Direct numerical simulations of Taylor-Couette turbulence: dynamics of the fully rough regime*

Due to its abundance in nature and industry, the study of turbulent flows over rough surfaces is of paramount importance. The key question is how any rough geometry maps to its fluid dynamic behavior. However, the study of open systems is hampered by accurate measurements of the skin-friction drag and the presence of very long spatial structures.  In this research, we employ Direct Numerical Simulations (DNSs) of a closed system, Taylor-Couette flow. Whereas before we have focused on transitionally rough surfaces, here we focus on the local and global fluid flow response over fully rough surfaces. In particular we study the azimuthal (streamwise) velocity and angular velocity profiles for varying friction Reynolds number and constant viscous roughness heights.