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Confusion of the Courant number definition

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Old   October 17, 2007, 00:05
Default Confusion of the Courant number definition
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I think Courant number is a basic concept to many people here. In many CFD textbooks, it's defined as C=u*delta_t/delta_x, where u is the local flow velocity. But sometimes for the compressible flow simulations, people often take it as C=(u+a)*delta_t/delta_x, in which a is the local sonic speed. I am very confused about this. Can anyone give an explanation?

Thank you.
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Old   October 18, 2007, 05:14
Default Re: Confusion of the Courant number definition
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The local velocity ( velocity in each cell) equal to the max of eigenvaluse of the jacobien matrix. the eigenvaluse are forms of: (U+adiabatic sound speed),(U-adiabatic sound speed),(U). and automatically choised (U+a) because is the most great.

a=sqrt(gama*P/rou) EMCAS
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Old   October 23, 2007, 08:03
Default Re: Confusion of the Courant number definition
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this brings more confusion! let me ask another question regarding the Courant (CFL ) number which maybe helpful in going through the depth of it. you may have seen in steady computation that CFL number does still exsist. but in definition you see that CFL=Udt/dx . how can it be possible since we are in steasy mode and there might not be any Delta (t) ... time step in the other word.
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Old   December 9, 2013, 13:12
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