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rasool motamedi May 19, 2013 06:52

courant number
I am simulating a rotating blade and it is transient.
min mesh size is 5 micro meter
max mesh size is 20 micro meter
my blade rotate 600 rpm
inlet velocity is 13333 micro meter per secound
how can define below things:

1-min and max courant number
2-best time step

is max courant number=0.2 good?
and dt=0.00001 good?
thanks regards

ghorrocks May 19, 2013 07:24

Courant number is not relevant for CFX as it is an implicit solver. I do not recommend using it to set time step size. For most transient simulations in CFX the best way to control the time step size is using adaptive time steps, homing in on 3-5 coeff loops per iteration.

rasool motamedi May 19, 2013 07:37

so Why in solver control when I active secound order backward I can define min and max courant number?

ghorrocks May 19, 2013 07:49

Just because an option is available does not mean it is a good idea to use it.

JuPa May 19, 2013 11:52

This is a good read:

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