Adding Hoses To System Causing Large Oscillations and a Slow Model

Tyler Winquist
Tyler Winquist Altair Community Member
edited March 7 in Community Q&A

Hello,

We are running into an issue with our model when we add in hoses. The addition of the hoses causes the model to be very slow going from a couple of seconds run time to more than 20 minutes. The system also oscillates largely in terms of the system pressures - I have attached the current model bellow and I suggest opening it and running the simulation to see the issue first hand. Not sure why this is happening but we would greatly appreciate any advice to get around this issue!

Thanks,

Tyler

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Answers

  • RoKet_21298
    RoKet_21298
    Altair Employee
    edited March 7

    Hi Tyler,

    nice model!

    This is a pure numerical effect. There are two solutions (or a combination of both):

    1. Increase the volume at the ends of pipes (dead volume in pump and motor) to ~0.1 l.
      Simulation is still slow, but finishes in a reasonable time.
    2. Select another solver. With Radau-IIA the simulation takes ~ 1 s (+ time to compile if necessary).
      CPode, Cash-Karp and SDIRK deliver a similar speed.

    Regards

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