Effect of small asymmetries on axisymmetric stenotic flow

2013 ◽  
Vol 721 ◽  
Author(s):  
Martin D. Griffith ◽  
Thomas Leweke ◽  
Mark C. Thompson ◽  
Kerry Hourigan
Keyword(s):  
Velocity Profile ◽  
Experimental Test ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Machining Precision ◽  
Severe Effect ◽  
Highly Sensitive ◽  
Flow Through ◽  
Simulated Flow

AbstractFlow through axisymmetric and eccentric sinuous stenoses is investigated numerically, for Reynolds numbers up to 400. The eccentricity consists of an offset of the stenosis throat. A range of stenosis eccentricity is tested; the wake flow is found to be highly sensitive to small eccentricities in the stenosis geometry, even with stenosis offsets of the order of the machining precision of experimental test-sections. Comparisons are made between the numerically simulated flow through stenoses with small eccentricities and results from the literature of non-axisymmetric flows through nominally axisymmetric geometries. The effect of distortion to the inlet Poiseuille velocity profile is also investigated and found to have a significantly less severe effect on the downstream wake flow than geometric eccentricity.

Flow in a rotating non-aligned straight pipe

1984 ◽  
Vol 144 ◽  
pp. 297-310 ◽  
Author(s):  
J. Berman ◽  
L. F. Mockros
Keyword(s):  
Velocity Profile ◽  
Axial Velocity ◽  
Reynolds Numbers ◽  
Straight Pipe ◽  
Regular Perturbation ◽  
Axial Velocity Profile ◽  
Axial Profile ◽  
Flow Through ◽  
Effects Of Rotation ◽  
Two Parameters

A third-order regular perturbation solution is developed for laminar flow through a straight pipe that is rotating about an axis not aligned with the pipe axis. Coriolis accelerations produce transverse secondary velocities (similar to those in flow through coiled tubes) and modify the axial-velocity profile. The effects of rotation on the velocity fields are shown to depend on two parameters: (i) the product of axial and rotational Reynolds numbers, and (ii) the square of the rotational Reynolds number itself. Even though their strength increases with increases in parameter magnitudes, transverse circulations are qualitatively insensitive to parametric values. The axial profile, on the other hand, can be significantly modified by the rotation; the zeroth-order parabolic axial profile can be skewed toward the outside, dimpled in the centre with maximums on either side of the centreline, or both, depending on the values of the two parameters. The modification of the axial-velocity profile has important ramifications in the design of heat/mass-transfer devices.

CFD Simulation of Fluid Flow Through Porous Media: Application to Decomposed Gases Flow Through Foam Pattern in Lost Foam Casting

Materials ◽  
2003 ◽  
Author(s):  
Sayavur I. Bakhtiyarov ◽  
Ruel A. Overfelt
Keyword(s):  
Cfd Simulation ◽  
Reynolds Numbers ◽  
Phase Flow ◽  
Flow Through Porous Media ◽  
Foam Material ◽  
Element Analysis ◽  
Wide Range ◽  
Flow Through ◽  
Foam Pattern ◽  
Lost Foam

Numerical simulation of decomposed gases through foam pattern was conducted using finite element analysis. A new kinetic model is proposed for gaseos phase flow between molten metal and foam material. The computations were performed for a wide range of Reynolds numbers. The results of the simulations are compared with the experiemental data obtained in this study.

Experimental Investigation of Subsonic Turbulent Flow Over Single and Double Backward Facing Steps

1962 ◽  
Vol 84 (3) ◽  
pp. 317-325 ◽  
Author(s):  
D. E. Abbott ◽  
S. J. Kline
Keyword(s):  
Experimental Investigation ◽  
Velocity Profile ◽  
Flow Pattern ◽  
Reynolds Numbers ◽  
Area Ratio ◽  
Single Step ◽  
Reattachment Length ◽  
Double Step ◽  
Wide Range ◽  
Geometric Variables

Results are presented for flow patterns over backward facing steps covering a wide range of geometric variables. Velocity profile measurements are given for both single and double steps. The stall region is shown to consist of a complex pattern involving three distinct regions. The double step contains an assymmetry for large expansions, but approaches the single-step configuration with symmetric stall regions for small values of area ratio. No effect on flow pattern or reattachment length is found for a wide range of Reynolds numbers and turbulence intensities, provided the flow is fully turbulent before the step.

