Objective:

Learn how to run a nonlinear thermal analysis.

Applies to:

• Thermal Analysis

Procedure:

Note: This workflow uses Beta blocks. Learn how to turn on Beta blocks by reading: What are beta blocks?

Nonlinear vs. Linear Thermal Analysis

Nonlinear thermal analysis has the same setup as linear thermal analysis, except for the material properties and final analysis block. To run a nonlinear thermal analysis, we need nonlinear material properties.

Before starting, ensure you understand how to set up an analysis in nTop. Refer to this article for more information: How can I set up a simulation?

1. Define nonlinear thermal properties.

• Use the Isotropic Thermal Property block (or the Orthotropic Thermal Property block) to define nonlinear thermal properties. In this example, we use the Isotropic Thermal Property block with its nonlinear overload (Dictionary, Dictionary).
• Since we need several values to create a nonlinear thermal property, we use an overload with Dictionary input types. A Dictionary is a mapping block where you can form a set of keys and correspond them to key values. This is what we use to create the nonlinear values.
•  Use the nonlinear overload by using the down chevron and choosing (Dictionary, Dictionary).

• Double-click in the Conductivity input and select 'Dictionary'
• Double-click in the Keys input and select 'Temperature List'
• Double-click in the Keys input and select 'Scalar Field List'
• Select the icon chevron after and change the input to 'Scalar List' (since we don't need a Scalar Field List).

2. Complete the FE Model and choose your Boundary Conditions.

• In this example, we use two Temperature Restraint blocks and a Surface Heat Flux block for our Boundary Conditions.

3. Run the analysis.

• Add a Nonlinear Thermal Analysis block.
• This block performs a nonlinear steady-state heat conduction analysis on an FE Model subject to prescribed temperature and heat flux boundary conditions. All transient effects of heat transfer are neglected, and the temperatures are reported assuming that the system has reached equilibrium.
• Set the Maximum iterations. This is the maximum number of times the analysis will run.
• The values for Solution convergence and Reaction convergence are auto-populated.
• Optional: Add a value for the Output step. This outputs the results at every Nth time iteration.

In this example, our Nonlinear Thermal Analysis block has the following inputs:

Our results are shown in a Heads-Up-Display (HUD). You can visualize the Temperature, Heat Flux, and Thermal Reaction Flux in the HUD. You can access these properties by opening the Info panel and going to the Properties tab in the Nonlinear Thermal Analysis block.

And that’s it! You’ve successfully run a nonlinear thermal analysis

Are you still having issues? Contact the support team, and we’ll be happy to help!