Fluids

Fluids

Definition of Velocity Boundary Condition in Ansys CFD software – Forte

    • sridharsahoo366
      Subscriber

      In a constant volume chamber, we did 6 hole nozzle injector to simulate gas (methane) injection simulation. As part of the inlet boundary condition, we used velocity inlet boundary condition (i.e. 25m/s) for all the nozzles.

      The results obtained are so confusing

      1. The mass flow rate of each nozzle is different from the other.

      2. With the increase in injection velocity, the simulation fails stating "Recycling requested by state variable update" and fails finally saying timestep driven is too small.

      Why this phenomenon occurs.

      The constant volume chamber is closed from every side, and nitrogen is filled in the chamber.

    • Rob
      Ansys Employee
      What is the gas density and which solver are you using?
    • DrAmine
      Ansys Employee
      If the temperature at inlet is the same as well as the same absolute pressure and the same area then the mass flow rate should be same.
    • sridharsahoo366
      Subscriber
      Thank you all, DrAmine is right, I was using the isentropic density option, that's why I was getting a different mass flow rate.
    • sridharsahoo366
      Subscriber
      May be due to high pressure, the solution was not converging.
    • Karthik R
      Administrator
      Hello What are your boundary conditions? Can you share a few more details so we understand your model and, perhaps, a few screenshots of your set-up as well?
      Karthik
    • sridharsahoo366
      Subscriber
      I am injecting natural methane gas through six nozzles, variable mass flow boundary is implemented. However, at a lower mass flow rate (0.18 g.sec) the result was good but at this mass flow rate (0.43 g/s) the recycling requested by pressure iteration is coming in the log file. This will result in smaller time step and finally, simulation will be stopped. I don't know why this pressure recycle request is coming.
      Any idea will be very helpful. This work is to be implemented in natural gas direct injection engine.
    • sridharsahoo366
      Subscriber

    • sridharsahoo366
      Subscriber
    • sridharsahoo366
      Subscriber
      @Kremella, I am trying to simulate methane direct injection into a constant volume chamber. When using a variable mass flow rate of 0.43 g/s, the recycle request from pressure variable is coming. Why this error comes, this leads to stop the simulation.
    • DrAmine
      Ansys Employee
      You are using Forte?
    • sridharsahoo366
      Subscriber
      Yes, I am using Forte.
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