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-   -   How to calculte \Delta t from CFL? (http://www.cfd-online.com/Forums/main/8859-how-calculte-delta-t-cfl.html)

Annie March 15, 2005 18:37

How to calculte \Delta t from CFL?
 
Suppose the differential equation is a pure advection equation,

\fraction{\partial C}{\partial t} = u \fraction{\partial C}{\partial x}

And suppose CFL number is known, how to calculate time step \Delta t?

Thanks a lot.

Annie

agg March 15, 2005 19:52

Re: How to calculte \Delta t from CFL?
 
\Delta t = CFL* \Delta x

--------------

u

florin March 18, 2005 03:12

Re: How to calculte \Delta t from CFL?
 
For pure advection equation, the time step will be calculate from next relation: Dt=CFL*(Dx/u) where Dt is time step, Dx is spatial step, 0<CFL<1.

Yousuf March 23, 2005 09:05

How to Calculate Delta t for Incompressible prob?
 
In Compressible Flow Problem We calculate the Time step Value Using CFL Correlation. But in Incompressible Flow Problem How we calculate the Time step?.. What is the Physics Behind that?..

Thanks.... Yousuf

Tom March 23, 2005 10:48

Re: How to Calculate Delta t for Incompressible pr
 
If the flow is inviscid or you're using an explicit time integration scheme it is calculated exactly the same way in compressible and incompressible flows. The material derivative is a hyperbolic operator which implies a CFL restriction.


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