We demonstrate that in plane Couette turbulence a separation of the velocity field large and small scales according to streamwise Fourier decomposition allows us identify an active subspace comprising number gravest components flow can synchronize all remaining components. The critical wavelength, $\ell _{x c}$ , separates from synchronized passive is identified as wavelength at which perturbat...

Abstract With the mass application of drones in daily work, more attention has been paid to noise problem. The generation mechanism low Reynolds number propellers is studied this paper. It found that there are laminar separation bubbles on suction surface, causing an increase broadband noise. Leading edge boundary layer trips added remove bubbles. Finally, experimental measurements indicate iso...