CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Main CFD Forum

Alternative boundary treatment on cell-centered scheme

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   July 3, 2013, 10:12
Default Alternative boundary treatment on cell-centered scheme
  #1
Member
 
Dokeun, Hwang
Join Date: Apr 2010
Posts: 71
Rep Power: 7
dokeun is on a distinguished road
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?
dokeun is offline   Reply With Quote

Old   July 3, 2013, 11:35
Default
  #2
Senior Member
 
Filippo Maria Denaro
Join Date: Jul 2010
Posts: 1,612
Rep Power: 23
FMDenaro will become famous soon enough
Quote:
Originally Posted by dokeun View Post
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?

In a FV method is quite natural to prescribe the flux at a boundary. FOr example

mass:
zero flux on a not-permeable wall, prescribed flow rate on inflow, etc

momentum:
zero convective flux a not-permeable 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/dy|wall -> mu * (u(wall+1) - u(wall-1))/(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 ...
FMDenaro is offline   Reply With Quote

Old   July 11, 2013, 09:59
Default
  #3
Member
 
Dokeun, Hwang
Join Date: Apr 2010
Posts: 71
Rep Power: 7
dokeun is on a distinguished road
Quote:
Originally Posted by FMDenaro View Post
In a FV method is quite natural to prescribe the flux at a boundary. FOr example

mass:
zero flux on a not-permeable wall, prescribed flow rate on inflow, etc

momentum:
zero convective flux a not-permeable 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/dy|wall -> mu * (u(wall+1) - u(wall-1))/(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 ...
Dear FMDenaro.

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:
Supersonic inlet [gradients are zero]
  • Inviscid flux \rightarrow directly obtained on boundary
  • Viscous flux \rightarrow needs only care about heat conduction terms, k \frac{\partial T}{\partial x_i}
Supersonic outlet[gradients are zero]
  • Inviscid flux \rightarrow directly obtained on boundary
  • Viscous flux \rightarrow needs only care about heat conduction terms, k \frac{\partial T}{\partial x_i}
Inviscid wall
  • Inviscid flux \rightarrow need only care about pressure\left( p_w \right) at wall
Viscous wall
  • Viscous flux \rightarrow needs only care about heat conduction terms, k \frac{\partial T}{\partial  x_i}
Subsonic inlet
  • Inviscid flux \rightarrow use (*)
  • Viscous flux \rightarrow ??
Subsonic outlet
  • Inviscid flux \rightarrow use (*)
  • Viscous flux \rightarrow ??
(*)'Three-Dimensional Unsteady Euler Equations Solution Using Flux vector Splitting'. AIAA Paper 84-1552
I have no idea how can I dealing Viscous flux for subsonic inlet/outlet.

How can I implement viscous flux for subsonic boundary condition?

Thank you in advance
dokeun is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solution Diverging with Trimmer Mesh rietuk STAR-CCM+ 8 February 27, 2013 05:50
Import problem ARC Open Source Meshers: Gmsh, Netgen, CGNS, ... 0 February 27, 2010 11:56
Cell check and Boundary check errors AB CD-adapco 4 October 28, 2004 13:04
Node centered and cell centered. Confused. Main CFD Forum 9 August 29, 2003 13:54
Mac Cormack scheme and use of PML boundary conditi vineet kshirsagar Main CFD Forum 1 January 13, 2002 02:46


All times are GMT -4. The time now is 01:13.