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Basics of Modeling Laminar Flow in COMSOL Multiphysics^®

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With the COMSOL Multiphysics^®software, you can model laminar flow, and you can extend the modeling features and capabilities for modeling turbulent and multiphase flows by using the add-on CFD Module. Here, we provide a comprehensive overview of the basics of modeling laminar flow in the software. This article serves as a starting point if you are new to modeling any type of flow in COMSOL Multiphysics^®.

Discussion & Demo: Laminar Flow Modeling

In this introductory video on single-phase, laminar flow modeling in the software, we start off by discussing some fundamentals of fluid flow modeling. We then demonstrate using COMSOL Multiphysics^®for modeling laminar flow and walk through the model-building process from start to finish. Following this, we highlight various settings, features, and boundary conditions of theLaminar Flowinterface.

The following topics are covered in the video:

• Fundamentals of fluid flow modeling
• Single-Phase Flowinterfaces
  • Laminar Flowinterface
• Demo: setting up, building, and computing a laminar flow model
  • Backstep tutorial model
• Demo: extending the model
  • How is the recirculation zone affected by the inlet velocity?
  • When do we need to elongate the outlet section?
  • Extending the model with a parameter sweep
  • Plotting recirculation zone as a function of inlet velocity
• Laminar Flowinterface
  • Settings
  • Features
  • Boundary conditions

Modeling Exercises

Demonstrate the knowledge you have gained from this article by putting it into practice with theStationary Incompressible Flow over a Backsteptutorial model:

1. Starting with a blank model, reproduce the backstep model. (You can usethese slidesas a guide.)
   • Parameters:backstep_parameters.txt
   • Geometry:backstep_geom_sequence.mph
2. Extend the model to include:
   • Varying inlet velocity (specify a range from 0.0025 m/s to 0.015 m/s, with a step size of 0.0025 m/s)
   • Plot of recirculation zone as a function of inlet velocity

The directions (attached to this article) are intentionally generalized to encourage self-guided problem solving. You can manually check your implementation with the solution model files forreproducing the modelandextending the modelprovided here or you can use thecomparison toolto identify the differences.

Further Learning

• Multiphysics Cyclopedia:
  • Fluid Flow: Conservation of Momentum, Mass, and Energy
  • Navier–Stokes Equations
• Blog posts:
  • Characterizing the Flow and Choosing the Right Interface
  • How to Place Inlet and Outlet Boundary Conditions in CFD Simulations