Bioreactor Agitated by Rushton Turbine CFD Simulation, ANSYS Fluent Tutorial

The problem simulates fluid mixing in a Bioreactor with a Rushton Turbine using ANSYS fluent software. We perform this CFD project and investigate it by CFD analysis.

Bioreactors are equipment and systems in which biochemical reactions occur and are used in various industries, including pharmaceutical, food, biochemical, perfumery, etc. The bioreactor modeled in this simulation has a cylindrical structure.

A stirrer is placed vertically inside it to rotate the fluid flow inside this model to help the fluid mix and thus the desired chemical process. The stirrer used inside this reactor is a Rushton-type turbine.

Rushton turbines are in the form of radial flow type impellers widely used in mixing applications in engineering processes.

The present model is designed in three dimensions using Design Modeler software. The model includes a bioreactor with a cylindrical structure of 0.8 m high and 0.4 m in diameter with a vertical stirrer. The vertical stirrer of this model has two rows of flat discs with six blades mounted on it.

The meshing of the model has been done using ANSYS Meshing software. The element number is 3558726. Also, the transient solver is enabled due to the nature of the problem, which is time-advancing.

Rushton Methodology

These stirrers’ structure consists of flat discs connected to a vertical rotating axis on which the flat blades are mounted vertically. The Rushton turbine in this modeling consists of two rows of wide discs with blades.

A cylindrical inner region is distinguished within the model to define the fluid’s rotational flow around this Rushton turbine stirrer, which can be applied using the Mesh Motion technique.

The rotational velocity value in this region is equal to 143 rpm and is defined around the model’s vertical central axis (Y-axis). Also, three rows of baffles are designed on the bioreactor cylindrical body’s inner surface, which is used to break the vortices inside the device.

Furthermore, the RNG k-epsilon model is used to solve turbulent fluid equations.

Rushton Conclusion

At the end of the solution process, three-dimensional contours related to the pressure gradient, velocity, and turbulent kinetic energy of the device’s water flow are obtained.

Two-dimensional contours of pressure, velocity, and turbulent kinetic energy of water flow in two two-dimensional sections perpendicular to the stirrer’s axis and passing through two stirrer disks are obtained.

The contours show the increase in velocity and rotation of the flow around the impeller turbine impellers. Also, water velocity vectors around the stirrer axis are obtained in two and three dimensions.

Examining these velocity vectors’ trajectories makes it clear that the fluid flow rotates entirely around the stirrer’s axis of rotation.