The objective of this paper is to examine the effectiveness of wall oscillation as a control scheme of drag reduction. Two flow configurations are considered: constant flow rate and constant mean pressure gradient. The Navier-Stokes equations are solved using Fourier-Chebyshev spectral methods and the oscillation in sinusoidal form is enforced on the walls through boundary conditions for the sp...

This paper reviews turbulent boundary-layer control strategies for skin-friction reduction of aerodynamic bodies. The focus is placed on the drag-reduction mechanisms by two flow control techniques-spanwise oscillation and spanwise travelling wave, which were demonstrated to give up to 45 per cent skin-friction reductions. We show that these techniques can be implemented by dielectric-barrier d...

The objective of this paper is to examine the effectiveness of wall oscillation as a control scheme of drag reduction. Two flow configurations are considered: constant flow rate and constant mean pressure gradient. The Navier-Stokes equations are solved using Fourier-Chebyshev spectral methods and the oscillation in sinusoidal form is enforced on the walls through boundary conditions for the sp...

Turbulence control in the form of transverse wall motion is employed numerically (direct numerical simulation). Results from a turbulent boundary layer subjected to spanwise wall forcing in the form of a streamwise travelling wave are presented for the first time. Both total and phase averaging have been utilized to examine the statistical behaviour of the turbulence affected by the wall forcin...

Spanwise wall oscillations alter the organization of low-speed streaks and ejections in turbulent boundary layers, eventually leading to skin friction drag reduction. Such flow regimes are represented by pointwise statistics or spatial correlation. This work attempts quantify systematic distortions dominant structures feature-analysis, intended overcome dispersion observed correlation functions...

Drag-reduction techniques capable of reducing the level of turbulent friction through wall-parallel movement of the wall are described, with special emphasis placed on spanwise movement. The discussion is confined to active open-loop control strategies, although feedback control is briefly mentioned with regard to peculiarities of spanwise sensing and/or actuation. Theoretical considerations ar...

Drag-reduction techniques capable of reducing the level of turbulent friction through wall-parallel movement of the wall are described, with special emphasis placed on spanwise movement. The discussion is confined to active open-loop control strategies, although feedback control is briefly mentioned with regard to peculiarities of spanwise sensing and/or actuation. Theoretical considerations ar...

Spanwise wall oscillation is an easily implemented active control scheme. It can delay the transition to turbulent flows in incompressible boundary layers under appropriate parameters. However, this delayed compressible has not yet been confirmed numerically. In paper, we perform a series of direct numerical simulations spatially developing subsonic layer with different spanwise periods and amp...

A = hole surface Ma = Mach number Re = Reynolds number reff = effective hole radius rmod = modified hole radius q = heat flux at the wall T = temperature T = spanwise mean temperature u, v, w = velocity in x, y and z direction x = downstream coordinate y = wall-normal coordinate z = spanwise coordinate = boundary-layer thickness = emission coefficient = cooling effectiveness = spanwise mean coo...