Setting Boundary Conditions

You define the boundary types and specify the appropriate property values. Set the boundary conditions for the inlet, outlet, and pipe wall.

To set the boundary conditions:

  1. Expand the Regions > Tube_2D > Boundaries node to reveal the different boundaries.

Start with the Inlet boundary conditions. The inlet temperature is 273.1 K and the volume fraction is 1.0.

The dynamic pressure and contribution to stresses due to turbulence are removed from the specified pressure at a pressure outlet in case of reverse flow. The inlet pressure profile is therefore specified as: 1.0+12ρu2 as specified in the Inlet Pressure field function. This setting is to make sure that the static inlet pressure is always effectively 1.0 Pa when water flows into the pipe.

  1. Edit the Inlet > Physics Values node and set the following properties:
    Node Property Setting
    Pressure Method Field Function
    Scalar Function Inlet Pressure
    Static Temperature Value 273.1 K
    Volume Fraction Value [1.0]


The outlet pressure is set to atmospheric pressure, that is, 0 Pa gauge pressure. However, a field function is already defined for outlet pressure in the previous section and is reused here. The advantage of this method is: if you must change the pressure profile across the whole domain, you alter the outlet pressure value in only one place, rather than two.

  1. Edit the Outlet > Physics Values node and set the following properties:
    Node Property Setting
    Pressure Method Field Function
    Scalar Function Outlet Pressure
    Static Temperature Value 273.1 K
    Volume Fraction Value [1.0]

Specify the freezing wall boundary conditions.

  1. Create the following field function using the same procedure as in the previous sections.

    Node Title

    Wall Temperature

    Dimensions

    Temperature

    Function Name

    WallTemperature

    Definition

    min(273.1, 2010.0*pow($${Position}[0] - 0.15, 2) + 253.0)

  2. Edit the Wall boundary and set the following properties:
    Node Property Setting
    Physics Conditions > Thermal Specification Condition Temperature
    Physics Values > Static Temperature Method Field Function
    Scalar Function Wall Temperature


    Simcenter STAR-CCM+ applies a no-slip boundary condition to a wall by default, which is what is required in this simulation.

  3. Save the simulation.