Fluids

Fluids

Simulation of Liquid piston

    • mamun067
      Subscriber

      I've started a simulation on the liquid piston in Ansys fluent. With a piston speed 800cc/s, the movement of the liquid piston in the upward direction is showing correctly. (Figure 2) But pressure contour at 2.7s seems incorrect but the temperature contour shows correct (Figure 3).

      My question is how to patch particular pressure and temperature correctly in the VOF model in a region ( The whole cylinder chamber is air initially)

    • Rob
      Ansys Employee
      You patch the air pressure to be whatever you want it to be. Assuming you set the air density as ideal gas it'll then compress as you force water into the domain. Why wouldn't the water be at the same pressure as the air?
    • mamun067
      Subscriber
      i need to give air to fully occupied the chamber at initial, so I patch like this. (1st figure). Then I also need to give the air at 7 bar and 310K initially so I patched like this ( 2d figure). My ques, pressure patching is correct or not?
      The ref paper said that the density of air should be 'peng Robinson' model and only the velocity of water at the inlet was mentioned. That's why i am following this...

    • Rob
      Ansys Employee
      That's a real gas model, not sure you need that but that's for you to decide. Is water then added at a fixed rate, or drawn into the system as the air cools?
    • mamun067
      Subscriber
      Yes, I have to model the air as real gas. And water is entering at the inlet at a fixed velocity of 0.176 m/s to satisfy the volumetric flow rate 800 cc/s. Could you give me a suggestion about the patch? i.e How to set the initial pressure and temperature for air region?
    • Rob
      Ansys Employee
      You use the patch function, or initialise the model at the desired temperature and pressure. In this case I'd use "standard" initialisation as hybrid won't give a sensible starting point.
      As an aside, posting into a different section of the forum with the same question tends to delay responses as we have to figure out which is the live thread and which to delete.
    • mamun067
      Subscriber
      Thanks Mr. Rob. Thanks for your suggestion about patching, now I got it. Sorry, for reposting. As a new user, I didn't know that.
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