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...

A known difficulty with using the Clauser chart method to determine the friction velocity in wall bounded flows is that it assumes, a priori, a logarithmic law for the mean velocity profile. Using both experimental and DNS data in the literature, this note explicitly shows how friction velocities obtained using the Clauser chart method can potentially mask subtle Reynolds-number-dependent behav...

Amagnetohydrodynamic flow of a viscous, incompressible and slightly conducting fluid is developed between a parallel flat wall and a wavy wall whereas at the same time fluid is continuously sucked through the flat wall with a constant suction velocity. The velocity and temperature distribution are determined alongwith the pressure gradient and co-efficient of skin friction.

We compute the wall velocity in the MSSM. We therefore generalize the SM equations of motion for bubble walls moving through a hot plasma at the electroweak phase transition and calculate the friction terms which describe the viscosity of the plasma. We give the general expressions and apply them to a simple model where stops, tops and W bosons contribute to the friction. In a wide range of par...

The main purpose of this paper is to compare the predictions of four laws currently used for the estimation of the wall shear stress in an incompressible turbulent boundary layer-viz., A proposal is also made for a modified skin-friction law which would appear to predict values of the wall shear stress to within about 5 percent over its range of validity. A feature of this new law is that close...

th Australasian Fluid Mechanics Conference Monash University Melbourne Australia December A new laser interferometry skin friction meter was built and was used to measure skin friction in a series of turbulent boundary layer ows This method has the advantage of providing a direct measure of skin friction through thin lm lubrication theory It does not rely on the existence of a law of the wall o...

Calculation of lateral earth pressure on retaining walls is one of the main issues in geotechnics. The upper and lower bound theorems of plasticity are used to analyze the stability of geotechnical structures include bearing capacity of foundations, lateral earth pressure on retaining walls and factor of safety of slopes. In this paper formulation of finite element limit analysis is introduced ...

An instantaneous streamwise velocity perturbation of a new simulation turbulent channel flow at an unprecedented friction Reynolds number 10000 is conducted. One point statistics and budgets are discussed, solving some questions raising ones.

In this paper, we derive mathematical formulas for the skin friction coefficient in wall-bounded turbulence based on Reynolds averaged streamwise momentum equation and total stress. Specifically, with a theoretical or empirical relation of stress, is expressed terms mean velocity shear stress an arbitrary wall-normal region $$[h_0, h_1]$$ . The are validated using direct numerical simulation da...