stopping and re-starting moving mesh for static lift coefficients

haconk · April 20, 2009, 05:19

I'd like to calculate the static lift, moment and drag coefficients for various angles of incidence.

I created one model with a moving mesh but how do I make that transient model a stationary one within the run-time environment?

Or do I need to create individual models and do separate runs for each angle of incidence?

ghorrocks · April 20, 2009, 18:42

Hi,

Using moving mesh to do various AOA is a very complicated way of doing it. Just change the angle of incidence at the inlet boundary. If it is a simple steady case then use a simple steady model.

Glenn Horrocks

haconk · April 21, 2009, 06:18

Thanks Glenn,

I have a moving anyway for the transient runs, besides the model actually changes with various AOA (actively controlled), that's why I'd like to use the moving mesh method.

Just wondered whether I could obtain the stationary results by stopping and restarting the run and if so, how? Couldn't find anything in the manual re this.

ghorrocks · April 21, 2009, 07:16

Hi,

You can't use moving mesh in steady state runs. Also I don't think you can move a mesh to a position and use that mesh for a steady state run.

You would only bother doing a moving mesh simulation of what you are doing if the flow timescales are similar to the wing motion timescales. If the wing is much slower than the air it can be accurately modelled as a series of steady state models at the various positions.

Glenn Horrocks

Tristan · April 27, 2009, 16:05

We have done some moving mesh simulations to get "steady-state" port discharge coefficients as the ports are closed. Rather than generate a sequence of meshes and run them steady-state one at a time, we did a moving mesh transient simulation where the ports closed very slowly. In order to make sure our results were "steady-state", we did a 2nd run where it took twice as long to close the ports. A comparison of the two runs showed no difference between them until the ports were nearly closed.

I doubt that this was the most efficient way to solve the problem but it sounds like it might be an option for you.

Tristan

April 20, 2009, 05:19	stopping and re-starting moving mesh for static lift coefficients	#1
haconk New Member Tim B Join Date: Apr 2009 Posts: 11 Rep Power: 17	I'd like to calculate the static lift, moment and drag coefficients for various angles of incidence. I created one model with a moving mesh but how do I make that transient model a stationary one within the run-time environment? Or do I need to create individual models and do separate runs for each angle of incidence?

April 20, 2009, 18:42		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, Using moving mesh to do various AOA is a very complicated way of doing it. Just change the angle of incidence at the inlet boundary. If it is a simple steady case then use a simple steady model. Glenn Horrocks

April 21, 2009, 06:18		#3
haconk New Member Tim B Join Date: Apr 2009 Posts: 11 Rep Power: 17	Thanks Glenn, I have a moving anyway for the transient runs, besides the model actually changes with various AOA (actively controlled), that's why I'd like to use the moving mesh method. Just wondered whether I could obtain the stationary results by stopping and restarting the run and if so, how? Couldn't find anything in the manual re this.

April 21, 2009, 07:16		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, You can't use moving mesh in steady state runs. Also I don't think you can move a mesh to a position and use that mesh for a steady state run. You would only bother doing a moving mesh simulation of what you are doing if the flow timescales are similar to the wing motion timescales. If the wing is much slower than the air it can be accurately modelled as a series of steady state models at the various positions. Glenn Horrocks

April 27, 2009, 16:05		#5
Tristan Member Tristan Burton Join Date: Mar 2009 Posts: 43 Rep Power: 17	We have done some moving mesh simulations to get "steady-state" port discharge coefficients as the ports are closed. Rather than generate a sequence of meshes and run them steady-state one at a time, we did a moving mesh transient simulation where the ports closed very slowly. In order to make sure our results were "steady-state", we did a 2nd run where it took twice as long to close the ports. A comparison of the two runs showed no difference between them until the ports were nearly closed. I doubt that this was the most efficient way to solve the problem but it sounds like it might be an option for you. Tristan