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Old   April 20, 2015, 13:32
Default transient calculation
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Ankur Bhatnagar
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Sir ,
I am performing transient calculations over a body using su2. The flow mach number is changing from mach=0.3 to mach=3 .I am working with unstructured gird.As soon as the code reaches Mach =1 it become unstable.So far i have tried using different limiter coeff value ranging from 15 to 0.3 , reducing time step,grid refinement,JST model but problem is still there. can u please suggest me some way to overcome this problem.Thnxx
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Old   April 22, 2015, 15:16
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Quote:
Originally Posted by ankur bhatangar View Post
Sir ,
I am performing transient calculations over a body using su2. The flow mach number is changing from mach=0.3 to mach=3 .I am working with unstructured gird.As soon as the code reaches Mach =1 it become unstable.So far i have tried using different limiter coeff value ranging from 15 to 0.3 , reducing time step,grid refinement,JST model but problem is still there. can u please suggest me some way to overcome this problem.Thnxx
I suggest checking your boundary conditions. Specifically, if you are using an inlet boundary condition try switching to the supersonic inlet condition when the simulation passes Mach 1.0. Note also that the presence of shocks may require significantly more refined grids above Mach 1.0 - ideally you want to have the tightest spacing across the thickness of a shock, and not much larger than the thickness of the shock (numerical methods tend to spread shocks over multiple nodes). Also, depending on your geometry and conditions the presence of shocks may be causing separation - that is, the instability could be physical rather than numerical.
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Old   April 22, 2015, 16:03
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Ankur Bhatnagar
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thnx for your reply sir ...i will surely look into..

I am using unstructured grid all around with riemann boundary conditions.
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