Heat and mass transfer effects on MHD non-Newtonian fluids flow through an inclined thermally-stratified porous medium

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Gladys Tharapatla ◽  
Pamula Rajakumari ◽  
Ramana G.V. Reddy
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Velocity Profile ◽  
Heat And Mass Transfer ◽  
Newtonian Fluids ◽  
Transfer Effects ◽  
Content Type ◽  
Non Linear ◽  
Homotopy Analysis ◽  
Flow Through

Purpose This paper aims to analyze heat and mass transfer of magnetohydrodynamic (MHD) non-Newtonian fluids flow past an inclined thermally stratified porous plate using a numerical approach. Design/methodology/approach The flow equations are set up with the non-linear free convective term, thermal radiation, nanofluids and Soret–Dufour effects. Thus, the non-linear partial differential equations of the flow analysis were simplified by using similarity transformation to obtain non-linear coupled equations. The set of simplified equations are solved by using the spectral homotopy analysis method (SHAM) and the spectral relaxation method (SRM). SHAM uses the approach of Chebyshev pseudospectral alongside the homotopy analysis. The SRM uses the concept of Gauss-Seidel techniques to the linear system of equations. Findings Findings revealed that a large value of the non-linear convective parameters for both temperature and concentration increases the velocity profile. A large value of the Williamson term is detected to elevate the velocity plot, whereas the Casson parameter degenerates the velocity profile. The thermal radiation was found to elevate both velocity and temperature as its value increases. The imposed magnetic field was found to slow down the fluid velocity by originating the Lorentz force. Originality/value The novelty of this paper is to explore the heat and mass transfer effects on MHD non-Newtonian fluids flow through an inclined thermally-stratified porous medium. The model is formulated in an inclined plate and embedded in a thermally-stratified porous medium which to the best of the knowledge has not been explored before in literature. Two elegance spectral numerical techniques have been used in solving the modeled equations. Both SRM and SHAM were found to be accurate.

Investigation of the Flow at the Exit of an Unshrouded Centrifugal Impeller and Comparison With the “Classical” Jet-Wake Theory

1991 ◽  
Vol 113 (4) ◽  
pp. 654-659 ◽  
Author(s):  
K.-H. Rohne ◽  
M. Banzhaf
Keyword(s):  
Velocity Profile ◽  
Centrifugal Compressor ◽  
Wake Flow ◽  
Centrifugal Impeller ◽  
Uniform Velocity ◽  
Thermodynamic Measurements

L2F measurements of the flow at the exit of modern unshrouded centrifugal impellers with backswept blades yield a much more uniform velocity profile compared to former measurements on impellers with radial blading. Further evaluations show that the “classical” jet-wake theory assuming an isentropic jet and a wake flow congruent with the shape of the blade at the impeller exit needs correction in order to obtain meaningful results when interpreting thermodynamic measurements on centrifugal compressor stages.

Effects of Applied Acoustic Fields on Attached Jet Flows

1971 ◽  
Vol 93 (1) ◽  
pp. 63-73 ◽  
Author(s):  
Donald O. Rockwell ◽  
Kenji Toda
Keyword(s):  
Reynolds Numbers ◽  
Jet Flows ◽  
Design Criteria ◽  
Arc Length ◽  
Hot Wire ◽  
Applied Frequency ◽  
Smoke Visualization ◽  
The Third ◽  
Severe Effect ◽  
Jet Nozzle

The effects of application of sound of a spectrum of frequencies and amplitudes to bounded attached jets of a range of Reynolds numbers flowing over surfaces of various radii of curvature have been examined using hot-wire anemometry, smoke visualization, and tuft-deflection techniques. Frequencies of sound to which the jet is sensitive, results of changes in sound amplitude at a given frequency, and the growth of the effects of applied sound with arc length from the nozzle exit were investigated to provide some qualitative design criteria for controlling the sensitivity of flueric elements to externally applied sound. Frequencies of sound which are related to the jet nozzle resonance characteristics have the most severe effect on the attached jet. For a given applied frequency, the flow field of the jet can be altered for a much wider range of jet Reynolds number at higher amplitudes of applied sound than at relatively low amplitudes of applied sound. Four Reynolds numbers regimes can be established to describe the behavior of the attached jet with applied sound, Frequency- and amplitude-dependent jumps in angle of detachment of the jet are attainable in the first two regimes, and deflections of the jet proportional to the applied frequency and amplitude are attainable in the third and fourth regimes.

