling chamber in front of the nozzle and move the inlet to the beginning of settling chamber. Then I run the computation with the identical boundary conditions and the parameters, however I could only obtain the subsonic flow over the entire wind tunnel. I have tried to increase the inlet static pressure and total pressure or decrease the outlet pressure, but I still could only obtain the supersonic flow at the first hundreds of iterations, then when the residual started to converge, the flow drops to entirely subsonic again. Could you please tell me how to obtain supersonic flow inside this extended wind tunnel geometry? Thank you very much!!! Best regards, Steven PS: Firstly I thought it is a 'wind tunnel starting' problem, so I increased the inlet total pressure to as high as 300000 Pa, but still obtained the entire subsonic flow in the wind tunnel, so I believe it should be a numerical problem of Starccm+, because I further tried different 3D mesh types (e.g. polyhedral, trimmer and triangle meshes) under different total pressure/ exit pressure combinations, the results are very different from case to case, some even diverged.

 September 17, 2014, 13:52 Need help #2 New Member   Akshay Khadse Join Date: Sep 2013 Posts: 11 Rep Power: 5 Were you able to solve your problem? I also need some help in supersonic wind tunnel CFD. I am designing a Mach 2 wind tunnel, and I am not getting the right results in my CFD. The shock wave is always at the first throat even though I increase the total pressure at inlet. Please suggest the possible solution. Thank you.

 Tags starccm+, supersonic flow

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post ChrisA OpenFOAM Running, Solving & CFD 3 November 13, 2012 19:20 Helmi FLUENT 0 February 4, 2011 05:54 littlelz CFX 4 June 11, 2009 05:51 Marios Vlad CFX 1 February 6, 2008 08:11 Axel Rohde Main CFD Forum 1 November 19, 2001 13:19