URANS

November 29, 2006, 07:33

I am going to perform the Unsteady RANS simulation to analyze cavity flow oscillations. I have no idea about the time step. I will be grateful if some one could tell me how can I choose the time step for the first order implicit time advancing.

November 29, 2006, 08:55

Determine the oscillation frequencies of the cavity using Rossiter's formula. For the highest frequency you want to try to capture, plan on 50-100 timesteps per period. Back out the timestep. Using URANS you'll be lucky to get the second harmonic, so there's no point in going to a much higher frequency. And first-order time is not a good choice for simulating unsteady flows - you really need to use second-order time differencing.

November 30, 2006, 04:31

In addition

If these calculations will be used to exstimate noise--> RANS is not the best way ....

November 30, 2006, 10:10

Thanks to all of you.

November 29, 2006, 07:33	URANS	#1
Magic Guest Posts: n/a	I am going to perform the Unsteady RANS simulation to analyze cavity flow oscillations. I have no idea about the time step. I will be grateful if some one could tell me how can I choose the time step for the first order implicit time advancing.

November 29, 2006, 08:55	Re: URANS	#2
ag Guest Posts: n/a	Determine the oscillation frequencies of the cavity using Rossiter's formula. For the highest frequency you want to try to capture, plan on 50-100 timesteps per period. Back out the timestep. Using URANS you'll be lucky to get the second harmonic, so there's no point in going to a much higher frequency. And first-order time is not a good choice for simulating unsteady flows - you really need to use second-order time differencing.

November 30, 2006, 04:31	Re: URANS	#3
Mar Guest Posts: n/a	In addition If these calculations will be used to exstimate noise--> RANS is not the best way ....

November 30, 2006, 10:10	Re: URANS	#4
Magic Guest Posts: n/a	Thanks to all of you.

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