POD study on the mechanism of turbulent drag reduction and heat transfer reduction based on direct numerical simulation

Direct Numerical Simulations (DNSs) have been performed for turbulent channel flows of Newtonian fluid and drag-reducing fluid with heat transfer. Main coherent structures in the drag-reducing flow and heat transfer were extracted from the DNS database by Proper Orthogonal Decomposition (POD) method. The mechanisms of turbulent drag reduction and heat transfer reduction were studied through the analyses of the coherent structures and energy distribution reflected by different POD eigenmodes.