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Bounecer June 25, 2006 12:21

airfoil boundary condition
 
hello all; I'm writing a computer code simulating flow about an airfoil, in case of 2D, incompressible, laminar and viscous flow.Reynolds number equal 2x10**3. Governing equations were adimentionalised by setting U=u/ue and V=v/ue, .......(ue is the upstream velocity) My question is about the boundary condition at upstream, is it U=1, or U=Re*visc/C Re: Reynolds number Vis: Kinematic vicosity of air C: Corde

Thanx

ganesh June 25, 2006 23:39

Re: airfoil boundary condition
 
Dear Bouencer,

The upstream BC should be U = ue/ue = 1. The kinematic viscosity would then become Vis/Re, after non-dimensionalisation.

Regards,

Ganesh

Dominic June 26, 2006 10:27

Re: airfoil boundary condition
 
Yes,

Ganesh is right. Also, to add more :

u said:

" is it U=1, or U=Re*visc/C"

It should be u=Re*visc/C and not 'U'. Here 'u' has dimensions. But U doesnt have. If u calculate 'u' based on the above Re and divide by ue, u shud get '1' at the upstream.

regards,

Dominic


Bounecer June 26, 2006 14:29

Re: airfoil boundary condition
 
Thanx Ganesh, Please i've an other question: I'm using C-grid generation, so the upstream side in physical domain become the top side in computational domain, how to write the boundary condition U=1 (condition in physical domain in terms of cartesian coordinates) in computational domain where i must express U in terms of the new curvillinear coordinates ksi and eta

Dominic June 26, 2006 23:43

Re: airfoil boundary condition
 
Hi,

If U' represents the solution in computational domain, and U in the physical domain then,

U' = [T] U, Where [T] = | d(x,y)/d(ksi,eta) |

T(1,1)=dx/dksi ; T(1,2)=dy/dksi ; T(2,1)=dx/deta; T(2,2)=dy/deta;

Here [T] is the Jacobian of the transformation..

Knowing U, you can compute U'...

regards, Dominic


Bounecer June 27, 2006 05:17

Re: airfoil boundary condition
 
thanx Dominic; If y're agree i'll send you the mathematical model in cartesian and curvillinear coordinates with descriptions, the finite volumes steps discretization and my code program in Fortran.

imah April 12, 2012 12:06

iii
 
hai all.. im also writting computer code using fortran.. i try to simulate airfoil in c-grid.. my problem is.. i not sure the boundary condition at double connected grid (after the trailing edge).. hope u all can help me.. thanks.. :confused:


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