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Old   February 10, 2004, 08:07
Default Hey, fluent doesnt work !
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Hello: I work with sails, and i use it as parachute. I think in this case all the force over the surface must be from viscous terms ( no too much ciculation arround the sail appear), but when i make a force report the viscous force is very smaller than the pressure force. Does anyone knows why?

Other problem is that the pressure force on the sail and the sail shadow are of the same direction, and i think they must pe opossite.

When this problem appear i put a wall in a down stream inviscid flow, and the Dalambert paradox doesnt appear, There was force!. There are too many things i dont understand. Can anyone help me please?


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Old   February 10, 2004, 09:55
Default Re: Hey, fluent doesnt work !
Jonas Larsson
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On a parachute the pressure force is certainly several orders of magnitude larger than the viscous force... the code seems to be right.

Viscous forces are only dominating in cases where you have symmetric streamlined bodies without any separation. Note that the bodies need to be symmetric also, otherwise viscosity (or numerical viscosity if you use an inviscid solver) will always setup circulation which in turn generates pressure forces.
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Old   February 10, 2004, 15:17
Default Re: Hey, fluent doesnt work !
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Too much thanks.

Ive been studing the problem and with your contribution, im afraid i solve the stuff.
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Old   March 11, 2004, 10:56
Default Re: Hey, fluent doesnt work !
yogesh and amit
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hi, this is because in an inviscid solver, we use numerical viscosity of a very low value. we also encountered this problem while analysing the inviscid flow over airfoils..... we have made a 1d nozzle flow analyser and working on a 2d airfoil analysis code...that gives the Cp curves and Cd,Cl too. we want to know the the best scheme.and some references too.

we are sophomores from india.
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