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Time step unsteady nozzle flow, impingement on plate |
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#1 |
Member
Join Date: Nov 2015
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Hello everyone,
I am modeling a nozzle flow impinging on a plate (about 1m away from the nozzle exit), and I would like to monitor the pressure on my plate. (Pressure in the chamber: 90bar, Mach at exit around 3) Since I'm new to unsteady simulations I'ld like to know if anyone has a good rule of thumb to select the time step + number of inner iterations for such a case. |
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#2 | |
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Lane Carasik
Join Date: Aug 2014
Posts: 692
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Quote:
I highly recommend you look into what the CFL (Courant number) number is. This is a basic quantity used for stability of numerical methods and is not meant to be a randomly selected number. Also, I do not believe Star-CCM+ can handle mach flows. Edit: Apparently Star-CCM+ Can handle higher (supersonic and transitional flows). My apologies. Last edited by lcarasik; February 24, 2017 at 12:29. |
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#3 |
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Join Date: Nov 2015
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Hi, thanks for the reply
what i meant with mach at exit is just an indication, and not some value I would use for some boundary condition (i use a stagnation inlet) |
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#4 |
Member
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Hi,
I know that it takes about 10ms to reach my total pressure in the chamber, I will linearly go from 0 to 90bar in 10ms. Is a time step smaller than 1ms necessary? Cheers |
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#5 |
Senior Member
Join Date: Nov 2010
Location: USA
Posts: 1,232
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STAR-CCM+ is perfectly capable of simulating high-mach flows.
Why are you ramping up the inlet pressure? Are you interested in the formation of the jet or only what the jet does after it's formed? As Icarasik said you need to look into the CFL number, it will inform you how big you should make your timestep. However you don't have to make it exactly 1, since this is implicit. |
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Tags |
nozzle flow, time step |
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