# 3D simulation with blended wingbody. Lift a 1/3 of what it shuld be. Any wrong?

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 July 26, 2011, 08:21 #21 Member   s.rasoul_varedi Join Date: Feb 2010 Posts: 82 Rep Power: 7 why there is difference between patchIntegrate results and the results of forces due to added force function in controlDict??? i was confused??? why this happened? can every one explained briefly why the resuls is different???

 July 26, 2011, 17:25 #22 New Member   Join Date: Mar 2011 Posts: 17 Rep Power: 7 Forces calculates forces in Newtons patchIntegrate integrates the chosen field over a chosen patch. if your case uses P/rho instead of just plain P, you will have a 1/rho difference between results.

 September 12, 2011, 17:29 I found the wrong om my simulation ... #23 Member   Rickard Hidefjäll Join Date: Jun 2009 Location: Uppsala, Sweden Posts: 39 Rep Power: 9 Itś so simple that I was traped by my own expectation. The explanation is that the cl factor is less then you have a short wingspan. For a example: I did a setup with a 10 meter wingspan and a length on 1 meter. and a naca 0009. (seen from above). And 6 degree of angel of attack, 30 m/s. And got cl=0.398105. When I scaled down to a 10:th i.e. 1 meter span and a length of 1 meter I got 0.1271. After that I scaled down to a span 1 meter an a length of 0.1 meter and got a cl= 0.38623. That is exactly correct according to a Nasa full scale wind tunnel measuring. This was some thing i already known but forgot, because I experted a high drag an a slighter higher lift according to the vortex on the wing, which Ì sort of did according to the square meter wing, when I got cl=0.21 for my wing . Prismatic layer did`n change a bit.. I tried a lot of different values. And blockmesh is much better than netgen. At least in my cases. With netgen I could not simulate a wing with less angel of attack than 5 degree. There was no limit according to blockMesh. Regards / Rickard

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