Center of Force in Wall Calculator

[erickdsmith]

I'm having problems figuring out the center of force results from the wall calculator.Below is the summary output, when I compare the center of force figures to the design they don't add up. Also i don't know what the second column of numbers in the summary output are.

Note1: The results are only for the model surfaces and exclude the surrounding box.

Note2: there is an X offset of -0.4889 m  and no Y offset between the model and the environment box created in Sim CFD.

CSV output table:

 

[erickdsmith]

Anyone?

[srhusain]

With regard to the 2nd column, take for example the center of force about the Y axis- which display the X (1st column) and Z (second column) coordinate of an axis normal to the X-Z plane about which the total moment vector is zero.

I am not sure what you mean by the centers of force not adding up- can you expand upon it a bit more?

[erickdsmith]

I'm sure the problem is that I'm not familiar with a convention or something.

When I said the centers of force don't add up, I meant comparing the numerical output to the view of the object, the CoF seems wrong. i.e. the output says the CoF is at (0, -0.43, -0.46) but looking at the object, the center of mass seems to be somewhere around (0.92, 1.16, z) where the center of force should be close to.

[srhusain]

The center of force has nothing to do with center of mass because the forces acting on the body due to the fluid is separate from any gravitational forces which do act through its center of mass.

[erickdsmith]

Doesn't the center of the force have to be somewhere on/in the body?

[srhusain]

No. consider a thin sail under the action of wind.

[nhahn · Accepted solution]

Force center offset from the axis is a way to communicate the moments on a part, in addition to the forces, without having to define a particular axis for the moments.

Think of the force center as where you would need to apply the force in that direction to cause the residual moment to be zero in a free body diagram.

For example, in 2D, if the force due to pressure was 1N in the X direction, and the moment due to the uneven pressure distribution about the Z axis was 10 N*m, then the force center would be at Y=10.