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Fluids

Help running long transient simulation with solar ray tracing.

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    • TryingMyBest1232
      Subscriber

      Hello,

      I've been trying to run a transient simulation that uses Fluent's solar ray tracing that needs to be run for a few days. Unfortunately, after the first 24 hours, the sun doesn't rise again and the solar flux remains 0 forever. Can anyone give me any help or advice with this?

      I tried to run the first 24 hours, then set the time in the solar calculator to 00:00 and run the next 24 hours of the simulation without re-initialising but this only seemed to use the right sun direction vector for 1 time-step (unless I did something stupid).

      I'm quite new to fluent so sorry if this is something easy. If not, a work-around would be highly appreciated.

      Thanks

    • Rob
      Ansys Employee
      You'll need to reset the solar load for the new time as it's not designed to be run over many hours.
    • TryingMyBest1232
      Subscriber
      This is what I tried doing. After 24 hours I stopped the simulation and set the time in the solar calculator to 00:00 and then clicked apply. When I restarted the simulation it worked for one iteration but then the solar load never changed. Did I do something wrong?
    • Rob
      Ansys Employee
      Try 00:01 and see. Given it's dark I'm not sure what the solar calculator will do.
    • TryingMyBest1232
      Subscriber
      I have just tried this and I also reset the flow time to 0 to see if this would fix the issue but I'm not having any luck. I'm sure I'm just making a silly mistake but nothing I try seems to be working.
    • DrAmine
      Ansys Employee
      CAn you a try a dummy run with very large time step size just to control the solar load properties and whether the sun goes up in large time intervals.
    • DrAmine
      Ansys Employee
      What about running following test: From the time in your day run till the end of the day. Then start the second run with the new day and time 00:01 (new session, reading case and store d data).

    • DrAmine
      Ansys Employee
      The flow time might be required to bet setup back to zero!
    • TryingMyBest1232
      Subscriber
      I did some testing as suggested and found the method I was using didn't work with a 150s timestep but did with a 180s timestep. Very weird! For those with similar issues the process is:
      Run day 1
      Set solar calculator to 00:00 and apply
      Reset flow time in console with (rpsetvar 'flow-time 0)
      Run the next 24Hrs of simulation and repeat
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