Global energy budgets in turbulent Couette and Poiseuille flows

Turbulent plane Poiseuille and Couette flows share the same geometry, but produce their flow rate owing to different external drivers, pressure gradient shear respectively. By looking at integral energy fluxes, we pose answer question of which performs better creating rate. We define a {\em efficiency}, that quantifies fraction power used instead being wasted as turbulent overhead; effectiveness}, instead, describes amount produced by given power. The work Gatti \emph{et al.} (\emph{J. Fluid Mech.} vol.857, 2018, pp. 345--373), where constant input (CPI) concept was developed compare with drag reduction, is here extended flows. decomposing mean velocity field into laminar contribution deviation, analytical expressions are derived energy-flux equivalents FIK identity. These concepts applied literature data supplemented new set direct numerical simulations, find less efficient more effective than ones. reason traced component flows, compensates for higher activity. It also observed that, when fluctuating fields two fed total fraction, dissipate smaller percentage it via dissipation. A decomposition large small scales explains this feature: develop stronger large-scale structures, alter while contributing significantly