Setting the Initial Conditions

You specify the initial conditions in the cylinder and ports using tables. A single table describes both absolute pressure and temperature as a function of crank angle. Simcenter STAR-CCM+ In-cylinder evaluates the initial values at the specified start angle (300 deg crank angle) using linear interpolation between the data points.

For the cylinder, you import a table that is derived from experimental results. For the ports, as no experimental results are available, you approximate the initial conditions using the inlet and outlet boundary conditions, respectively.

To set initial conditions for the cylinder:
  1. Right-click the Engine > Cylinder node and select Edit.
  2. Within the Edit dialog, in the Initial Conditions tab, click Cylinder.
  3. In the Cylinder group box, set the initial Pressure using tabular data:
    1. Next to the File drop-down menu, click Import.
    2. In the Import Table dialog, navigate to the inCylinder folder of the downloaded tutorial files.
    3. Select cylinder.csv and click Open.
      In the Graphics window, a plot opens that displays the absolute pressure in the cylinder as a function of crank angle. The correct table columns and units for the pressure are assigned automatically.
  4. Set the initial Temperature:
    1. From the File drop-down menu, select the previously imported file cylinder.
    2. Set the following table properties:
      Property Setting
      Temperature Column T_K
      Temperature Units K
    The initial conditions for the cylinder are now complete. The plot in the Graphics window displays the absolute pressure and temperature curves for the cylinder:


  5. To determine the absolute pressure and temperature values that Simcenter STAR-CCM+ In-cylinder uses for initialization, hover the mouse over the respective curve and stop at 300 deg crank angle.
    The coordinates are displayed next to the pointer. The initial absolute pressure value is 1.46769 bar and the initial temperature value is 1052.57 K.
  6. Click Cylinder to minimize the group box.
To set initial conditions for the ports:
  1. Using the same procedure as described for the cylinder (Steps 2 - 5), set initial conditions for:
    • Intake Port 1 using the file intakePort1_Inlet.csv
    • Exhaust Port 1 using exhaustPort1_Outlet.csv
    The plots below display the absolute pressure and temperature curves:


    At 300 deg crank angle, the intake port pressure value is 0.97650 bar. The temperature value is 316.772 K.



    For the exhaust port, the initial absolute pressure value is 1.35256 bar and the initial temperature value is 986.679 K.

  2. Click Apply.
  3. Save the simulation .