why does drag coefficients turn to negative

bluesky_168 · April 13, 2012, 14:07

I am working on a 2d wings using ANSYS FLUENT 13.0. The fluid is water. The convergence history looks ok for Residual, Cd and Cl, however, the drag coefficients are very close to 0 and turn to negative at last.

Does anyone know what's the problem.

Thank you.

bluesky_168 · April 14, 2012, 22:21

The problem is solved by entering the force vectors: the lift coefficient (-sin, cos), the drag coefficient (cos, sin).

bluesky_168 · April 16, 2012, 13:54

The negative drag coefficient again in a smaller angle of attack.

Why?

banty · April 16, 2012, 15:26

why u are doing calculating lift and drag coefficient manually. u can report the drag and lift coefficient in fluent even u can set as monitor. plz also check the reference area that is used for calculating drag and lift coefficient.

April 13, 2012, 14:07	why does drag coefficients turn to negative	#1
bluesky_168 New Member no Join Date: Mar 2012 Posts: 6 Rep Power: 15	I am working on a 2d wings using ANSYS FLUENT 13.0. The fluid is water. The convergence history looks ok for Residual, Cd and Cl, however, the drag coefficients are very close to 0 and turn to negative at last. Does anyone know what's the problem. Thank you.

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April 14, 2012, 22:21		#2
bluesky_168 New Member no Join Date: Mar 2012 Posts: 6 Rep Power: 15	The problem is solved by entering the force vectors: the lift coefficient (-sin, cos), the drag coefficient (cos, sin).

April 16, 2012, 13:54		#3
bluesky_168 New Member no Join Date: Mar 2012 Posts: 6 Rep Power: 15	The negative drag coefficient again in a smaller angle of attack. Why?

April 16, 2012, 15:26		#4
banty Member banty Join Date: Mar 2012 Posts: 52 Rep Power: 15	why u are doing calculating lift and drag coefficient manually. u can report the drag and lift coefficient in fluent even u can set as monitor. plz also check the reference area that is used for calculating drag and lift coefficient.