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help with boundary profile in pressure inlet

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Old   June 17, 2013, 14:57
Default help with boundary profile in pressure inlet
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Hi
I built a 2-d model, using pressure inlet and pressure outlet.
I have the experimental inlet boundary total pressure data(attached). I used these data for a boundary profile.

~~~~~~~~~~~~~~~~~~~~~~ I saved the mesh file, boundary profile and other conditions in a gmail account (fluent111, PIN:1234506789), if anyone interested, please go to have a look.~~~~~~~~~~~~~~~


the other settings are as below:
operating pressure : 0 psi
pressure inlet total pressure : profile
pressure inlet static pressure : 9.819 psi
pressure out static pressure : 14.7 psi
total temperature for all is 300 K

The problem is: when I choose inlet as compute from, it shows "_1.#IND" for x velocity, y velocity, turbulent kinetic energy, and turbulent dissipation rate, and "_1.#INF" for temperature.

I cannot run, it give me AMG error directly.

If I still use the boudanry profile as the pressure inlet total pressure, but input values for x velocity, y velocity, turbulent kinetic energy, and turbulent dissipation rate, and temperature for initialization, I can run it only when X velocity was set below 300 m/s, if it was set above 300m/s, it gave me the AMG divergence directly. But with 300m/s, the results is not right.

Anybody has any idea about this?
Thanks
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File Type: png BL profile.PNG (19.8 KB, 14 views)

Last edited by quiqui; June 18, 2013 at 11:38. Reason: attached BL profile
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Old   June 18, 2013, 01:09
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do you have 2 inlets with different settings?
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Old   June 18, 2013, 09:37
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no, I only have one inlet, one outlet.
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Old   June 18, 2013, 09:46
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attached is the sketch and profile data.
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File Type: png profile data.PNG (12.5 KB, 7 views)
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Old   June 18, 2013, 09:54
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I know that I always had some unstabilities with pressure-inlet/pressure-outlet.
Are you computing compressible?
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Old   June 18, 2013, 10:06
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Are you saying that your expect your result to depend on the initialization? Or what do you mean by "But with 300m/s, the results is not right."?
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Old   June 18, 2013, 10:07
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Quote:
Originally Posted by -mAx- View Post
I know that I always had some unstabilities with pressure-inlet/pressure-outlet.
Are you computing compressible?
yes, supersonic flow with Mach number 1.9 @ total pressure 70 psi, and total temperature 300 K.
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Old   June 18, 2013, 10:10
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Quote:
Originally Posted by quiqui View Post
yes, supersonic flow with Mach number 1.9 @ total pressure 70 psi, and total temperature 300 K.
In your initial post you write:
operating pressure : 0 psi
Shouldn't that be 70 then?
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Old   June 18, 2013, 10:11
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Quote:
Originally Posted by quiqui View Post
yes, supersonic flow with Mach number 1.9 @ total pressure 70 psi, and total temperature 300 K.
Ok then try to compute first without profile for checking if your setup is ok.
One stupid question: on your profile, I see you have points with total pressure = 0 psi -->
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Old   June 18, 2013, 10:13
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Quote:
Originally Posted by RodriguezFatz View Post
Are you saying that your expect your result to depend on the initialization? Or what do you mean by "But with 300m/s, the results is not right."?
If I initialized the x velocity with 300 m/s, the computing velocity result cannot reach the actual velocity.
In experiments, with total pressure @ 70 psi, total temperature 300k, static pressure 9.819psi @ inlet, the velocity is M=1.9, which is around 500 m/s.

without importing the data profile, the computing results are similar with experimental, but once importing the boundary total pressure data profile, all the problems I mentioned above appeared.
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Old   June 18, 2013, 10:16
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Quote:
Originally Posted by -mAx- View Post
Ok then try to compute first without profile for checking if your setup is ok.
One stupid question: on your profile, I see you have points with total pressure = 0 psi -->
yes, there is 0 psi, which is @ the wall.

I tried running without profile, it gave the experimental trend, but after some running, I import the profile, It gave me the error immediately.
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Old   June 18, 2013, 10:18
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Quote:
Originally Posted by RodriguezFatz View Post
In your initial post you write:
operating pressure : 0 psi
Shouldn't that be 70 then?
in supersonic case, operating pressure is 0.
70 psi is the total pressure.
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Old   June 18, 2013, 10:18
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Quote:
Originally Posted by quiqui View Post
Hi
I built a 2-d model, using pressure inlet and pressure outlet.

I have the experimental inlet boundary total pressure data(attached). I used these data for a boundary profile.

the other settings are as below:
operating pressure : 0 psi
pressure inlet total pressure : profile
pressure inlet static pressure : 9.819 psi
pressure out static pressure : 14.7 psi
total temperature for all is 300 K

The problem is: when I choose inlet as compute from, it shows "_1.#IND" for x velocity, y velocity, turbulent kinetic energy, and turbulent dissipation rate, and "_1.#INF" for temperature.

I cannot run, it give me AMG error directly.

If I still use the boudanry profile as the pressure inlet total pressure, but input values for x velocity, y velocity, turbulent kinetic energy, and turbulent dissipation rate, and temperature for initialization, I can run it only when X velocity was set below 300 m/s, if it was set above 300m/s, it gave me the AMG divergence directly. But with 300m/s, the results is not right.

Anybody has any idea about this?
Thanks
can you share your geometry, mesh and pressure profile?
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Old   June 18, 2013, 10:21
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Quote:
Originally Posted by Far View Post
can you share your geometry, mesh and pressure profile?
to capture the shock with separation, the mesh is very fine, so I only posted the geometry.
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Old   June 18, 2013, 10:22
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Quote:
Originally Posted by quiqui View Post
yes, there is 0 psi, which is @ the wall.

I tried running without profile, it gave the experimental trend, but after some running, I import the profile, It gave me the error immediately.
How can you have total pressure 0 psi at wall (at inlet)?
At wall you have no velocity (if stationnary wall), which means no dymamic pressure. But the static pressure should remain. (ptot= pstatic + pdynamic = pstatic + 0 = pstatic )
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Old   June 18, 2013, 10:31
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Quote:
Originally Posted by -mAx- View Post
How can you have total pressure 0 psi at wall (at inlet)?
At wall you have no velocity (if stationnary wall), which means no dymamic pressure. But the static pressure should remain. (ptot= pstatic + pdynamic = pstatic + 0 = pstatic )
yes, I notice this. I will remove the o points and try.
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Old   June 18, 2013, 10:35
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Quote:
Originally Posted by -mAx- View Post
How can you have total pressure 0 psi at wall (at inlet)?
At wall you have no velocity (if stationnary wall), which means no dymamic pressure. But the static pressure should remain. (ptot= pstatic + pdynamic = pstatic + 0 = pstatic )
I revised the o psi to the static pressure and tried, it gave the same error when compute from inlet.
still cannot run the case
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Old   June 18, 2013, 10:51
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If you can share your mesh, then we can try to rectify problem...
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Old   June 18, 2013, 11:12
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Quote:
Originally Posted by Far View Post
If you can share your mesh, then we can try to rectify problem...
hi
I saved the mesh file and profile in draft @ a gmail account

user: fluent111
password: 1234506789

thanks
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Old   June 18, 2013, 12:23
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Using density based solver (uniform inlet pressure, averaged from pressure profile data) and solver is running without problems.

Few points :

1. Mesh is not good enough

2. Place outlet further downstream.

3. Check boundary conditions
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