The MRF method stands for multiple reference frame, which is a way of modeling a rotating fan or any other moving part in a fluid flow simulation. The MRF method allows you to divide your domain into different zones, each of which can have a different rotational or translational speed. For example, you can create a zone for the fan region that is rotating at a certain angular velocity, and another zone for the rest of the domain that is stationary.
The MRF method solves the flow equations in each zone using the moving reference frame equations, which account for the relative motion between the zones. The moving reference frame equations are derived from the Navier-Stokes equations by applying a coordinate transformation that accounts for the rotation and/or translation of the reference frame. You can find more details about the derivation and formulation of the moving reference frame equations in this section⁶ of the Ansys Fluent Theory Guide.
At the interfaces between zones, a local reference frame transformation is performed to enable flow variables in one zone to be used to calculate fluxes at the boundary of the adjacent zone. This ensures that the flow is continuous and conservative across the interfaces. For more information about the MRF interface formulation, see this section⁵ of the Ansys Fluent User's Guide.
The MRF method is a steady-state approximation, which means that it assumes that the flow does not change over time. This makes it simpler and faster to solve than other methods that capture transient effects or interactions between the fan and the fluid. However, the MRF method also has some limitations, such as not being able to model unsteady phenomena like blade flutter or stall, or not being able to handle complex geometries or mesh motions.
To use the MRF method in Ansys Fluent, you need to follow some general steps:
- Create or import a geometry of the fan and the fluid domain in Ansys DesignModeler or any other CAD software.
- Mesh the geometry using Ansys Meshing or any other meshing software. Make sure to create a separate zone for the fan region and apply appropriate boundary layer and inflation settings.
- Import the mesh into Ansys Fluent and set up the solver settings, such as the turbulence model, the operating pressure, and the solution methods.
- Define the boundary conditions for the inlet, outlet, walls, and fan regions. For
the fan region, you need to specify a rotating wall boundary condition with a constant angular velocity. You also need to enable the MRF option for the fan zone and define its axis of rotation.
- Initialize and run the simulation until convergence. You can monitor the residuals, forces, moments, and other quantities of interest during the solution process.
- Post-process and visualize the results using Ansys Fluent or any other post-processing software. You can plot contours, vectors, streamlines, iso-surfaces, and other graphical features to analyze the flow field and heat transfer around the fan.
If you want to learn more about how to uset he MRF method in Ansys Fluent,you can watch some video tutorials on YouTube that demonstrate this process step by step. For example,you can watch this video¹ by Alpha Omega Product Development Systems,which shows how to model an axial fan in Ansys Fluent using the MRF method. You can also watch this video² by CFD NINJA, which shows how to model an axial fan in Ansys Fluent using both the MRF and sliding mesh methods.
I hope this answer helps you understand more about the MRF method in Ansys Fluent. If you have any other questions, feel free to ask me. 😊
Source:
(1) ANSYS FLUENT 12.0 Theory Guide - 2.3.1 The Multiple Reference ... - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/th/node33.htm.
(2) ANSYS FLUENT 12.0 User's Guide - 10.3.1 The Multiple Reference ... - ENEA. https://www.afs.enea.it/project/neptunius/docs/fluent/html/ug/node370.htm.
(3) Ansys Fluent Tutorial for beginners | Multiphase Flow | Three Phases | Ansys Workbench. https://www.youtube.com/watch?v=QgQTaXuPmbI.
(4) Ansys Fluent tutorial for beginners. https://www.youtube.com/watch?v=Xq0WsxL0hZQ.
(5) Performing Parametric Analyses Using Ansys Fluent. https://www.youtube.com/watch?v=4bZqL9ZNJwA.
(6) ANSYS Fluent Tutorial | Multiple Reference Frame (MRF) | ANSYS .... https://www.youtube.com/watch?v=A3bnO5r2SWQ.
(7) undefined. https://files.mecht.in.
(8) undefined. https://www.instagram.com/mech_tech.90/.
(9) https://www.facebook.com/mechtechpage/.
(10) http://www.ansys-tutor.blogspot.com.
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