Advanced OpenFOAM CFD: Dynamic Meshes And Motion

In this module, we move beyond rotating walls and introduce Multiple Reference Frame (MRF) simulations, a powerful technique used to model rotating machinery within a stationary mesh.

MRF allows you to define rotating regions inside the computational domain while keeping the simulation steady-state, making it significantly more efficient than time-accurate sliding or dynamic mesh approaches.

MRF is widely used for simulating fans, pumps, compressors, turbo-machinery, and propellers when transient effects are not required.

In this module, you will learn:

• The physical concept behind Multiple Reference Frames

• How MRF differs from rotating walls and sliding mesh approaches

• How to define rotating zones, axes, and angular velocities

• How to correctly set up MRF in OpenFOAM

• Common setup errors and how to debug them

• How to interpret results from MRF simulations

By the end of this module, you will be able to confidently build stable, efficient MRF simulations and understand when MRF is the correct modeling choice versus more advanced transient methods covered later in the course.

In this module, we take the next major step in motion modeling by introducing sliding mesh simulations in OpenFOAM.

Unlike rotating walls and MRF, sliding meshes explicitly rotate the mesh itself and exchange information across moving interfaces, allowing you to capture true transient effects such as blade-passing interactions and unsteady flow phenomena.

Sliding mesh simulations are commonly used for rotors, turbines, compressors, gear systems, and rotating machinery where time-accurate physics are required.

In this module, you will learn:

• When sliding meshes are required instead of MRF

• The physical and numerical principles behind sliding interfaces

• How to define rotating and stationary mesh regions

• How to set up sliding interfaces correctly in OpenFOAM

• Time-step selection and stability considerations

• Common errors and how to fix them

By the end of this module, you will be able to build robust, time-accurate sliding mesh simulations and understand the trade-offs between accuracy and computational cost compared to MRF.

In this module, we introduce dynamic mesh simulations, where the computational mesh moves and deforms in time to follow prescribed motion.

Dynamic meshes allow you to model cases where objects translate, rotate, oscillate, or deform while maintaining a single, connected mesh. This approach is commonly used for valves, pistons, flapping surfaces, moving boundaries, and mechanisms with complex motion.

In this module, you will learn:

• The difference between sliding meshes and dynamic meshes

• How dynamic mesh motion is defined and controlled in OpenFOAM

• Prescribing linear, rotational, and oscillatory motion

• Mesh deformation techniques and quality control

• How to prevent mesh distortion

• Time-step and stability considerations for dynamic motion

By the end of this module, you will be able to confidently set up robust dynamic mesh simulations and understand when dynamic meshes are the correct choice compared to sliding or overset mesh approaches.

In this module, we introduce overset mesh simulations, one of the most flexible approaches for modeling complex relative motion in OpenFOAM.

Overset meshes allow multiple, independent meshes to overlap and move freely relative to one another, removing many of the mesh quality limitations found in sliding or deforming mesh approaches.

This technique is especially powerful for simulations involving multiple moving bodies, large relative motion, or complex geometries, such as vehicles with rotating wheels, store separation, moving machinery, and aerospace applications.

In this module, you will learn:

• The fundamental concept behind overset (chimera) meshes

• How overset meshes differ from dynamic and sliding meshes

• Defining background and overset regions correctly

• Overset interpolation

• Common overset mesh stability issues and how to fix them

• Performance and accuracy considerations

By the end of this module, you will be able to build robust overset mesh simulations and confidently decide when overset meshes are the best choice for your motion problem.

In this module, we focus on reducing computational cost while maintaining accuracy — a critical skill for running advanced motion simulations efficiently.

Complex simulations involving MRF, sliding meshes, dynamic meshes, and overset meshes can quickly become computationally expensive if not configured correctly. In this module, you will learn how to identify performance bottlenecks and apply targeted optimizations.

You will learn:

• How mesh resolution and refinement impact runtime

• Choosing appropriate time steps and Courant limits

• Parallelization strategies and efficient domain decomposition

By the end of this module, you will be able to run advanced OpenFOAM simulations faster, more reliably, and with greater confidence, saving hours—or even days—of computational time.