Map convective results

Learn how to extract fluid temperature and heat transfer coefficient (HTC) results from a 2D Whole Engine Model and map them to a 3D submodel.

Download and extract the part files.

Introduction

A common workflow in gas turbine design is to create detailed submodels that use results from the 2D Whole Engine Model (WEM) as boundary conditions. This approach is necessary when components exhibit asymmetric thermal behavior or include non-axisymmetric geometric features—for example, blade roots on disks or exhaust assemblies. Mapping convective boundary conditions allows designers to capture more realistic thermal gradients, leading to improved accuracy in life and durability predictions.

In this tutorial you will:

  • Map fluid temperature and heat transfer coefficient (HTC) from 2D to 3D.
  • Create Result Probe to extract HTC on face.
  • Create Field from Results.
  • Apply fields on 3D cyclic geometry.

Load the 2D model and inspect thermal boundary conditions

Review applied streams, convective zones, and overlapping boundary conditions prior to extracting results.

  1. Choose File→Open and open convective_results/2D/strut_sim1.sim.
  2. Inspect applied thermal streams in the ST folder and thermal convective zones in the CZ folder.
  3. Observe that the CZ2_FACE and ST10 boundary conditions overlap on the same face.
  4. Confirm that CZ2_FACE uses an HTC of 300 W/m²K, when SCALER=1, and ST10 side A uses an HTC of 15 W/m²K, when SCALER=1.

Solve the 2D model and inspect convection results

Solve the transient 2D model and evaluate convection coefficient results, including behavior at regions with overlapping boundary conditions.

  1. Solve the Convective_Transient solution.
  2. In the Post Processing Navigator, display the Convection Coefficient - Elemental result of the last increment.
  3. Under Post View, display only 2d_mesh(3), 2d_mesh(4), 2d_mesh(5), 2d_mesh(6), and 2d_mesh(7).
  4. Use the Identify Results command to inspect the temperature on the 4391 element.


    Verify that the value is 315 W/m²K, which represents the sum of the heat transfer coefficients from the overlapping boundary conditions. Understanding this behavior is important, as it limits what data can be directly mapped to the 3D thermal model. For this region, the boundary conditions will be handled differently in the 3D model.
  5. Under Post View, display solver-created 1D elements to observe available convective results on edges.


Create result probe to extract HTC from a face

Create a result variable and probe to extract convection coefficient data from strut faces for mapping to the 3D model. The Result Probes command provides an automated method for extracting result fields from the analysis. Because the 3D model contains repeating cyclic sectors, an axisymmetric field will be used to ensure the mapped results are applied consistently across all sectors.

  1. Choose Results > Manipulation > Result Variables to create result variables with the following settings:
    • Name = HTC
    • Result Type = Convection Coefficient
    • Coordinate System = Absolute Rectangular
  2. Choose Results > Manipulation > Result Probe to create result probes on the faces of the strut referencing the HTC variable. Set the following settings:
    • Name = HTC_STRUT_FACE
    • Formula = HTC
    • Load Case = Ignore
    • Selection Type = Faces

    • Result Type = Convection Coefficient
    • Unit = W/m2°C
    • Output Options = Field
    • Independent Domain = 3-D
    • Time, Axisymmetric Plane
    • Select the Create Output check box to automatically generate a field from the result probe

    Verify that a corresponding field appears under Fields in the Simulation Navigator.

Create a field from results to extract fluid temperature on face

Extract the fluid temperature in post-processing by creating a field from the displayed results. Use this method when you cannot extract certain quantities—such as Total Absolute Fluid Temperature at the wall—with result probes.

  1. Display Total Absolute Fluid Temperature on Walls – Nodal of the last increment.
  2. Under Post View, display only 2d_mesh(8) – 2d_mesh (12) plane stress elements of the strut.
  3. Use the Identify Results command and select all displayed elements using the Box(All) selection method.


  4. In the Identify dialog box, click Create Field to create a field from results with the following settings:
    • Name = FLT_STRUT_FACE_Manual
    • Independent Domain = Time, Axisymmetric Plane
    • Dependent Domain = Temperature
    • Duplicate Values = Average

Create field from results for HTC and fluid temperature for 1D elements

Export all of the results into one field to make the import and export of fields more manageable.

