Convective boundary condition configuration

Convective Boundary Condition Configuration in Twin Fabrica

In Twin Fabrica, a convective boundary condition models heat exchange between a solid body and its surrounding environment. This condition applies to the external surfaces of a geometry and follows the physical relation:

q = h · (T_surface - T_ext)

Where:

q is the heat flux,
h is the convective heat transfer coefficient
T_surface is the surface temperature,
T_ext is the external (ambient) temperature.

This section explains how to configure this boundary condition, assuming the boundary condition component has already been created. If not, please refer to the corresponding tutorial on component creation.

1. Select the Convective Type

Open the boundary condition configuration panel and select Convective from the drop-down menu.

This setting enables heat exchange between the selected geometrical surfaces and the external environment using the convection model.

2. External Temperature Setup

By default, Twin Fabrica uses a uniform external temperature across all affected surfaces.

For advanced cases with non-uniform temperature distributions, you can define a space function.
You can also set the temperature as a parametric function to model time- or input-dependent behavior.

These advanced features are covered in separate tutorials.

3. Define External Temperature (Constant Value)

In this guide, we use a constant temperature for simplicity:

Give the temperature parameter a descriptive name (e.g., Text_2) for easier tracking.
Set a default value (e.g., 20°C) for simulation use unless overridden by another setup.

4. Configure the Convective Coefficient

The convective heat transfer coefficient determines how efficiently heat transfers between the surface and environment.

Like temperature, this parameter can be space-dependent or parametric, but we'll use a constant value for simplicity.
Give the coefficient a clear label (e.g., h_2) to identify it in the parameter list.

5. Assign the Nominal Value

Enter the nominal value for the convective coefficient.

This value applies during Full Order Model simulations unless adjusted through parametric or calibration processes.

6. Apply to Geometrical Entities

Assign the boundary condition to specific surfaces in the model:

The configuration panel shows both 2D and 3D entities.
When you apply the condition to a 3D entity, Twin Fabrica automatically selects its external surfaces.

Choose the appropriate entities using the checkboxes.

7. Save the Configuration

Click SAVE to complete the convective boundary condition setup.

This action stores the configuration and connects it to the selected geometrical areas.

8. Verify Assignment

To confirm the boundary condition is properly configured:

Expand the Boundary Conditions node in the navigation tree.
Check that the small dot next to the boundary component name (e.g., boundary_2) disappears, indicating it's fully defined.
Select it to see the associated geometrical entities highlighted in the 3D viewer, confirming the application areas.