Waves of spanwise velocity imposed at the walls of a plane turbulent channel flow are studied by Direct Numerical Simulations. We consider sinusoidal waves of spanwise velocity which vary in time and are modulated in space along the streamwise direction. The phase speed may be null, positive or negative, so that the waves may be either stationary or traveling forward or backward in the directio...

Measurements of the streamwise and spanwise fluctuating velocity components are obtained in a high Reynolds number turbulent boundary layer using custom made sub-miniature hot wires. These measurements are made over a range of Reynolds numbers from Reτ ≈ 3,000 to Reτ ≈ 10,500, but at fixed unit Reynolds number U∞/ν (Reτ = δUτ/ν; where ν is the kinematic viscosity, Uτ is the friction velocity an...

A spanwise array of 10 surface mounted hot-film shear-stress sensors coupled with a traversing hot-wire probe are used to identify the conditional structure associated with a large-scale skin-friction event in a high Reynolds number turbulent boundary layer (Reτ 14000). Instantaneous shear-stress data indicate the presence of large-scale structures at the wall that are comparable in scale and a...

CD = dimensionless mean drag coefficient, 2F D= fU meanD F D = drag force per unit spanwise length on the cylinder and plate, Nm 1 D = diameter of the cylinder, m E = dimensionless Young’s modulus, E = fU mean f = dimensionless oscillation frequency of the plate, f D=Umean Re = Reynolds number, fUmeanD= Umean = mean velocity at the left boundary of the channel, ms 1 V = dimensionless dilatation...

Cf = skin-friction coefficient f = frequency fs = frequency of shock motion J = Jacobian matrix of the grid transformation Lsep = separation length M = freestream Mach number p = pressure Re = Reynolds number based on Re = Reynolds number based on Re = Reynolds number based on Sij = rate-of-strain tensor SL = dimensionless frequency of shock motion based on Lsep and U1 T = temperature u = veloc...

A direct numerical simulation of incompressible channel flow at Reτ = 5186 has been performed, and the flow exhibits a number of the characteristics of high Reynolds number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant κ = 0.384 ± 0.004. There is also a logarithmic dependence of the variance of the s...