Written in English
|The Physical Object|
|Number of Pages||206|
Using Coles additive law of the wall and law of the wake, with constant shift allowed for the effect of roughness, an integral method of analysis is put forward for evaluating the characteristic parameters (friction, wake and roughness parameters) from experimental mean velocity data of rough-wall turbulent boundary layers in zero pressure by: The turbulent characteristics of the neutral boundary layer developing over rough surfaces are not well predicted with operational weather-forecasting models. The problem is attributed to inadequate mixing-length models, to the anisotropy of the flow and to a lack of controlled experimental data against which to validate numerical studies. Therefore, in order to address directly the modelling Cited by: 8. Wind tunnel measurements of turbulent boundary layers over three-dimensional rough surfaces have been carried out to determine the critical roughness height beyond which the roughness affects the. Under an Elsevier user license. open archive. Abstract. The influence of surface roughness in the prediction of the mean flow and turbulent properties of a high-speed supersonic (M = , Re/m = 2 × ) turbulent boundary layer flow over a flat plate is numerically investigated.
All the above studies are for the flow visualization over the smooth surfaces, but there are only few studies for the flow visualization over the rough or grooved surfaces. Du and Tong  had carried out experiments for the turbulent thermal convection in a cylindrical cell containing water with pyramidical rough elements of height mm. Comparison of turbulent boundary layers over smooth and rough surfaces up to high Reynolds numbers - Volume - D. T. Squire, C. Morrill-Winter, N. Hutchins, M. P. In fact, the boundary layer velocity profile of turbulent flow over a flat plate (zero pressure gradients) has a larger velocity gradient at the wall since it is much fuller than the one in the laminar flow. This leads to have greater skin friction along the surface in the turbulent flow. Coherent Motions in the Turbulent Boundary Layer S K Robinson Annual Review of Fluid Mechanics Boundary-Layer Transition I Tani Annual Review of Fluid Mechanics Turbulent Boundary-Layer Separation R L Simpson Annual Review of Fluid Mechanics High–Reynolds Number Wall Turbulence Alexander J. Smits, Beverley J. McKeon, and Ivan Marusic.
The influence of three-dimensional, stochastic roughness on the properties of turbulent boundary layers has been investigated experimentally in order to obtain an improved understanding and description of such effects on the boundary-layer flow over turbomachinery blading. Four rough surfaces were examined: a surface representative of newly-finished turbo-machinery blading, a variant of this surface with different roughness parameters, a sand-cast surface and a mesh surface . Recent observations of flux-gradient anomalies in atmospheric flow close to forests, and similar rough surfaces, prompted a wind-tunnel investigation in which cross-wire anemometry was used to study the vertical development and horizontal variability of adiabatic flow over five regularly arrayed rough surfaces, encompassing a fold range of roughness concentration λ. The methods listed above [22, 13, 14, 18] all assume that the viscous scaled mean velocity proﬁle U+(z+)for the devel- oping turbulent boundary layer over the rough wall, is similar to that of the smooth wall but with an additional downwards shift ∆U+=f(k+ s)known as the Hama roughness function. The results of an experimental investigation into the steady-state plane turbulent boundary layer in an incompressible liquid at an impermeable wall are presented. Cases of flow at smooth and rough surfaces in the presence of a longitudinal pressure gradient are considered. The results of measurements of the turbulent structure of the flow at various distances from the channel inlet are .