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CFL number

I'm working at a University where we are developing and running interface software for CFD simmulations. There are no CFD specialists in my lab, however, so we get the information we need from a couple of other labs around campus.

Unfortunately, no one seems to know what the CFL number is, or how to use it.

Can I just get a simple explanation of the CFL number and a general range in which it should lie?

Thank you! 

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See the wikipedia article http://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition

For forward Euler time integration a safe number to use is 0.5 (though higher values may also work).  

-- Biswajit 

TAND0011's picture

CFL which is also known as Courant–Friedrichs–Lewy is a condition involved in the important role of measuring the stability of unstable computational numerical methods involved in modeling of convection or wave phenomena.  Effectively, the CFL condition helps to clearly express the net distance that any information travels during the timestep length within the mesh must be lower than the distance between mesh elements. This means that information from a given cell or mesh element must propagate only to its immediately adjacent neighbors.

From my experience, the solver must be able to keep the maximum Courant number around 0.5 in order for the simulation to converge nicely. 

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