Ethan Rollier and Daniel Mutlyashki from Dassault Systèmes, along with collaborators from École Centrale de Lyon, present their work on the validation of simulations for stirred tank reactors at a NAFEMS seminar. The presentation covers the context and introduction to stirred tank reactors, commonly used in the medical, pharmaceutical, cosmetics, and food industries to create optimal fluid environments for biological and chemical processes. The focus is on two main goals: catalyzing bioprocesses (mixing, heating) and ensuring living conditions (oxygenation, substrate concentration, pH, temperature, low shear-stress). The talk then delves into the specifics of reactor design, including tank/vessel geometry, stirrer geometry, baffles, living conditions during the process, controlling and measurement of various types, and additional modelling considerations. Challenges in bioreactor design, such as maintaining optimal living conditions and process control, are also discussed. The validation section of the presentation covers simulations with a single and double Rushton turbine. For the single Rushton turbine, the study focuses on the Local Rotating Frame (LRF) size dependency, impeller velocity influence, and grid dependency. They discuss the simulation settings, including boundary conditions and mesh resolution, and present results on radial and axial velocity profiles and power number correlations. For the double Rushton turbine, the presentation highlights a lab-scale reactor setup and simulation results, including power number measurements, flow field observations, and particle tracking. Reference studies for both single and double turbines are cited to validate the simulation results. In conclusion, they discuss further work, including mesh resolution and LRF sizing studies, best practices for future studies, and extended validation for more complex reactors considering thermal effects, multiphase/mixing, particle tracking, reactions, and process monitoring. The presentation ends with a focus on workflow and process for bio-processes, chemical processes, phase change, and bubble formation and tracking.