grid independence study in transition simulation

littlelz · March 27, 2009, 12:26

i am just wondering what variables are supposed to be compared as we do grid independence study for a transition simulation. i Guess transition location on the body is supposed to be one of them, any other key variables?

many thanks

triple_r · March 27, 2009, 13:04

Hi,

Have you thought of an integral variable too? (like shear force on wall or something like that)

And also a very simple question, what kind of flow are you trying to simulate using the transition model? Because you know that the transition model in CFX has been tuned for flat plate problem, or external flows at best.

littlelz · March 28, 2009, 06:15

acturally, we are checking forces and moments too. but the problem is they are changing little, while the transition location change a lot. so I don't know if the mesh is independent or not.

for your info, we are doing transition simulation for external flow.

many thanks for your reply

triple_r · March 28, 2009, 11:02

I think as for some variables it is harder to achieve mesh independence than the others, you should at the variables that are very important to you, and the variables that you are looking to take out of the simulation.
If the main point of this simulation is to get transition location, then you need to work more on the mesh, and increase its resolution a lot, but if the only important thing (the outcome that you expect) are the forces, then you have reached mesh independence.

littlelz · March 30, 2009, 08:16

thanks a lot. i got your point and will try more refine mesh.

all the best

March 27, 2009, 12:26	grid independence study in transition simulation	#1
littlelz New Member Join Date: Mar 2009 Posts: 24 Rep Power: 17	i am just wondering what variables are supposed to be compared as we do grid independence study for a transition simulation. i Guess transition location on the body is supposed to be one of them, any other key variables? many thanks

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March 27, 2009, 13:04		#2
triple_r Senior Member Reza Join Date: Mar 2009 Location: Appleton, WI Posts: 116 Rep Power: 17	Hi, Have you thought of an integral variable too? (like shear force on wall or something like that) And also a very simple question, what kind of flow are you trying to simulate using the transition model? Because you know that the transition model in CFX has been tuned for flat plate problem, or external flows at best.

March 28, 2009, 06:15		#3
littlelz New Member Join Date: Mar 2009 Posts: 24 Rep Power: 17	acturally, we are checking forces and moments too. but the problem is they are changing little, while the transition location change a lot. so I don't know if the mesh is independent or not. for your info, we are doing transition simulation for external flow. many thanks for your reply

March 28, 2009, 11:02		#4
triple_r Senior Member Reza Join Date: Mar 2009 Location: Appleton, WI Posts: 116 Rep Power: 17	I think as for some variables it is harder to achieve mesh independence than the others, you should at the variables that are very important to you, and the variables that you are looking to take out of the simulation. If the main point of this simulation is to get transition location, then you need to work more on the mesh, and increase its resolution a lot, but if the only important thing (the outcome that you expect) are the forces, then you have reached mesh independence.

March 30, 2009, 08:16		#5
littlelz New Member Join Date: Mar 2009 Posts: 24 Rep Power: 17	thanks a lot. i got your point and will try more refine mesh. all the best