Numeriska simuleringar av turbulent strömning i roterande system

Different aspects of numerical simulations of turbulent flows are assessed by consideringa fully-developed turbulent channel flow that is rotating in the spanwise direction.Differences between differential and explicit algebraic Reynolds-stress models(RSMs) are investigated theoretically and numerically. Simulation results are comparedwith existing DNS-data. Both families of RSMs are demonstrated to achievegood qualitative agreement with the DNS. The results constitutes a demonstration ofthe validity of the so called extended weak-equilibrium assumption for systems witha superimposed solid body rotation. An original derivation, based on sound physicalgrounds, of the extended weak-equilibrium assumption is presented.It is further examined if the roll-cell vortex pattern, that constitutes a secondaryflow field, has an influence on the averaged solutions obtained by application of theReynolds-Averaged Navier-Stokes equations. This is assessed by comparison of resultsobtained by either considering the secondary plane as homogeneous in the spanwisedirection or by accounting for a fully three-dimensional flow field. Simulationsdemonstrate that existence of roll-cells in the latter case yields results that are in closeragreement with DNS-data compared with if they are suppressed as for the former case.Aspects of numerical treatment of explicit source terms are also assessed in theframework of finite volume methods for collocated grids