The minimal flow unit in complex turbulent flows

Abstract

Direct numerical simulations of spanwise-rotating periodic turbulent channel flow were conducted for three rotation numbers: Rob = 0, 0.2, and 0.5 at a Reynolds number of 8000 based on laminar centerline mean velocity. An additional simulation was conducted at a Reynolds number of 27 000 and rotation number Rob = 0.2 to study higher-Reynolds number effects. In order to determine the proper computational box size for a minimal flow unit (MFU) at Rob = 0.5, spanwise arrays of Taylor–Gortler vortices in the highly turbulent pressure region were examined and complete realization of the vortices was demonstrated to be necessary for accurate MFU turbulence statistics requiring a minimum spanwise domain length Lz = π. An equivalent MFU model produced similar results for Rob = 0.2 but demonstrated decreased accuracy for the higher-Reynolds number simulation. Analysis of pressure statistics also showed that the MFU model could accurately approximate mean pressure but not fluctuating pressure distributions across t...