PARTIALLY AVERAGED NAVIER-STOKES METHOD FOR TURBULENCE CLOSURES: CHARACTERIZATION OF FLUCTUATIONS AND EXTENSION TO WALL BOUNDED FLOWS

Partially Averaged Navier-Stokes Method for Turbulence Closures: Characterization of Fluctuations and Extension to Wall Bounded Flows. (May 2009) Sunil Lakshmipathy, B.E., Bangalore University; M.S., Texas A&M University Chair of Advisory Committee: Dr. Sharath S. Girimaji The work presented in this dissertation concerns continued development, validation and verification of the partially averaged Navier-Stokes (PANS) method – a variable resolution closure model for turbulence. Linear eddy viscosity models (LEVM), which are popular because of their simplicity and affordability in terms of computational cost have fundamental deficiencies and cannot be trusted to accurately represent turbulence in realistic complex flows. The more high fidelity approaches such as large eddy simulations (LES) and direct numerical simulations (DNS) are out of realm of engineering applicability because of their high requirements in computing power. PANS, a variable resolution approach considered in this study, lies between LEVM and LES in terms of computational cost and is designed to prudently utilize the available computing power to improve accuracy. This dissertation presents the various studies performed to characterize the PANS fluctuations and extend the model for use in various wall bounded flows. The road map towards our goal includes: (i) Comparing a-priori and a-posteriori eddy viscosity values to establish whether PANS is capable of producing the pre-specified level of reduction. (ii) Investigating the scaling of PANS fluctuations for different levels of prescribed resolution and establishing if the fluctuations abide by known turbulence scaling laws. (iii) Extending PANS to k-ω formulation which is better suited for wall-bounded shear