  1. Display the Total Absolute Fluid Temperature on Walls - Nodal of the last increment for only solver-created 1D elements.
    Whenever thermal boundary conditions are applied to the edges of 2D elements, the thermal solver automatically generates internal 1D elements for use in the solution and post-processing. Similarly, when thermal boundary conditions are applied to the faces of 3D elements, the solver internally generates corresponding 2D elements that are available for post-processing.
  2. Use the Identify Results command and select all displayed 1D elements using the Box(All) selection method.
  3. Click Create Field to create a field from results with the following settings:
    • Name = ALL_1D_FLT
    • Independent Domain = Time, Axisymmetric Plane
    • Dependent Domain = Temperature
    • Duplicate Values = Average
  4. Repeat the process for Convection Coefficient results.
  5. In the Simulation Navigator, under the Fields node, select all generated fields and export them as a .fld file.
    The next step is to move to the 3D model and map the extracted fields onto the corresponding surfaces of the 3D geometry.

Load the 3D model and inspect thermal boundary conditions

Open the 3D submodel and review existing convection boundary conditions.

  1. Open convective_results/3D/assyfem1_sim1.sim.
    Notice that the model uses an assembly FEM. This configuration duplicates the FEM at multiple angular positions, allowing you to verify that imported axisymmetric fields apply correctly across the cyclic geometry.
  2. Observe that the model already contains two convection boundary conditions.
    The component on which they are applied has two overlapping face convection boundary conditions, so you must handle the mapping from the 2D model differently in this region.

    Use Inner Shield_Convection to represent convection from the cold-side air. Keep its HTC consistent with the 2D model and assign the fluid temperature using the field extracted from the strut face in the 2D analysis.

    The CZ_Outer_Shield boundary condition matches the one applied in the 2D model, except that the area correction used in 2D is not required in the 3D model.

Import fields and modify convection definition

Import fields generated from the 2D model and assign mapped fluid temperature data to existing 3D convection boundary conditions.

  1. In the Simulation Navigator, right-click Fields and select Import navigate to the .fld file which you exported from the 2D analysis.
    Notice, there are 4 fields imported to your model.
  2. In the Simulation Navigator, right-click Inner Shield_Convection and select Edit.
  3. In the Temperature Value box, click and choose Select Existing Field and select the existing field you imported representing fluid temperature on the strut face.
  4. Right-click Inner Shield_Convection and select Plot Contours to verify applied temperature field.
  5. In the Selected Boundary Conditions group, in the Property column, right-click the Convective Coefficient and select Temperature Value.
  6. Set Time to 700s and click Plot .

    Use the Feature command in the Display tab to show only feature edges in the postview.



Create convection boundary condition on strut

Apply mapped convection boundary conditions to strut faces using imported HTC and fluid temperature fields.

  1. Choose Home > Loads and Conditions > Constraint Type > Convection to Environment
  2. Select strut faces using the Tangent Faces method as shown.


  3. In the Convection Coefficient and Temperature Value boxes, select the imported fields representing the strut for HTC and fluid temperature, respectively.
  4. Plot contours at 700[s] to verify axisymmetric field behavior.


    Convection Coefficient Temperature Value

Apply convection to surfaces corresponding to 1D elements

Apply convection boundary conditions on 3D surfaces corresponding to 1D edge locations from the 2D analysis.

  1. Create a new Convection to Environment constraint.
  2. Select the faces as shown below.


    24 faces are selected. These faces correspond to the locations of 1D elements in the 2D analysis. We can include all surfaces in one convection to environment constraint to save time.

  3. In the Convection Coefficient and Temperature Value boxes, select the imported fields corresponding to the 1D element results we extracted from 2D.
  4. Plot contours at 700[s] to confirm correct application.


    Convection Coefficient Temperature Value

Solve 3D model and compare with 2D results

Solve the 3D model and compare metal temperatures to validate the mapped convection results.

  1. Solve the 3D solution.
  2. Compare metal temperatures between 2D and 3D models.
  3. Verify consistency of mapped convective behavior.








Additional notes

  • Mapping HTC and fluid temperature allows asymmetric effects to be introduced in 3D submodels.
  • When applying known fluid temperatures and heat transfer coefficients, either a Thermal Convecting Zone or a Convection to Environment can be used. However, if total temperature effects must be considered, a Thermal Convecting Zone is required.
  • If only metal temperatures are required, use the separate Thermal Mapping workflow instead.