Supersonic flow over ramp

srinath · June 13, 2008, 04:05

Hello

i am trying to model supersonic flow over a ramp.
These are my bc's and domain.

Inlet--supersonic inlet (P,U,T) specified.

Outlet--Extrapolated outlet (dp/dn,du/dn.dT/dn=0),
since flow at outlet is supersonic.

top of channel--symmetry(to simulate an infinite domain).

bottom of channel before ramp--symmetry.

ramp--slip.

When i run the case with these bc's, the solution blows up.
I would appreciate it if someone tell me what i am doing wrong

Regards
Srinath

srinath · June 14, 2008, 03:07

Solved it, was using wrong values of R and Cv

varun · June 16, 2008, 08:43

Hi Srinath

I used the same conditions and could not solve the problem - the solutiuon blew up. I used U = 2, p = 1, T = 1, Cv = 1.785, R = 0.714. What values didi you use?

How far above the ramp did u put you rfarfiedl condition?

Regards
Varun

srinath · June 16, 2008, 09:58

Hi Vikas

I converted everything to SI, since otherwise comparison won't be correct. R=.714,Cv=1.785 does not correspond to air, for which we have test results.
Domain is exactly as on the nasa webpage
http://www.lerc.nasa.gov/WWW/wind/va...dge/wedge.html
with symmetry bc at top of domain.

I used R=287(for air), then get Cv(assume gamma=1.4), then a, then U = 2.5*a
similarly convert P,T etc in NASA problem to SI

Note that i ran it for Mach no=2.5(not 2.0), Angle was underpredicted by about 5 degrees.

Regards
Srinath

June 13, 2008, 04:05	Hello i am trying to model	#1
srinath Member srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 91 Rep Power: 17	Hello i am trying to model supersonic flow over a ramp. These are my bc's and domain. Inlet--supersonic inlet (P,U,T) specified. Outlet--Extrapolated outlet (dp/dn,du/dn.dT/dn=0), since flow at outlet is supersonic. top of channel--symmetry(to simulate an infinite domain). bottom of channel before ramp--symmetry. ramp--slip. When i run the case with these bc's, the solution blows up. I would appreciate it if someone tell me what i am doing wrong Regards Srinath

June 14, 2008, 03:07	Solved it, was using wrong val	#2
srinath Member srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 91 Rep Power: 17	Solved it, was using wrong values of R and Cv

June 16, 2008, 08:43	Hi Srinath I used the same	#3
varun New Member Varun Vikas Join Date: Mar 2009 Posts: 17 Rep Power: 17	Hi Srinath I used the same conditions and could not solve the problem - the solutiuon blew up. I used U = 2, p = 1, T = 1, Cv = 1.785, R = 0.714. What values didi you use? How far above the ramp did u put you rfarfiedl condition? Regards Varun

June 16, 2008, 09:58	Hi Vikas I converted everyt	#4
srinath Member srinath Join Date: Mar 2009 Location: Champaign, USA Posts: 91 Rep Power: 17	Hi Vikas I converted everything to SI, since otherwise comparison won't be correct. R=.714,Cv=1.785 does not correspond to air, for which we have test results. Domain is exactly as on the nasa webpage http://www.lerc.nasa.gov/WWW/wind/va...dge/wedge.html with symmetry bc at top of domain. I used R=287(for air), then get Cv(assume gamma=1.4), then a, then U = 2.5*a similarly convert P,T etc in NASA problem to SI Note that i ran it for Mach no=2.5(not 2.0), Angle was underpredicted by about 5 degrees. Regards Srinath

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