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July 3, 2013, 10:12 
Alternative boundary treatment on cellcentered scheme

#1 
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Dokeun, Hwang
Join Date: Apr 2010
Posts: 71
Rep Power: 9 
Dear all
I used ghost cell concept for euler solver but confused how can I compute gradient of flow properties at boundary face for viscous flux. Because I need gradients of velocity and Temperature at ghost cell for face centered properties, but I have no idea about this. For your understanding I'd like to use modified gradient described in Blazek's Is there any alternative or breakthrough? 

July 3, 2013, 11:35 

#2  
Senior Member
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 3,084
Rep Power: 36 
Quote:
In a FV method is quite natural to prescribe the flux at a boundary. FOr example mass: zero flux on a notpermeable wall, prescribed flow rate on inflow, etc momentum: zero convective flux a notpermeable wall, prescribed flux for fixed flow rate. The diffusive flux is imposed such that the velocity on a boundary is prescribed, for example, at first order, a normal derivatives of the velocity on a wall is mu*du/dywall > mu * (u(wall+1)  u(wall1))/(2*dy) = mu*u(wall+1)/dy temperature: quite natural if you have adiabatic or fixed heat flux q = k*Grad T and so on ... 

July 11, 2013, 09:59 

#3  
Member
Dokeun, Hwang
Join Date: Apr 2010
Posts: 71
Rep Power: 9 
Quote:
Thank you for your kind reply with example. I guess I understood your explanation. But I'd like to be checked the thought below and get some more about boundary condition. Quote:
How can I implement viscous flux for subsonic boundary condition? Thank you in advance 

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