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

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

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

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

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

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.

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: