fundamental question about Lift Report and Integral Pressure

farzadpourfattah · June 17, 2015, 02:56

Hello.
I simulate flow around a wing at angle of attack 0 degree and my pressure distributions is valid experiment result. BUT , when I compare lift force (Report>force>(0,1,0) ) with (Report>integral>static Pressure on wing),
I am confused! that why these value is differ together?
please help me.

Kokemoor · June 17, 2015, 10:41

The integral of pressure is a scalar, it has no direction. Integrating across the entire wing will sum together pressure contributions from all surfaces, regardless of direction.

The lift force is the pressure times the dot product of the face area vector and the direction vector you specify; pressure pushing down will cancel out with pressure pushing up, and pressure pushing to the side will not be affect the calculated force.

farzadpourfattah · June 17, 2015, 13:14

Thanks alot.You elucidate me about this.
I search in all document of Fluent software to find relation of computing lift force but I can't find,Can you guide me?

Kokemoor · June 17, 2015, 14:00

Check out the Fluent Theory Guide, Section 22.2.1. Computing Forces, Moments, and the Center of Pressure.

June 17, 2015, 02:56	fundamental question about Lift Report and Integral Pressure	#1
farzadpourfattah Member farzadpourfattah Join Date: Mar 2013 Posts: 41 Rep Power: 13	Hello. I simulate flow around a wing at angle of attack 0 degree and my pressure distributions is valid experiment result. BUT , when I compare lift force (Report>force>(0,1,0) ) with (Report>integral>static Pressure on wing), I am confused! that why these value is differ together? please help me.

June 17, 2015, 10:41		#2
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 13	The integral of pressure is a scalar, it has no direction. Integrating across the entire wing will sum together pressure contributions from all surfaces, regardless of direction. The lift force is the pressure times the dot product of the face area vector and the direction vector you specify; pressure pushing down will cancel out with pressure pushing up, and pressure pushing to the side will not be affect the calculated force. farzadpourfattah likes this.

June 17, 2015, 13:14	dear Kokemoor	#3
farzadpourfattah Member farzadpourfattah Join Date: Mar 2013 Posts: 41 Rep Power: 13	Thanks alot.You elucidate me about this. I search in all document of Fluent software to find relation of computing lift force but I can't find,Can you guide me?

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June 17, 2015, 14:00		#4
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 13	Check out the Fluent Theory Guide, Section 22.2.1. Computing Forces, Moments, and the Center of Pressure.