Steady Laminar Flow through Twisted Pipes: Fluid Flow in Square Tubes

1981 ◽  
Vol 103 (4) ◽  
pp. 785-790 ◽  
Author(s):  
J. H. Masliyah ◽  
K. Nandakumar
Keyword(s):  
Laminar Flow ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Dissipation Term ◽  
Axial Velocity Profile ◽  
Secondary Motion ◽  
Qualitative Nature ◽  
Flow Through ◽  
Steady Laminar

The Navier-Stokes equation in a rotating frame of reference is solved numerically to obtain the flow field for a steady, fully developed laminar flow of a Newtonian fluid in a twisted tube having a square cross-section. The macroscopic force and energy balance equations and the viscous dissipation term are presented in terms of variables in a rotating reference frame. The computed values of friction factor are presented for dimensionless twist ratios, (i.e., length of tube over a rotation of π radians normalized with respect to half the width of tube) of 20, 10, 5 and 2.5 and for Reynolds numbers up to 2000. The qualitative nature of the axial velocity profile was observed to be unaffected by the swirling motion. The secondary motion was found to be most important near the wall.

The Effects of Fish Cages on Ambient Currents

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Lars C. Gansel ◽  
Thomas A. McClimans ◽  
Dag Myrhaug
Keyword(s):  
Drag Force ◽  
Particle Image ◽  
Reynolds Numbers ◽  
Strain Gauges ◽  
Metal Mesh ◽  
Image Velocimetry ◽  
Flow Through ◽  
Fish Cages ◽  
Ambient Currents ◽  
Wake Characteristics

Experiments were carried out to measure forces on and wake characteristics downstream from fish cages. Cylinders made from metal mesh with porosities of 0%, 30%, 60%, 75%, 82%, and 90% were tested in a towing tank. The drag force was measured with strain gauges, and the flow field downstream from the models was analyzed using particle image velocimetry. The Reynolds numbers ranged from 1000–20,000 based on the model diameter and 15–300 based on the diameter of the strings of the mesh as an independent obstacle. High porosities (here, 82% and 90%) lead to low water blockage and allow a substantial amount of water to flow through the model. The data indicate that the wake characteristics change toward the wake characteristics of a solid cylinder at a porosity just below 75%. The drag force is highly dependent on the porosity for high porosities of a cylinder.

scholarly journals Near-Wake Observations behind Azimuthally Perforated Disks With Varying Hole Layout and Porosity in Smooth Airstreams at High Reynolds Numbers

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Raf Theunissen ◽  
Robert Worboys
Keyword(s):  
Drag Coefficient ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Mean Flow ◽  
Flow Topology ◽  
Near Wake ◽  
Two Component ◽  
High Reynolds ◽  
Component Particle

Porous disks are commonly encountered in experimental studies dealing with flow through objects such as wind turbines, parachutes, and fluidic devices to regulate pressure and/or downstream turbulence. Perforations are typically staggered and only porosity is altered to attain the required disk drag coefficient, despite a documented influence of topology. Few works have reported, however, to which extent the spatial distribution of the circular perforations affect the mean flow pertaining freestanding disks, and for this reason, this work presents a first, more systematic study focused on the effect of azimuthally varying hole topology and porosity on disk drag and near-wake characteristics. An experimental study performed in airflows of negligible freestream turbulence at Reynolds numbers in the order of 105 is reported and related to the existing literature to ensure reliability. Complementary to drag measurements, near-wake surveys have been performed on a variety of perforation layouts using two-component laser Doppler velocimetry and two-component particle image velocimetry. It is shown that minor changes in perforations can cause drastic changes in near-wake flow topology and no perforation layout can be consistently associated with highest drag. Explicit empirical expressions for drag coefficient linked with the simplified topologies considered have been derived.

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