Mixing of Fluid inside a Bioreactor


Bioreactors are cylindrical vessels that are used to carry out biochemical processes involving organisms. These vessels are filled with a liquid medium containing microorganisms or another bio matter. The chemical processes are usually aerobic and oxygen is the limiting nutrient because of its low solubility. These reactors, therefore, have a rotating impeller for enhanced mixing and uniform distribution of oxygen in the reactor. Shear rate, turbulence, and buoyancy are key parameters that influence mixing in such reactors and are critical to understanding the flow behavior. Bubble size distribution is a key parameter of interest in such simulations, which is usually obtained by running multiphase simulations involving the mixing liquid and air. In this simulation example, our focus will be to model the fluid mixing inside a bioreactor. As a first step in modeling complex physics of mixing in a bioreactor, we will not include multiphase aspects and use water (single-phase) as our mixing fluid in this simulation. The rotation of the impeller is modeling using the Moving Reference Frame approach (MRF) in Ansys Fluent.



This example simulates the mixing inside a cylindrical bioreactor. The tank contains an impeller and 4 baffle walls. The impeller is rotating at 250 rpm. The primary objective of this simulation is to understand the fluid flow inside this reactor. We will learn to set-up this problem in Ansys Fluent using the Moving Reference Frame (MRF) approach. We will also employ the Discrete Phase Modeling (DPM) in Ansys Fluent to inject and track inert particles for flow visualization.


Download the Mesh file needed for setting up the simulation and the associated Case & Data files here. Follow the instructions below to set up this simulation in Ansys Fluent starting with the Mesh file. In case you face any issues setting up or running the simulation, refer to the corresponding initial and final Case and Data files.

Results and Discussion

Let's take a look at the results from this simulation and understand the flow behavior inside the bioreactor.