How the force derived on a 2D model?

rikio · October 10, 2010, 05:13

As we all know, force is the integral on a wall surface, that means, surface area must not be zero. But my question is, how the force derived on a 2D model which has no area.
For example, the problem of a cylinder in a fluid field. The 2D model in FLUENT is only a circle, the force could be reported that to tell you how much Newton of drag force on the circle is. How this be derived?
Is there any clue in the HELP document?

Thanks in advance.

rikio · October 10, 2010, 05:28

I used to think that the force is based on the existing 2 dimensions of the 2D model and one unit in the other dimension. If the model is built in mm, the third dimension is 1mm. And if in m, it is 1m.

But a model of a 1000mm x 50mm in a 20m/s wind field gets a relatively big drag force, that makes me doubting the derivation.

rikio · October 11, 2010, 21:41

Problem solved.

October 10, 2010, 05:13	How the force derived on a 2D model?	#1
rikio Senior Member Rikio Join Date: Mar 2009 Location: SH, China Posts: 182 Blog Entries: 1 Rep Power: 17	As we all know, force is the integral on a wall surface, that means, surface area must not be zero. But my question is, how the force derived on a 2D model which has no area. For example, the problem of a cylinder in a fluid field. The 2D model in FLUENT is only a circle, the force could be reported that to tell you how much Newton of drag force on the circle is. How this be derived? Is there any clue in the HELP document? Thanks in advance.

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October 10, 2010, 05:28		#2
rikio Senior Member Rikio Join Date: Mar 2009 Location: SH, China Posts: 182 Blog Entries: 1 Rep Power: 17	I used to think that the force is based on the existing 2 dimensions of the 2D model and one unit in the other dimension. If the model is built in mm, the third dimension is 1mm. And if in m, it is 1m. But a model of a 1000mm x 50mm in a 20m/s wind field gets a relatively big drag force, that makes me doubting the derivation.

October 11, 2010, 21:41		#3
rikio Senior Member Rikio Join Date: Mar 2009 Location: SH, China Posts: 182 Blog Entries: 1 Rep Power: 17	Problem solved.