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Defining area value in CFX-post

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Old   January 16, 2020, 09:36
Default Defining area value in CFX-post
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Hello all,
I am trying to create a chart in CFX-post that will display the drag coefficient. I've created an expression to determine the drag coefficient:
(2*force_x()@airflowdomain )/ (AR*den*(InletVel)^2)
where AR is the surface area of the object in question and den is the fluid density. However, the value being returned is a Cd of 0.0038, which seems very very low.It seems to me there must be a mistake I've made in determining the force being exerted over the front of the object, but I'm not sure where.
Any suggestions/advice would be greatly appreciated!

Last edited by itb7; January 16, 2020 at 11:26. Reason: clarifying issue
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Old   January 12, 2021, 23:25
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There seems to be an error in your equation.

If the velocity is aligned with the x-axis, you could obtain the drag coefficient as Cd = force_x()@Surface / (0.5*Rho*U^2*A)

There is also a thread that you could go through to troubleshoot your issue(s);
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Old   January 13, 2021, 11:54
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1.) As aero_head states: location for force_x() should be the surface object in question, not the domain.
2.) "AR" should not be the surface area, but instead the cross sectional area normal to the flow direction.
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cfx-post, drag coefficient, expressions, variable definition

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