ENGINEERING AND CFD

Many wall-bounded flows in nature and technology are affected by the surface roughness of the wall. In some cases, this has adverse effects, e.g. drag increase leading to higher fuel costs; in others, it is beneficial for mixing enhancement or transfer properties. Computationally, it is notoriously difficult to simulate these flows because of the vast separation of scales in highly turbulent flows and the challenges involved in handling complex geometries. The studies are carried out in two paradigmatic and complementary systems in turbulence research, Taylor-Couette and Rayleigh-Bénard flow.

Turbulent thermal convection plays an essential role in a wide range of natural and industrial settings, from astrophysical and geophysical flows to process engineering. While heat transfer in industrial applications takes place in confined systems, the aspect ratio in many natural instances of convection is huge. Interestingly, flow organization on enormous scales is observed in, for example, oceanic and atmospheric convection. However, our physical understanding of the formation of turbulent superstructures is limited. In this project, we analyze the flow organization within turbulent superstructures and show that their size increases when the thermal driving is increased.

Rayleigh-Benard flow (the flow in a box heated from below and cooled from above) and Taylor-Couette flow (the flow between two counter-rotating cylinders) are the two paradigmatic systems in the physics of fluids, and many new concepts have been tested with them. Researchers from the Physics of Fluids group at the University of Twente have been carrying out simulations of these systems on HLRS supercomputers to try and improve our understanding of turbulence.