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Mechstud June 21, 2007 04:50

torque calculations
 
Hi ..

I am working on a simulation of a crop harvesting machine and I want to draw a contour plot of the torque acting on the blade due to fluid. For this I need magnitude of the torque acting on different points of the blade surface.

I used the torque function in CFX post..

torque_z@Rot Blade 1

But this function calculates the total magnitude of the torque acting on the whole blade ..not on discrete infinitesimal points of the blade..please help me to calculate torque on various points of the blade.

Thanks in advance

Mechstud

Glenn Horrocks June 21, 2007 18:44

Re: torque calculations
 
Hi,

You could write a CEL function which takes the torque component out of the pressure and wall shear variables, and does a cross product with the rotation axis.

Or you could just do contour plots of pressure and/or wall shear on the blade. No need for CEL functions then.

Glenn Horrocks

Mechstud June 22, 2007 02:40

Re: torque calculations
 
Thank you very much Glenn...

Although I have also figured out the solution to this problem 2 hurs later I posted this topic.

I defined variable which calculate torque on a point using forces in x and y direction multiplying with y and x respectively.

and then doing vector addition.

..Well in your solution ..what do you mean by wall shear variables ??..I am a bit new to CFX ..

Thanks a lot for your help once again

Best Wishes ...Mechstud


Glenn Horrocks June 24, 2007 21:50

What is wall shear?
 
Hi,

Fluid transfers momentum to a surface by two means. The first is by pressure and the second is by friction, that is shear in the fluid boundary layer. In CFX they are expressed as two separate variables, pressure and wall shear.

Glenn Horrocks

Mechstud June 26, 2007 08:53

Re: What is wall shear?
 
thanx....its all clear now...

mechstud


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