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Supersonic flow
Posted 2011年7月4日 GMT-4 03:30 Fluid & Heat, Computational Fluid Dynamics (CFD) Version 4.1 2 Replies
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The approach to the problem begins with a half cone geometry of 8* half-angle and a rectangular box(15-times larger than maximum dimension of half cone)
I am using COMSOL 4.1 with non-isothermal flow module(laminar)
The rectangular box has following boundary conditions
1>inlet-velocity,constant temperature
2>outlet-pressure,outflow
3>outer wall opposite to half-cone(slip)
4>wall containing half-cone(slip-axis symmteric)
5>half-cone surface(no slip)
Study Type
-stationary solver
Approach
I started with inlet velocity 20m/s and kept this as initial condition for inlet velocity 50m/s and so on in steps of 30m/s.
I refined the mesh as and when required as per the physics and the way of meshing was well taken care. As i increased inlet velocity, i was slowly decreasing outlet pressure also. The results were satisfactory till 250m/s-inlet and outlet pressure-0.4[atm].
Issue
After 250m/s with all possible and careful configuration of solver setting and meshing the results are distorted for
inlet-260m/s and after this it doesnot converge properly. Maximum i have gone upto 280/m/s-inlet with step increase reduced to 5m/s.
How can i curb this problem ?Do i need to change CFL number?
Additional information
>>Relative tolerence(0.001)
>>used both Pardiso or iterative(krylov-preconditioning) with fully coupled
>>cone is spherically blunted
>>automatic damping [varied both i)step for update(2-5) ii)minimum dampin factor(10^-4 to 10^-8)]
>>configuration of computer 8GB RAM quad core also 32GB RAM server was also used
>>Ck=0.5-0.75 was used in consistent stabilization
>>inconsistent stabilization was never used as it would affect the physics
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The best way to model supersonic flows is to use the High Mach Number Flow (HMNF) interface available in COMSOL Multiphysics 4.2.
Best regards,
Zoran
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Thank you for your reply. I am aware of the module(HMNF) in comsol 4.2. But all i want to know whether is it possible to use non-isothermal flow module for supersonic flow because i am presently using comsol 4.1. If at all there is no point in trying in non-isothermal flow i will switch to comsol 4.2 as you have advised.
GV