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Basics of Modeling Turbulent Flow in COMSOL Multiphysics^®

With COMSOL Multiphysics^® and the add-on CFD Module, you can model turbulent flow using a wide range of turbulence models as well as large eddy simulation (LES) and detached eddy simulation (DES). In this article, we provide a comprehensive introduction to this process.

Note: If you are new to modeling fluid flow in the software, please start with our article on modeling laminar flow.

Discussion: Turbulent Flow Modeling

In this introductory video on single-phase, turbulent flow modeling, we begin by discussing the fundamentals of fluid flow modeling as well as turbulent flow modeling. Following this, we provide an overview of the turbulence models available in COMSOL Multiphysics^® and discuss their computational costs.

Here, you can find an outline of the video topics:

• Fundamentals of modeling turbulent flow
• Laminar, transitional, and turbulent flow
  • Turbulent viscosity term ()
  • Computational cost of turbulence models
  • Algebraic turbulence models
  • Two-equation transport equation turbulence models
  • One- and three-equation transport equation turbulence models
• Wall treatment
  • Resolution for low-Re wall treatment
• LES and DES

Demo: Turbulent Flow Modeling

In this video, we demonstrate how to set up turbulent flow models in the software. With this, you will see the model-building process from start to finish. After demonstrating the model setup, we highlight important settings and features that you should be aware of when modeling turbulent flow.

Here, you can find an outline of the video topics:

• Setting up, building, and computing a laminar flow model
  • Converting to a turbulent flow model
  • Refining the mesh
  • Adding a plot of recirculation zone
• Extending the model
  • Computational cost of different turbulence models
  • Overview of wall functions
  • Improving convergence
  • Generate New Turbulence Model Interface feature

Modeling Exercises

To gain hands-on experience with the topics discussed here, complete the following exercise with the Turbulent Flow over a Backward-Facing Step demo model:

1. Starting with a blank model, reproduce the 2D turbulent backstep model. (You can use these slides as a guide.)
   • Set up, build, and compute the model with an inlet velocity of 10 m/s
     • Geometry: turbulent_backstep_geom_sequence.mph
   • Add a plot of recirculation zone
2. Extend the turbulent backstep model to:
   • Use the k-ω turbulence model
   • Compare the number of iterations and the computation time between the k-ε and k-ω turbulence models

Note that the directions attached to this article are generalized so that you may also gain experience with self-guided problem solving. You can manually check your work with the solution model files provided here (the demo MPH files) or use the comparison tool to identify the differences.

Further Learning

To learn more, check out our blog post Which Turbulence Model Should I Choose for My CFD Application?.