NACA 4 digit simulation - not converging

dublin · April 23, 2009, 07:11

I'm doing simulations on a NACA 2408 aerofoil, and at angles of attack of about 10degrees or greater it just won't converge, and normally the graph that shows when the solver is running falls into a periodic pattern. I've tried the simulation with various meshes (i.e. more elements in the mesh) and added layers to the inflation boundary around the aerofoil without luck. I've also tried to change from Auto timestep to physical timestep, trying a couple of values there but still no luck. I'm running SST turbulence, and it's a steady state simulation. I'm a complete novice with CFX and any tips on how to get it to converge would be much appreciated, thanks.

ghorrocks · April 23, 2009, 19:36

hi,

Have a look at:

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

I bet it is going transient as you approach the stall point.

Glenn Horrocks

dublin · April 24, 2009, 08:27

Thanks for that. Not really sure what I'm doing now but I'll see if I can get it to run as a transient simulation.

April 23, 2009, 07:11	NACA 4 digit simulation - not converging	#1
dublin New Member Join Date: Apr 2009 Posts: 2 Rep Power: 0	I'm doing simulations on a NACA 2408 aerofoil, and at angles of attack of about 10degrees or greater it just won't converge, and normally the graph that shows when the solver is running falls into a periodic pattern. I've tried the simulation with various meshes (i.e. more elements in the mesh) and added layers to the inflation boundary around the aerofoil without luck. I've also tried to change from Auto timestep to physical timestep, trying a couple of values there but still no luck. I'm running SST turbulence, and it's a steady state simulation. I'm a complete novice with CFX and any tips on how to get it to converge would be much appreciated, thanks.

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April 23, 2009, 19:36		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	hi, Have a look at: http://www.cfd-online.com/Wiki/Ansys...gence_criteria I bet it is going transient as you approach the stall point. Glenn Horrocks

April 24, 2009, 08:27		#3
dublin New Member Join Date: Apr 2009 Posts: 2 Rep Power: 0	Thanks for that. Not really sure what I'm doing now but I'll see if I can get it to run as a transient simulation.