Center of Pressure for a pressure distribution on a curved Surface

[Xprivate]

hey everyone, i have a structure that is having a complex curvature, the curvature has some varying pressure distribution and i want to find the center of pressure for this pressure distribution. how do i do that on FEMAP. FEMAP gives me loads and moment along a requested CSYS but it doesnt give Cp for the applied load. Any suggestions , ideas? Thank you in advance

 

[rb1957]

maybe FeMap has some report on the applied load (so maybe you can get the resultant directly from FeMap). but to get it from NASTRAN ...

run the shell model. to do so, you'll need 6 constraints to remove rigid body motion.

Otherwise, the NASTRAN F06 file includes a summation of the applied load, "OLOAD" I think.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[Xprivate]

but will that OLOAD or resultant from FEMAP give the summation co-ordinates ?

 

[SWComposites]

my memory is bad, but isn't the OLOAD output relative the origin of the basic coordinate system?

 

[rb1957]

yes, OLOAD is the resultant about the origin, so you know the magnitude of the resultant and it's line of action.

but in FeMap, under Tools/Check there is "sum forces" which might do the same thing directly ?

or run in FeMap with one point constrained in 6 dof ... this'll give you the resultant about this point. if you're lucky (or clever) and the point is on the line of action, then the three moments will be zero.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[rob768]

if the model is a single surface, and assuming the pressure is uniform, isn't the center of the pressure at the center point of the surface? which can be found using the section properties of the surface?

 

[rb1957]

nonuniform pressure ? CP can be anywhere.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[rob768]

True. I misread the part about the varying pressure distribution.

 

[TG_eng]

Did run the Nastran analysis with Force Balance request? Perhaps you could create an Interface Load - Freebody using the elements on your surface.

 

[Holbewoner]

tools > check > sum forces will give you the total load, incl moments, around any chosen point. You should be able to calculate the COG from that.