Twin forces: similarity between rotation and stratification effects on wall turbulence.

Can the similarity between rotation and stratification provide quantitative predictions for complex turbulence? In this work, we focus on plane Couette turbulence as the background flow, which allows us to eliminate the key differences between Rayleigh–Bénard and Taylor–Couette turbulence, and facilitates a quantitative mapping across many complex turbulent systems involving rotation, stratification and curvature effects. To characterize the separated or coupled effects of rotation and stratification, we introduce an overall Richardson number Ri_χ which is the sum of the Coriolis Richardson number Ri_θ and the buoyancy Richardson number Ri_T. When the Prandtl number Pr = 1, the heat and inertial-frame momentum transport almost coincide and mainly depend on Ri_χ and the Reynolds number, regardless of the specific ratio between Ri_θ and Ri_T. When Pr varies, the weighted average Nu_χ of the transport coefficients can still remain approximately invariant in most cases. Furthermore, the large-scale structures in purely rotating and purely stratified cases exhibit strikingly similar features. These findings not only indicate a more reasonable analogy for the ultimate Taylor–Couette turbulence but also pave the way for developing new predictive models for natural and industrial processes. [ABSTRACT FROM AUTHOR]