lift coefficent of ahmed body

unisimo · April 8, 2009, 04:50

hi,i am using fluent to do external air flow analysis around the ahmed body at 60m/s. the drag coefficent(0.28) is closed to the experiment result(0.285 for slant 25degree),but the lift coefficent(0.001) is far smaller than the experiment result(0.4). I have used several models, unfortunately, there is no improvement on lift coefficient.I have do these in CFX with the same mesh. the Cl is close to the experiment result, but it fluctuate from 0.2 to 0.7

please give me some suggestions

simo

Hertzel · May 14, 2009, 18:48

hi,
could you give some more details about the mesh you used?
how fine it is in the region directly around the body and further away?

how do the velocity plots on some lines behind the body (and on the slant surface) match the ones from the literature or simulations by Lienhart?
(the data of Lienhart's velocity plots can be found easily on the internet)

Greetings
Hertzel

Ralf Schmidt · May 15, 2009, 05:11

do you model in 2D? Then, you have to set the area in the reference values panel to the are that that is needed for lift coefficient calculation....

Shamoon Jamshed · May 18, 2009, 14:30

Well the mesh is structures. All the results, vel profile, stream lines are correct. The only problem is the area. In 2D I dont know how to specify the area for each individual wall!

Fluent manual didnot help

April 8, 2009, 04:50	lift coefficent of ahmed body	#1
unisimo New Member simo Join Date: Apr 2009 Posts: 2 Rep Power: 0	hi,i am using fluent to do external air flow analysis around the ahmed body at 60m/s. the drag coefficent(0.28) is closed to the experiment result(0.285 for slant 25degree),but the lift coefficent(0.001) is far smaller than the experiment result(0.4). I have used several models, unfortunately, there is no improvement on lift coefficient.I have do these in CFX with the same mesh. the Cl is close to the experiment result, but it fluctuate from 0.2 to 0.7 please give me some suggestions simo

May 15, 2009, 05:11		#3
Ralf Schmidt Member Ralf Schmidt Join Date: Mar 2009 Location: Austria Posts: 67 Rep Power: 17	do you model in 2D? Then, you have to set the area in the reference values panel to the are that that is needed for lift coefficient calculation.... __________________ CFD - nothing but Colourful Fluid Dynamics

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May 14, 2009, 18:48		#2
Hertzel New Member Join Date: Apr 2009 Posts: 4 Rep Power: 17	hi, could you give some more details about the mesh you used? how fine it is in the region directly around the body and further away? how do the velocity plots on some lines behind the body (and on the slant surface) match the ones from the literature or simulations by Lienhart? (the data of Lienhart's velocity plots can be found easily on the internet) Greetings Hertzel

May 18, 2009, 14:30		#4
Shamoon Jamshed Senior Member Shamoon Jamshed Join Date: Apr 2009 Location: Karachi Posts: 381 Rep Power: 18	Well the mesh is structures. All the results, vel profile, stream lines are correct. The only problem is the area. In 2D I dont know how to specify the area for each individual wall! Fluent manual didnot help