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Plasma-etching is a powerful tool in the determination of the resistance of the sublayer of skinned asymmetric hollow fiber membranes of poly (2,6-dimethyl-1,4-phenylene oxide). Using a resistance model and data provided by etched hollow PPO fiber membranes it is possible to predict the ultimate selectivity of the total membrane for helium over nitrogen and oxygen over nitrogen. From this model...

Once the first initial ripples have developed, they form according to actual flow forces and sediment properties. In this paper, a semianalytical approach determine length of developed is presented. The theory assumes disturbances at bed surface corresponding separations resulting from an individual respective boundary layer. What causes rhythmic perturbations not subject paper. Based on layer ...

Processing the data from a large variety of zero-pressure-gradient boundary layer flows shows that the Reynolds-number-dependent scaling law, which the present authors obtained earlier for pipes, gives an accurate description of the velocity distribution in a selfsimilar intermediate region of distances from the wall adjacent to the viscous sublayer. The appropriate length scale that enters the...

to Turbulence and Scalar Transport in Roughness Sub-layers SPATIAL HOMOGENEITY IN THE FOREST ROUGHNESS SUBLAYER? Ebba Dellwik, Sven-Erik Gryning, Ferhat Bingöl & Jakob Mann Risø National Laboratory For forested surfaces, the roughness sublayer is defined as a layer with enhanced eddy diffusivity compared to inertial sublayer scaling (e.g. Cellier and Brunet, 1992). In urban areas, the roughness...

The results of the experimental studies efficiency method vortex feeding polymers developed by authors are presented. novelty device lies in fact that when polymer is fed into boundary layer, longitudinal velocity and additional circumferential reported simultaneously. It has been established with introduction polyethylene oxide solutions layer model, using proposed device, a reduction hydrodyn...

In this work, exploratory numerical simulations of liquid–gas flows in horizontal pipes are conducted for three different sets of conditions in the annular and stratified-annular flow regimes. Careful dimensional analysis is used to choose governing parameters in a way that yields flows that are relevant to realistic engineering applications, while remaining computationally tractable. Statistic...

The behaviour of fluid-particle acceleration in near-wall turbulent flows is investigated in numerically simulated turbulent channel flows at low to moderate Reynolds numbers, Reτ =180∼ 600. The acceleration is decomposed into pressure-gradient (irrotational) and viscous contributions (solenoidal acceleration) and the statistics of each component are analysed. In near-wall turbulent flows, the ...

Long time simulations of the dispersion prolate spheroids in a turbulent channel are performed to study effect averaging procedure on particle statistics. The flow at Reτ=180 is directly simulated (DNS) and 300000 ellipsoids, modelled as point-particles tracked produce After long time, an initially uniform distribution reaches steady state which almost all particles segregated viscous sublayer....

We investigate a sequence of low-dimensional models of turbulent channel flows. These models are based on the extraction of the Karhunen–Loève (KL) eigenfunctions from a large-scale simulation in a wide channel with R∗ = 180 (based on the friction velocity). KL eigenfunctions provide an optimal coordinate system in which to represent the dynamics of the turbulent flow. The hierarchy of KL modes...