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Hello!

I am running a simulation of a system of rivers and lakes. Currently evaluating the effects of some changes in my mesh by running the simulation with a variable time-step.

The desired courant number is set to 0.8 and the maximum courant keeps well below this (<0.4). The time-step, however, never goes above 1.0000s. Is this set by a parameter? Or might there be another reason that the time-step does not increase?

Best regards

Jonas

Hello Jonas

The question is a not really clear!
When you set the desired Courant number (CFL), this will imply that telemac will compute the time-step based on that Courant number. Then Telemac will use the maximum between the time-step you have given in your steering file (1s?) and the one that verifies the CFL condition.

I hope that this helps

Riadh ATA

I have not specified a time step in the simulation when running with a variable time step. Just to make sure I understand you correctly:

DURATION = 865440
VARIABLE TIME-STEP = YES
DESIRED COURANT NUMBER = 0.8
TIME STEP = 2

Specifying this in the steering file will put the time step between 0s and 2s?(as close to 2 as possible without violating the CFL-condition)

Best regards

Jonas

Hi
In fact, 1s is the default value for time step, this is why you never have a greater time step in your first computation

So this should works with if you give 2s in your steering file.

Just an important point.The given time step is allways used to compute the first step in order to compute the first courant number and the adjust the time step accordingly

Hope this helps

Regards

if you specify a small time step it will use this all the time so I would advise using a bigger one and then the variable time step selection will kick in. Again this depends on the particular application but if 2seconds always gives a Cr less then your 0.8 the 2 seconds will be used.

regards
Tony C