Setting up a Design Study and Defining Surrogates

The pipeline junction surrogate must provide results across the range of flow conditions that are expected in the system. For this tutorial, depending on the pump operating conditions, estimated flow conditions range from zero to 720.33 kg/s in each of the three arms of the junction.

You set up a DOE design study with surrogates that match the parameters required for the 1D system simulation in Simcenter Flomaster. A DOE study using sampling method Latin Hypercube Sampling products precise surrogates.
  1. In the Design Manager project file, right-click the Design Studies node and select New.
  2. Select the Design Studies > Design Study node and set Study Type to DOE
  3. Select the DOE Settings node and set DOE Type to Latin Hypercube Sampling.
  4. Select the DOE Settings > Sampling Settings node and set Designs to Run to 100.

    The LHS algorithm combines the input parameters with each other in a way that maximizes the minimum distance between the generated design points. This algorithm promotes an even distribution of design points over the design space.

    For more details, refer to Latin Hypercube Sampling.

  5. Rename the Design Study to junction_DOE.
To add design input parameters:
  1. Select the Design Studies > junction_DOE > Input Parameters node and set Parameters to contain the following global parameters from the reference simulation:
    • Mass Flow 1
    • Mass Flow 2
    • Mass Flow 3
The pump specifications in the Flomaster 1D model suggest that the range of flowrates for the arms in the junction be defined from 0 to 720.33 kg/s. The starting value in the reference file is 360.155 kg/s. In a Latin Hypercube Sampling DOE study, the reference value has no impact on the procedure to define design runs.
  1. Select the Input Parameters > Mass Flow 1 > Continuous node and set the properties as follows:
    Property Setting
    Range [0.0,720.33] kg/s
    Baseline Value 360.155 kg/s (read only)
  2. Repeat the step above for the input parameters Mass Flow 2 and Mass Flow 3.
To add design responses:
  1. Select the Design Studies > junction_DOE > Responses node and set Responses to contain the following reports:
    • SA Total Pressure Inlet1
    • SA Total Pressure Inlet2
    • SA Total Pressure Inlet3

    The three responses correspond to the three reports in the reference simulation, where the surface averaged total pressure levels at inlets are calculated. No report is required for the outlet pressure as by definition this pressure is set to 0 Pa. Therefore, the total pressure levels represent the total pressure drop between inlet and outlet.

To add the pre-defined scenes from the reference simulation to all the design runs:
  1. Select the Design Studies > junction_DOE > Scenes node and set Scenes to contain Vector Scene Velocity.
For each response you specify a surrogate. Design Manager populates the surrogates while it runs the design study.
  1. Right-click the Design Studies > junction_DOE > Surrogates node and select New Surrogate.
  2. Rename the Surrogate node to Surrogate_SA_Total_Pressure_Inlet1 and set its properties as follows:
    Node Property Setting
    Surrogate_SA_Total_Pressure_Inlet1 Response [SA Total Pressure Inlet1]
    Kriging Tuning Precise Kriging
  3. By repeating these two steps, create surrogates for the following responses and rename them as:
    • Surrogate_SA_Total_Pressure_Inlet2
    • Surrogate_SA_Total_Pressure_Inlet3
  4. (Optional) To enable multi-editing of the created surrogates, right-click the Design Studies > junction_DOE > Surrogates node and selecting Edit Surrogate .
    The Surrogate Table is opened up for editing. See also: Edit Surrogates.
  5. Select File > Save As. In the Save dialog, set File name to junction_with Surrogates.dmprj and click Save