Direct Numerical Simulation of turbulent wakes behind different plate configurations
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- Institutt for marin teknikk 
The physics of complex three-dimensional wake behind multiple flat plates is studied by means of direct numerical simulations (DNS). The interaction and interference effects between the wakes behind two configurations of flat plates, i.e. intersecting and parallel, inspired by various arrangements of cylindrical structures in the marine engineering field, were explored. First, the wake flow behind a cross formed by two intersecting perpendicular flat plates (cross-plate) placed normal to the inflow direction is considered. Results concerning the vortex dynamics, instability in the shear layer, mean flow structure i.e. formation of swirling vortices are presented and discussed. The wake behind T-shaped intersecting flat plates, in comparison with the cross configuration is investigated afterwards. In spite of some similarities, major features of the wake behind the T-plate turned out to be different from the wake behind a cross-plate configuration, in particular the formation of swirling vortices close to the internal corners. At the end, the wake behind two parallel plates in a side-by-side arrangement, placed normal to the inflow at different gap ratios is addressed. The wake interference effects, vortex dynamics, instability in the shear layer and three-dimensional instability modes are explored. The characteristic features of the flow are investigated by means of frequency analysis and flow visualization. Moreover, analogy between a plane mixing-layer and the separated shear-layer in the wide wake are examined.