8 Replies Latest reply on Jul 18, 2017 10:16 AM by Amin Faegh

    thermodynamic parameters in flow simulation

    Amin Faegh

      There is an option in flow simulation wizard(initial conditions) to enter your desirable temperature and pressure which I believe they are initial conditions. There are also temp and pressure options when you want to define your boundary conditions for both opening flow and and opening pressure. I am a bit confused about how to use them correctly. Can someone explain them to me please?

        • Re: thermodynamic parameters in flow simulation
          Amit Katz

          The first set of parameters you mentioned, the initial conditions, will apply to all fluid cells in your domain at the start of the simulation.

           

          The parameters for boundary conditions can be set independently from the initial conditions. If you do not set them, they will default to the values set in the initial conditions. I hope this clarifies the issue for you.

          • Re: thermodynamic parameters in flow simulation
            Amit Katz

            In that case I would use a pressure inlet boundary condition instead of a flow rate condition.

              • Re: thermodynamic parameters in flow simulation
                Amin Faegh

                Thanks Amit. Can you clarify something for me please? Are these thermodynamic parameters (temp and pressure) that already  exist in boundary condition for both flow openings and pressure openings options, initial conditions or boundary conditions? I attached a pic that shows what I mean. My other question is what if I want to have a 100 degree centigrade air flows into cylinder?BC.JPG

                  • Re: thermodynamic parameters in flow simulation
                    Amit Katz

                    They define the flow in your boundary conditions, so they are boundary conditions. I don't see where the confusion is.

                    By the way all of this information can be found in the on-line help for the software as well:

                    Specifying Thermodynamic Parameters

                    The pressure and temperature can be specified for Pressure Openings and inlet Flow Openings as follows:

                    • Static Pressure , Total Pressure or Environment Pressure can be specified for Pressure Openings.
                      The Environment Pressure condition is interpreted by Flow Simulation as a total pressure for inlet flows and as a static pressure for outlet flows. If in the course of calculation a vortex crosses an opening with the Environment pressure condition specified, this pressure is considered as the total pressure for the part of opening through which the flow enters the model and as the static pressure for the part of opening through which the flow leaves the model.

                    Additionally, if High Mach number flow is considered (see High Mach Number Flows), you need to specify the fluid Approximate Pressure for inlet Flow Openings. See Boundary Conditions in Gas Analyses for the explanation of the Approximate Pressure parameter.

                    • Pressure potential
                    • If Rotation is enabled in the Analysis Type dialog box of the Wizard or General Settings, you can select the Pressure potential check box.
                      When the Pressure potential check box is selected, the specified static pressure is considered as relative to the rotating reference frame (Pr) and the absolute pressure (Pabs) is determined through the density, angular velocity and the radius from the following formula:

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                    When the Pressure potential check box is not selected, the specified static pressure is considered as relative to the absolute frame of reference (Pabs).

                    • Temperature

                    Allows you to specify fluid temperature for Pressure Openings and inlet Flow Openings.

                      • Re: thermodynamic parameters in flow simulation
                        Amin Faegh

                        If I am interested in fluid temperature at outlet, how should I set up it then? The inlet is 0.0001 kg/s flow rate with 100 degree centigrade air flows in the pipe with 3 MPa pressure and the outlet is an opening pressure and as a default it already has 20.05 degree centigrade in there as a boundary condition. The thing is I want the software to calculate the fluid temperature at outlet, but the outlet already set to 20 degree centigrade. How does it work then? Thanks.

                  • Re: thermodynamic parameters in flow simulation
                    Amit Katz

                    You could try setting your input BC as an static pressure BC with a given temp, and set your outlet BC as mass flow rate. That should allow the software to properly calculate the heat transfer and outlet temperature without imposing the environmental condition.