Numerical simulation of plane Couette flow subject to spanwise system rotation

Sammanfattning

This thesis investigates plane Couette flow subject to spanwise system rotation usingdirect numerical simulation (DNS). The objective is to recreate and compare with the re-sults from an experimental study, and to then extend the parameter space with Reynoldsnumbers Re ∈ [100, 2000] and rotation numbers Ro ∈ [0.0, 0.95]. This results in a flowregime map with the different flow states mapped out over the parameter space. Theparametric study is done with Reynolds number, Re, and a rotation number, Ro. Everysimulation is visualized with iso–surfaces of the Q–criterion, after which they are cate-gorized into different flow types depending on what characteristics they display. Someof these flow types have been identified in previous studies while others are introducedin this present study. Furthermore, direct and derived statistic quantities, such as theturbulent kinetic energy are measured and plotted. These include the mean streamwisevelocity gradient at the walls and the mean velocity profile. The results show that thesimulation can recreate the experimental results. They further demonstrate the effectof system rotation on flow stability and formation of roll cells, which varies from de-structive (anti–cyclonic) to constructive (cyclonic) for different levels of rotation. LowerRo-numbers are found to destabilize the flow while higher values stabilize it. This be-havior is consistent with the predictions of linear stability theory, which is further seenin the mean streamwise velocity gradient and the turbulent kinetic energy, which bothpeak at lower values of Ro, while decreasing as Ro → 1.