|
[Sponsors] |
October 12, 2004, 11:39 |
CFL condition
|
#1 |
Guest
Posts: n/a
|
In the Anderson's Book of CFD, there is a CFL condition for the problem of supersonic flow over a flat plate. There, he use MacCormack explicit in a time-dependent approach.
My problem is I've got a coordinate transformation, x=x(xi,eta), y=y(xi,eta), so that I don't know what to write instead of \Delta x and \Delta y in the CFL condition. Thanks in advance. |
|
October 13, 2004, 09:47 |
Re: CFL condition
|
#2 |
Guest
Posts: n/a
|
Many papers have answers. Let \xi_X and \xi_Y be metrics of corrd. transformation, in a illustrative way, D t= CFL /( |u * \xi_X +v * \xi_Y| + C * sqrt( xi_X**2 +xi_Y**2)). where C is sound speed. Note that the dimenson is consistent with definition of CFL number. One can similarly get Dt from another direction \eta. The minimum of the two is what desired.
|
|
October 13, 2004, 16:38 |
Re: CFL condition
|
#3 |
Guest
Posts: n/a
|
Thanks versi, very useful! I will try that.
I've got another question. If x=x(nxi,neta); y=y(nxi,neta); XI=XI(nxi,neta); ETA=ETA(nxi,neta); Could you confirm that the next sentence is calcutating the metrics? XI_x=zeros(nxi,neta); ETA_x=zeros(nxi,neta); XI_y=zeros(nxi,neta); ETA_y=zeros(nxi,neta); for i=2:nxi-1; for j=2:neta-1; XI_x(i,j)=(XI(i+1,j)-XI(i-1,j))/(x(i+1,j)-x(i-1,j)); ETA_x(i,j)=(ETA(i,j+1)-ETA(i,j-1))/(x(i,j+1)-x(i,j-1)); XI_y(i,j)=(XI(i+1,j)-XI(i-1,j))/(y(i+1,j)-y(i-1,j)); ETA_y(i,j)=(ETA(i,j+1)-ETA(i,j-1))/(y(i,j+1)-y(i,j-1)); end end Thanks if you try that. |
|
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
CFL Condition | Matt Umbel | Main CFD Forum | 19 | June 30, 2020 09:20 |
CFL condition: can a mass balance problem arise if violated? | bzz77 | Main CFD Forum | 3 | August 24, 2011 16:12 |
Is CFL condition irrelevant for incompressible flow? | violet | FLUENT | 0 | November 5, 2009 18:33 |
CFL condition for higher order schemes | Shyam | Main CFD Forum | 2 | February 14, 2008 15:24 |
CFL condition for implicit CD schemes | turb | Main CFD Forum | 4 | August 16, 2005 13:56 |