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Smaras May 28, 2013 04:33

Steady State Jet Impingement
 
Hello,

I have problem in the start. I am doing this simulation of supersonic jet impingement of air (incompressible ideal) on a flat plate. My settings for simulation are as follows:

operating pressure: 101325 pas

Pressure based+ Steady

1. Model:
Energy+ Kw SST

2. Boundary Condition:
Inlet: velocity input (727.07 m/s)
Outlet: Pressure Outlet 0 gauge pressure

3. Solution Method:
Scheme: Simple
Pressure: Presto
URF: Pressure 0.3 Density/BF 0.5 Momentum 0.5 Tke/SDR 0.8 TV/Energy 1


Now i cannot go further then 20 iterations and its give an error of floating point error.

temperature limited to 1.000000e+00 in 492 cells on zone 12 in domain 1
temperature limited to 5.000000e+03 in 10643 cells on zone 12 in domain 1

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 21 cells
13 6.8784e+03 9.8749e-01 6.2555e-01 3.9413e+07 1.8524e+01 4.4528e-02 3.2878e+06 5:49:40 99987
temperature limited to 1.000000e+00 in 2273 cells on zone 12 in domain 1
temperature limited to 5.000000e+03 in 16155 cells on zone 12 in domain 1

turbulent viscosity limited to viscosity ratio of 1.000000e+05 in 342 cells
14 4.8991e+07 8.0444e-01 1.9110e-01 1.1793e+10 3.9392e+00 9.6625e-01 2.0071e+06 4:39:44 99986

Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature
Divergence detected in AMG solver: temperature temperature limited to 1.000000e+00 in 6325 cells on zone 12 in domain 1

Primitive Error at Node 0: floating point exception

Primitive Error at Node 1: floating point exception

Primitive Error at Node 2: floating point exception

Primitive Error at Node 3: floating point exception

Primitive Error at Node 4: floating point exception


Please if anybody knows about this. Would be thankful for the help.

JimKnopf May 29, 2013 09:40

Hi,

try to deactivate the second order gradients for the temperature.

(rpsetvar 'temperature/secondary-gradient? #f)
(rpsetvar 'temperature/shell-secondary-gradient? #f)


Greetz
Jim

Prince Jassal May 30, 2013 02:05

Error resolved
 
All you need to do is to adjust the under relaxation factors for various field. Its in the solve menu...

Hope it helps

regards,
prince

Smaras May 31, 2013 04:13

Quote:

Originally Posted by JimKnopf (Post 430750)
Hi,

try to deactivate the second order gradients for the temperature.

(rpsetvar 'temperature/secondary-gradient? #f)
(rpsetvar 'temperature/shell-secondary-gradient? #f)


Greetz
Jim

Thanks Jim for replying but by that time i was away and yesterday was holiday in my country.

I have question regarding this isnt used for tetra mesh. Since I am using hexa meshing.

Regards,
Smaras

http://imageshack.us/a/img23/5291/meshe.th.png

Smaras May 31, 2013 04:14

Quote:

Originally Posted by Prince Jassal (Post 430893)
All you need to do is to adjust the under relaxation factors for various field. Its in the solve menu...

Hope it helps

regards,
prince

Thanks Prince,

Did tried that and now comparing my results with compressible flow....with same configuration.

Regards,
Smaras

JimKnopf June 1, 2013 04:01

Hi Smaras,

am I right that you are trying to simulate a supersonic jet with incompressible air? I'm wondering if supersonic flows can be simulated that way, can they?
Did you try to run compressible simulations?

Anyhow impinging jets are a bit nasty. In my cases of subsonic flows we experienced that the RNG and the Realizable k-epsilon model gave a better stability. So you might try a different turbulence model.

Greetz
Jim

Smaras June 4, 2013 04:58

Quote:

Originally Posted by JimKnopf (Post 431313)
Hi Smaras,

am I right that you are trying to simulate a supersonic jet with incompressible air? I'm wondering if supersonic flows can be simulated that way, can they?
Did you try to run compressible simulations?

Anyhow impinging jets are a bit nasty. In my cases of subsonic flows we experienced that the RNG and the Realizable k-epsilon model gave a better stability. So you might try a different turbulence model.

Greetz
Jim

Hello Jim,

yes you are right, i am working on simulating jet with in-compressible air. And till now i am getting good results. As i am counter checking with previous research of Annie Nordquist and Morshed Alam et all research papers for compressible flows.
And no for me KE or even realizable isn't working, and again my supervisors arentz fond of KE :confused:
Now want to find the BC for the same flow rate and pressure profile at the interface. I have some how get some of my result pretty close as my mistake was when i was doing in SST it automatically checked viscous heating which in my case wasn't applicable.

But still i am open for suggestions.

Best Regards


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