Turbulent shear flows subject to system rotation

Abstract

Turbulent flows in rotating frame-of-reference are of considerable interest in a variety of industrial, geophysical and astrophysical applications. In these flows, the system rotation induces additional body forces, i.e. centrifugal and Coriolis forces, acting on the turbulent flow, so that the momentum mechanism becomes more complicated. The present doctoral thesis concerns the system rotation influence on turbulent shear flows. To this end, direct numerical simulations (DNSs) have been performed in order to investigate the effect of system rotation on different turbulent flow configurations including plane Couette flow, sudden expansion flow and wake behind a flat plate. In addition, the PIV measurements for rotating plane channel and sudden expansion flows have been carried out in order to support the numerical simulations results.

A realistic turbulent inflow boundary condition is needed in order to perform direct numerical simulations for spatially developing flows subjected to system rotation such as rotating sudden expansion flows. The cost effective method is introduced based on a separate (precursor) simulation in order to establish fully turbulent inflow including wide ranges of length and time scales needed in the direct numerical simulations. On the other hand, the characteristic features of the rotating turbulent flows were investigated by means of three-dimensional flow visualization, two-point correlations and transport for the individual second-moments of the velocity and vorticity fluctuations.