Flow forces

Tunlu · August 18, 2013, 20:59

Hi, Everybody !

I would like to request to share me your knowledge !
I am working on flow force acting on a suspended bar by using Fluent.
The flow is perpendicularly targeted (let say Z direction) on a surface of the bar (let say X-Y plane) . I got the results ! When I extracted the flow force acting on that surface in Z direction, there was viscous force.
I would like to know Why? Thank you very much.

Tl

flotus1 · August 19, 2013, 02:15

How high is the contribution of shear forces to the total force?
Are you sure that it is not just a numerical artifact caused by the fact that the normal vector of the face (especially the normal vectors of the cell faces) are never identical with the z-direction?

Tunlu · August 20, 2013, 07:01

Yes, Flotus1

The percentage of viscous force is about 0.2%. But, I like to see it as totally zero. It may be because of the fact that you said. Normal vector of faces of some element are not identical to the Z axis. Thus, viscous forces on that surface produce components in Z-axis. Right? So, we should not take account that viscous force, Right? Thank you very much, Flotus1.

Tunlu

August 18, 2013, 20:59	Flow forces	#1
Tunlu New Member Tunlu Join Date: Aug 2013 Posts: 10 Rep Power: 12	Hi, Everybody ! I would like to request to share me your knowledge ! I am working on flow force acting on a suspended bar by using Fluent. The flow is perpendicularly targeted (let say Z direction) on a surface of the bar (let say X-Y plane) . I got the results ! When I extracted the flow force acting on that surface in Z direction, there was viscous force. I would like to know Why? Thank you very much. Tl

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August 19, 2013, 02:15		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	How high is the contribution of shear forces to the total force? Are you sure that it is not just a numerical artifact caused by the fact that the normal vector of the face (especially the normal vectors of the cell faces) are never identical with the z-direction?

August 20, 2013, 07:01		#3
Tunlu New Member Tunlu Join Date: Aug 2013 Posts: 10 Rep Power: 12	Yes, Flotus1 The percentage of viscous force is about 0.2%. But, I like to see it as totally zero. It may be because of the fact that you said. Normal vector of faces of some element are not identical to the Z axis. Thus, viscous forces on that surface produce components in Z-axis. Right? So, we should not take account that viscous force, Right? Thank you very much, Flotus1. Tunlu