Analyzing the Results in GT-POST

Using GT-POST, you analyze the results of the GT-SUITE simulation. You can determine the number of cycles that are required to reach a steady state solution, and visualize the converged values for pressure, temperature, and mass fractions. These values can be used as initial conditions in Simcenter STAR-CCM+, in order to speed up convergence of the co-simulation.

NoteThe initial conditions in Simcenter STAR-CCM+ do not need to match the GT-SUITE results exactly, as the influence of the initial conditions reduces during the transient solution. However, a close approximation speeds up convergence during the first few time-steps.

To launch GT-POST:

  1. In the Run ribbon, click View Results.


  2. In the Open dialog, select CFDCoupling_Setup.glx and click Open.
To visualize the number of cycles that are required to reach a steady state solution:
  1. In the Results File ribbon, make sure that Tree Pane is selected.


  2. In the tree pane, select the TimeRLT tab.
  3. Right-click the EngineCrankTrain > engine > Performance > BMEP plot and select View.


    The simulation reaches a periodic steady state solution after 17 cycles. Therefore, when running the co-simulation, you allow GT-SUITE to run 20 pre-cycles before sending data to Simcenter STAR-CCM+.

To visualize the pressure results:

  1. In the menu bar, select the Macros tab.
  2. In the Plot Macros ribbon, click RLT Plots.


  3. In the Run RLT Macro dialog, select Time RLT and click Next.
  4. In the Data tab, select the Plot1, X cell.
  5. In the RLT Selection group box, select the RLT tree > Special node and select the Cycle Number data.
  6. In the Data tab, select the Plot1, Y1 cell.
  7. In the RLT Selection group box, select the RLT tree > main > Components > FlowSplitTRight > InMan01 > Pressure node, and select the Pressure at End of Cycle data.
  8. Repeat the above steps and select the following data for the remaining components.
    Cell Node Data
    Y2 FlowSplitTRight > InMan02 > Pressure Pressure at End of Cycle
    Y3 FlowSplitTRight > InMan03 > Pressure Pressure at End of Cycle
    Y4 FlowSplitTRight > InMan04 > Pressure Pressure at End of Cycle
    Y5 FlowSplitGeneral > egr-fs-cfd > Pressure Pressure at End of Cycle
    Y6 PipeRound > InPipe-cfd > Pressure Pressure at End of Cycle (Outlet)


  9. Click Next.
  10. In the Dataset Labeling box, delete the existing text, enter [PARTNAME], and click Finish.
    When complete, GT-POST displays the following plot, which shows that pressure is approximately 2.13 bar.

Use a similar procedure to visualize temperature:
  1. Set the x- and y-axis data for the RLT plot as summarized below:
    Cell Node Data
    X RLT tree > Special Cycle Number
    Y1 FlowSplitTRight > InMan01 > Thermal Temperature at End of Cycle
    Y2 FlowSplitTRight > InMan02 > Thermal Temperature at End of Cycle
    Y3 FlowSplitTRight > InMan03 > Thermal Temperature at End of Cycle
    Y4 FlowSplitTRight > InMan04 > Thermal Temperature at End of Cycle
    Y5 FlowSplitGeneral > egr-fs-cfd > Thermal Temperature at End of Cycle
    Y6 PipeRound > InPipe-cfd > Thermal Temperature at End of Cycle (Outlet)
To visualize the species mass fractions:
  1. Select the TimeRLT tab.
  2. Right-click the main > CONTROL > SpeciesSampler > Cylinder_Runner_1 > Main > n2-vap Mass Fraction node and select View.

    When complete, GT-POST shows that the initial n2-vap mass fraction is approximately 0.60.

  3. Repeat the above procedure for each gas component, to visualize the remaining mass fractions.
    Trace components (<1%) are not included in the initial composition. All trace components are included in the n2-vap mass fraction, as it is the largest of the gas components and the total mass fraction must equal 1.
    The mass fractions are summarized in the table below:
    Gas Component Mass Fraction
    n2-vap (Fresh Nitrogen) 0.601
    o2-vap (Fresh Oxygen) 0.183
    prod_n2 (Burnt Nitrogen) 0.154
    prod_co2 (Carbon Dioxide Products) 0.043
    prod_h2o (Water Products) 0.016
    prod_o2 (Burnt Oxygen) 0.001
  4. Close GT-POST.