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-   -   post processing CL values (https://www.cfd-online.com/Forums/fluent/34867-post-processing-cl-values.html)

 Joe Bryant October 18, 2004 01:48

post processing CL values

Hi, i just wanted to know if i use the Cp values from fluent and plot them against chord and find the area under the graph to calculate Cl, If i want to find the lift i know that

Cl = L / 0.5 X Rho X V^2 X S

is this S going to be half, if i have only ran half a model of the rear wing in CFD due to symmetry conditions to reduce processing time.

 Luca Cavagna October 18, 2004 03:59

Re: post processing CL values

Hi Joe, the surface you should use is not so important because it's just a reference value;anyway I sugggest using half of the area of the wing... to find the CL you should find the resultant vector and projected along the direction normal to the velocity "far field" vector. I don't know if you can do it directly with Fluent or if you have to write a UDF. Luca

 Joe Bryant October 18, 2004 04:17

Re: post processing CL values

So if i use the cp value from Fluent just straight out, only changing the ref value of velocity to the same speed at which the program was ran i.e. 40 get the corresponding Cp graph integrate it in matlab to calculate the area under the graph which is evivilant to cl then use the formula

cl= L / 1/2 rho v^s S

Where S will be (b*c /2)

If we were using the Cl and Cd values from fluent i suppose we would be placing in only half the area right?

Any thoughts would be appreciated cheers Joe

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