Numerical investigation of turbulence in a skewed three dimensional channel flow
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- Institutt for marin teknikk 
The present doctoral thesis concerns fluid flow in three-dimensional turbulent boundary layers. In such flows, both the direction and the magnitude of the mean flow vary with wall distance. A statistically stationary turbulent shear layer was generated in a plane channel configuration where the mean three-dimensionality was achieved by means of a spanwise pressure gradient. Direct numerical simulations were performed to solve the incompressible Navier-Stokes equations. Reynolds-averaged statistics and details of the ensemble-averaged near-wall coherent vortices of the skewed flow field were presented. Results from a unidirectional reference flow were also presented. In particular, the impact of mean-flow three-dimensionality on coherent vortices with opposite sense of rotation was investigated. Asymmetries in the vortex pattern which are impossible in two-dimensional boundary layers were observed. A model has been proposed to interpret structure modifications in three-dimensional wall-flows.