The spatial signatures of retrograde spanwise vortices in wall turbulence are assessed from particle-image velocimetry measurements in the streamwise–wall-normal plane of a zero-pressure-gradient turbulent boundary layer at Reτ ≡ u∗δ/ν=2350. The present results suggest that a proportion of retrograde spanwise vortices have a welldefined spatial relationship with neighbouring prograde vortices. ...

We investigate the onset of temporal dynamics a fluidic oscillator (FO) in laminar regime at very low Reynolds number (Re=Uhi/ν, where U and hi are velocity channel height inlet, ν is kinematic viscosity fluid). Both two- spanwise-periodic-three-dimensional simulations performed using high-order spectral element methods to characterise flow inside FO cavity outcoming jet. While remains steady s...

A new adaptive controller based on a neural network was constructed and applied to turbulent channel flow for drag reduction. A simple control network, which employs blowing and suction at the wall based only on the wall-shear stresses in the spanwise direction, was shown to reduce the skin friction by as much as 20% in direct numerical simulations of a low-Reynolds number turbulent channel flo...

Turbulent drag reduction (DR) through streamwise travelling waves of the spanwise wall oscillation is investigated over a wide range Reynolds numbers. Here, in Part 1, wall-resolved large-eddy simulations channel flow are conducted to examine how frequency and wavenumber wave influence DR at friction numbers $Re_\tau = 951$ $4000$ . The actuation parameter space restricted inner-scaled (ISA) pa...

Direct numerical simulations are performed to investigate the three-dimensional stability of compressible flow over open cavities. A linear stability analysis is conducted to search for three-dimensional global instabilities of the two-dimensional mean flow for cavities that are homogeneous in the spanwise direction. The presence of such instabilities is reported for a range of flow conditions ...