Where to set the required time steps to run through the speed ramp up?

Torben Henrich
Torben Henrich Altair Community Member
edited June 7 in Community Q&A

Hi,
I would like to perform a CFD topology optimization. In order for the results to converge faster, according to support it is advisable to first perform a topology optimization at low velocity (already done) and then use the result as initial design topology for the second optimization run with higher inlet velocity.
To do this, I now introduce a velocity ramp up, starting with the velocity of the first optimization run and going up to the target velocity (see image).

image

My question:
Where do I have to increase the time steps in order to completely run through the piecewise linear velocity progression (prevent the calculation from aborting before reaching the maximum inlet velocity due to reaching the convergence criterion).

1. in the flow solution via the “maximum no. of time steps”, or
2. in the optimization via the “minimum no. of design iterations”

As the simulation takes a long time, I don't want to have to test it first.

Many thanks and best regards,

Torben

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Answers

  • Sagaya Prasanna Kumar Savarimuthu
    Sagaya Prasanna Kumar Savarimuthu
    Altair Employee
    edited June 6

    Hi Torben,

    Use the "Maximum no. of time steps" in the solver settings of the Flow solution setup for your requirement.

    Notice that for each iteration of the optimization solution, the flow solution will have to run for 1000 time steps. Usually AcuSolve will converge for a given set of BCs within 100 iterations max. So, you can reduce some time by running it for 800 time steps instead of 1000. Give it a try and see if helps you.

  • Torben Henrich
    Torben Henrich Altair Community Member
    edited June 7
    Sagaya Prasanna Kumar Savarimuthu said:

    Hi Torben,

    Use the "Maximum no. of time steps" in the solver settings of the Flow solution setup for your requirement.

    Notice that for each iteration of the optimization solution, the flow solution will have to run for 1000 time steps. Usually AcuSolve will converge for a given set of BCs within 100 iterations max. So, you can reduce some time by running it for 800 time steps instead of 1000. Give it a try and see if helps you.

    Hi Sagaya,

    Thank you very much for your help. I have reduced the number of time steps to 800 and carried out the optimization. It has worked.

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