Mixing Tank

MRF Method, Mixing Tank — ANSYS Fluent CFD Simulation

Description

This project is a comprehensive guide to applying the Multiple Reference Frame (MRF) method to a mixing tank in ANSYS Fluent. A mixing tank uses a rotating impeller to stir and blend fluid, and simulating it means capturing the interaction between the spinning impeller and the stationary tank around it. The MRF method handles this by dividing the domain into a rotating zone around the impeller and a stationary zone for the tank, solving each in its own reference frame — a steady, cost-efficient approach to rotating machinery. As the opening project of the MRF: Beginner CFD Training Package, it most directly teaches the MRF method itself — the multi-zone rotating/stationary setup that underpins every case that follows.

Methodology

The detailed 3D model is created in ANSYS Design Modeler and meshed in ANSYS Meshing with 229,177 unstructured elements, optimized for high-fidelity results. The setup configures the multiple zones required for the MRF method — a rotating zone around the impeller and a stationary zone for the tank — with a steady-state analysis and the k-ε turbulence model. The boundary conditions define a 500 rpm impeller rotation within the stationary tank, so the rotation is captured through the reference frame rather than by physically moving the mesh.

Analysis

Post-processing extracts pressure, velocity, and turbulent-intensity contours along with flow vectors. The pressure distribution reveals the variations around the impeller and their effect on mixing efficiency across the zones; the velocity profiles show the flow-speed patterns, particularly behind the impeller, and correlate them with mixing effectiveness in the rotating and stationary regions; the turbulence-intensity fields show where mixing is most vigorous, especially near the impeller; and the flow vectors reveal the vortex formation around the impeller and its impact on mixing. This kind of analysis is central to chemical and process engineering, pharmaceutical mixing, the food and beverage industry, and wastewater treatment. By the end of this project, you'll be able to set up a multi-zone MRF simulation with rotating and stationary zones, define an impeller rotation in a steady-state framework, and interpret the pressure, velocity, turbulence, and vector fields that characterize mixing performance in a stirred tank.