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Old   March 13, 2006, 16:35
Default solver is not converging
Vijesh Joshi
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My name is Vijesh Joshi. I am a student in karnataka (India) doing my M.Tech in SDM engineering college-Dharwad. I am trying to reduce the drag by the spike attachment for a 120deg blunt cone nose. I was inspired and motivated by going through your doctorate thesis. I am going wrong somewhere by which the solver is not converging. Below I have written the geometry details, PRE-settings and solver control settings which I had kept for my problem.

Geometry details

L(spike length) = 200 mm

D(model base dia) = 300 mm

at the tip of the spike, an aerodisc of 40mm radius is being attached.

PRE settings

1. fluid domain - air ideal gas, reference pressure= 1 Pa, Laminar flow and other parameters not changed.

2. inlet - Supersonic, M2=644 m/sec, static pre=0.5643 atm, static temp = 258.3 K and others not changed.

3. Outlet - supersonic.

Solver settings

Equations - all were set to upwind scheme.

time scale - local time scale factor=0.9

residual = 1e-4 = 0.0001

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Old   March 13, 2006, 19:42
Default Re: solver is not converging
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Try using the shear stress transportation model for turbulence.iam not sure why you are using the laminar flow.At super sonic speed i would presume the air to be turbulent.

Change the solver settings to high resolution.upwind is more robust and can be used for intial set of results but for accurate final one use the high resolution.

Change the reference pressure to Zero.

Set your time scale to auto and if you monitor the equations and if it is converging then change the settings while the solver is runnin using the edit form and change to physical time scale.

When it is starting to solve it will give you the auto time scale.use that to set the physical time scale to get a faster convergence.

Hope these are helpful

Thanks Regards Rajit
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Old   March 13, 2006, 23:33
Default Re: solver is not converging
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What do you mean by "not converging"? Is the residual plot showed a diverging behaviour or is it just not reaching the target residual?

Is there a reason why you apply laminar flow assumption for such high Reynolds no? I'm not sure about the physics of your flow structures but you must make sure that the condition that you applied is realistic.
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Old   March 18, 2006, 10:08
Default Re: solver is not converging
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how about your meshing?
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