tornado simulation in CFD

shoumo_30 · April 20, 2013, 03:31

Hello everyone. I am trying to create a tornado inside a cylinder (2.07 m in height and .4m in radius. The lower part (height = .41m) of the cylinder is the velocity inlet for which I have a UDF function. Rest of the height is sidewall. I have pretty fine mesh near the base and also near the side wall so that I can use enhanced wall treatment. I also adapted the grid in fluent. although I am trying run an unsteady simulation my iteration shows some AMG divergance after sometimes. I am using Reynolds stress model and sidewall is free shear wall. Outlet is normal outflow (top of the cylinder). My mesh size is .025 but near the base and sidewall it is more fine. Thanks in advance for your helps.

Zoheb

mohit juneja · April 20, 2013, 17:07

i m working on star ccm can any one tell me pls what are the inital conditions for exhaust muffler like what is the temo. value, inlet velocity, maSS FLOW RATE & WILL I HAVE TO GIVE ALL THESE VALUE OR ONLY ONE ?

RodriguezFatz · April 22, 2013, 04:26

Which solver do you use?
Also please tell us all discretization schemes.

Ravindra Shende · December 7, 2017, 10:24

Hi Zoheb,

I am not sure what is causing the divergence but I think the boundary condition at the top of the cylinder might have something to do with it.

At the top boundary you will have both inflow (at the center) and outflow (at the edges) as the tornado is forming in your unsteady simulations. I am not sure how well the normal outflow boundary condition will be able to handle this situation. The total mass inflow through the top surface should match the total mass outflow through the same surface at all time steps.

I hope this gives you something to think about (unless you have already given it a thought, in which case just ignore all this).

April 20, 2013, 03:31	tornado simulation in CFD	#1
shoumo_30 New Member Zoheb Nasir Join Date: Nov 2011 Location: London, Ontario Posts: 7 Rep Power: 14	Hello everyone. I am trying to create a tornado inside a cylinder (2.07 m in height and .4m in radius. The lower part (height = .41m) of the cylinder is the velocity inlet for which I have a UDF function. Rest of the height is sidewall. I have pretty fine mesh near the base and also near the side wall so that I can use enhanced wall treatment. I also adapted the grid in fluent. although I am trying run an unsteady simulation my iteration shows some AMG divergance after sometimes. I am using Reynolds stress model and sidewall is free shear wall. Outlet is normal outflow (top of the cylinder). My mesh size is .025 but near the base and sidewall it is more fine. Thanks in advance for your helps. Zoheb Last edited by shoumo_30; April 20, 2013 at 11:52.

April 20, 2013, 17:07	cfd analysis of muffler for calculating bck pressure	#2
mohit juneja New Member mohit Join Date: Apr 2013 Posts: 1 Rep Power: 0	i m working on star ccm can any one tell me pls what are the inital conditions for exhaust muffler like what is the temo. value, inlet velocity, maSS FLOW RATE & WILL I HAVE TO GIVE ALL THESE VALUE OR ONLY ONE ?

April 22, 2013, 04:26		#3
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	Which solver do you use? Also please tell us all discretization schemes. __________________ The skeleton ran out of shampoo in the shower.

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December 7, 2017, 10:24		#4
Ravindra Shende Member Ravindra Shende Join Date: Feb 2011 Location: Pune, India Posts: 45 Rep Power: 15	Hi Zoheb, I am not sure what is causing the divergence but I think the boundary condition at the top of the cylinder might have something to do with it. At the top boundary you will have both inflow (at the center) and outflow (at the edges) as the tornado is forming in your unsteady simulations. I am not sure how well the normal outflow boundary condition will be able to handle this situation. The total mass inflow through the top surface should match the total mass outflow through the same surface at all time steps. I hope this gives you something to think about (unless you have already given it a thought, in which case just ignore all this).