Off drag coefficient

jackwabbit · February 21, 2013, 00:15

Yes, hello, I'm currently working on the numerical analysis of flow around an Ahmed body with a rear slant angle of 35 using Star ccm+. I'm getting a value of 1 for the total drag coefficient when the validated value is around 0.25. I've more or less checked everything so I'm going to go with a error in the mesh. If it's the mesh or not the mesh, any suggestions on what could be the problem?

siara817 · February 21, 2013, 05:33

You can refine the mesh and check the value of drag coefficient. The mesh must be improved until you the drag coefficient become constant.

jackwabbit · February 21, 2013, 06:02

Oh alright, thank you! The force coefficient does become a constant does become constant but just at the wrong value. And yes, I'll work on refining the mesh. Are there any recommended range of values for the mesh size for this case? Since the Ahmed body analysis is a pretty standard one.

siara817 · February 22, 2013, 02:38

As you said at your first post, the drag coefficient should be around 0.25. Do you use k-omeg?

jackwabbit · February 22, 2013, 07:19

Nope. I've been using K-epsilon till now, will try k omega and get back. Which model would you say would be appropriate: the standard model or the SST one?

February 21, 2013, 00:15	Off drag coefficient	#1
jackwabbit New Member Anonymous 92 Join Date: Feb 2013 Posts: 18 Rep Power: 13	Yes, hello, I'm currently working on the numerical analysis of flow around an Ahmed body with a rear slant angle of 35 using Star ccm+. I'm getting a value of 1 for the total drag coefficient when the validated value is around 0.25. I've more or less checked everything so I'm going to go with a error in the mesh. If it's the mesh or not the mesh, any suggestions on what could be the problem?

February 21, 2013, 05:33		#2
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 17	You can refine the mesh and check the value of drag coefficient. The mesh must be improved until you the drag coefficient become constant. __________________ Good luck Siamak

February 22, 2013, 02:38		#4
siara817 Senior Member siamak rahimi ardkapan Join Date: Jul 2010 Location: Copenhagen, Denmark Posts: 220 Rep Power: 17	As you said at your first post, the drag coefficient should be around 0.25. Do you use k-omeg? __________________ Good luck Siamak

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February 21, 2013, 06:02		#3
jackwabbit New Member Anonymous 92 Join Date: Feb 2013 Posts: 18 Rep Power: 13	Oh alright, thank you! The force coefficient does become a constant does become constant but just at the wrong value. And yes, I'll work on refining the mesh. Are there any recommended range of values for the mesh size for this case? Since the Ahmed body analysis is a pretty standard one.

February 22, 2013, 07:19		#5
jackwabbit New Member Anonymous 92 Join Date: Feb 2013 Posts: 18 Rep Power: 13	Nope. I've been using K-epsilon till now, will try k omega and get back. Which model would you say would be appropriate: the standard model or the SST one?