Search results for "Flow velocity"
showing 10 items of 227 documents
The Effect of Tomography Imaging Artefacts on Structural Analysis and Numerical Permeability Simulations
2011
Fluid flow phenomena in porous materials can be found in many important processes in nature and in society. In particular, fluid flow through a porous medium contribute to several technological problems, e.g. extraction of oil or gas from porous rocks, spreading of contaminants in fluid-saturated soils and certain separation processes, such as filtration (Torquato, 2001). In paper and wood industry single and multi phase fluid flow properties in porous media play important roles related to manufacturing process and product development. The general laws describing creeping fluid flows are well known. However, a detailed study of fluid flow in porous heterogeneous media is complicated. This i…
In vivo investigations on microcirculatory disturbances induced by crenated erythrocytes following norepinephrine application
1974
Using a special apparatus for high resolution cinephotomicrography, which allows simultaneous observation and recording of microcirculatory changes, alterations in blood flow patterns and in red cell shape during norepinephrine acting have been studied. Under physiological conditions, and during slowing of capillary blood flow due to gradual removing of 20–25% of the circulating blood volume, the normal red cells are extremely deformable while passing through mesenteric capillaries. After application of norepinephrine a general arteriolar constrictive response in the bowel wall occurs, causing a further slowing of the capillary blood flow in the mesentery. Under these circumstances the eryt…
Testing the outflow theory of Malcherek by slit weir data
2018
Abstract In this paper the flow-process of a slit weir is analyzed by the outflow theory of Malcherek. Average flow velocity over the slit weir is expressed in terms of head over weir and the momentum correction coefficient. The theoretically deduced stage-discharge formula was then calibrated using experimental data obtained for a ratio between the weir and the channel width ranging from 0.05 to 0.25. The deduced stage–discharge relationship allows to measure discharge values characterized by errors which are, for 91% of the measured values, less than or equal to ± 5%.
The structure of steady, relativistic, magnetised jets with rotation
2015
We present equilibrium models of relativistic magnetised, infinite, axisymmetric jets with rotation propagating through an homogeneous, unmagnetised ambient medium at rest. The jet models are characterised by six functions defining the radial profiles of density, pressure, and the toroidal and axial components of velocity and magnetic field. Fixing the ambient pressure and the jet rest-mass density and axial components of the flow velocity and magnetic field, we analyze the influence of the toroidal magnetic field and several rotation laws on the structure of the equilibrium models. Our approach excludes by construction the analysis of the self-consistently magnetically launched jet models …
KINETICS OF CRYSTAL GROWTH LIMITED BY RANDOM VELOCITY FIELDS
2008
A spherical growth process controlled by velocity fluctuations of particles of a saturated solution is investigated. Velocity fluctuations are modeled by a Gaussian random field. The interface evolution is determined by a Langevin-type equation with a multiplicative random field, which in the case of the quasi-homogeneous random Gaussian field is equivalent to Fokker–Planck dynamics. We analyze numerically the Fokker–Planck equation and compare growth kinetics in the case of noisy (i.e. space-independent) fluctuations. It is shown that for a large class of spatially correlated velocity fluctuations, the growth kinetics is universal, i.e. it does not depend on the details of statistics of f…
The exact solution of the Riemann problem with non-zero tangential velocities in relativistic hydrodynamics
2000
We have generalised the exact solution of the Riemann problem in special relativistic hydrodynamics for arbitrary tangential flow velocities. The solution is obtained by solving the jump conditions across shocks plus an ordinary differential equation arising from the self-similarity condition along rarefaction waves, in a similar way as in purely normal flow. The dependence of the solution on the tangential velocities is analysed, and the impact of this result on the development of multidimensional relativistic hydrodynamic codes (of Godunov type) is discussed.
THE ACCELERATING JET OF 3C 279
2012
Analysis of the proper motions of the subparsec scale jet of the quasar 3C 279 at 15 GHz with the Very Long Baseline Array shows significant accelerations in four of nine superluminal features. Analysis of these motions is combined with the analysis of flux density light curves to constrain values of Lorentz factor and viewing angle (and their derivatives) for each component. The data for each of these components are consistent with significant changes to the Lorentz factor, viewing angle, and azimuthal angle, suggesting jet bending with changes in speed. We see that for these observed components Lorentz factors are in the range Γ = 10-41, viewing angles are in the range = 0.°1-5.°0, and in…
Coupled fluid-flow and magnetic-field simulation of the Riga dynamo experiment
2006
Magnetic fields of planets, stars, and galaxies result from self-excitation in moving electroconducting fluids, also known as the dynamo effect. This phenomenon was recently experimentally confirmed in the Riga dynamo experiment [ A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000) ; A. Gailitis et al., Physics of Plasmas 11, 2838 (2004) ], consisting of a helical motion of sodium in a long pipe followed by a straight backflow in a surrounding annular passage, which provided adequate conditions for magnetic-field self-excitation. In this paper, a first attempt to simulate computationally the Riga experiment is reported. The velocity and turbulence fields are modeled by a finite-volume Navi…
Entropic approach to estimate the mean flow velocity: experimental investigation in laboratory flumes
2015
The paper deals with the linear entropic relationship between the maximum velocity, u max , and the mean flow velocity, u m , through a dimensionless parameter Φ(M), in open-channel flow. The analysis is conducted with the aid of experimental data collected in straight laboratory flumes under different bed and side-walls roughness conditions. In particular, rough/vegetated beds and smooth/rough side-walls conditions have been investigated. The results show that, in the investigated conditions (with exception of low-submergence vegetated bed—h/k v < 2), Φ(M) can be assumed equal to a value that is very close to that found in natural channels. This demonstrates that Φ(M) is able to implicitl…
Role of secondary circulation on bank erosion in a large amplitude meandering laboratory channel
2009
This paper reports peculiar results of experimental investigation on the evolution of flow secondary circulation motion along a meander wave. The experiments have been conducted in a large amplitude meandering laboratory channel for two values of the width-to-depth ratio. Attention is focalised on how secondary motion affects the bank shear stress distribution, influencing the bank stability. The analysis essentially highlights that, especially for small width-to-depth ratio, as the channel curvature increases besides the classical central-region secondary circulation cell a counter-rotating circulation cell forms in the outer-bank region. Such counterrotating circulation cell allows to obt…