Centrifuge CFD Simulation, Two-Phase Flow (MIXTURE), ANSYS Fluent

Description

Centrifuge Problem description

In this project, the effect of steady rotation of a centrifugal turbine on a water and air two-phase mixture is investigated by ANSYS Fluent software. Multi-phase MIXTURE model is used to solve water and air phase interactions. The secondary phase (air) volume fraction has very low values in the 0.0001 order, which proves the validity of the mixture multi-phase model in this project, since for applying the Mixture Multi-Phase model, the secondary phase volume fraction should be less than 15%. Slip velocity has been taken into account at the water and air contact interface. The diameter of air bubbles is considered equal to 1 µm. The rotating region of the turbine is considered a separate body that rotates with a rotational speed equal to 500 rpm, which simulates the rotation of the centrifugal turbine at the same rate. Frame Motion (MRF) model has been applied for the rotation simulation.

Centrifuge Geometry and mesh

The geometry of the fluid domain is designed in the Design modeler and the computational grid is generated using Ansys meshing. The mesh type is unstructured, and the element number is 126000.

Solver Configuration for Centrifuge CFD Simulation

Critical assumptions:

• Solver type is assumed Pressure Based.
• Time formulation is assumed to be Steady.
• Gravity effects are considered in a positive Z direction equal to 9.84 m/s2.

The following table a summary of the defining steps of the problem and its solution.

Results and discussion

Rotation of the centrifugal turbine with the rotational speed of 500 rpm results in fluid movement with a velocity equal to 0.62 m/s at close ranges of the turbine. Water bubbles are captured under the turbine which increases the secondary phase (air) volume fraction in these regions.