Effect of Velocity Distribution and Reynolds Number on the Diffusion Inhibition of Coaxial Jets

2021 ◽  
Vol 2021.74 (0) ◽  
pp. A32
Author(s):  
Kazuki HONDA ◽  
Suguru WAKABAYASHI ◽  
Rintaro YAMASHITA ◽  
Fujio AKAGI
Keyword(s):  
Reynolds Number ◽  
Velocity Distribution ◽  
Coaxial Jets

Analysis of Transitional Flow in Tube Based on PIV

2014 ◽  
Vol 574 ◽  
pp. 485-488
Author(s):  
Jun Wang ◽  
Guang Sheng Du ◽  
Yong Hui Liu
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Flow Field ◽  
Velocity Distribution ◽  
Axial Velocity ◽  
Transitional Flow ◽  
Experimental Result ◽  
Fluid Field ◽  
Normal Speed

In order to get the situation of transitional flow in tube, we tested the fluid field by PIV experiment and acquired the velocity distribution of the flow field at different Reynolds number (Re=2400 and Re=3000). At the same time the structure and characteristics of the flow field were obtained. The experimental result shows that the change of axial velocity in boundary layer is not obvious at low Reynolds number, the fluctuation of axial velocity appears and normal speed changes a little in mainstream area. With the increase of Reynolds number the axial velocity both in boundary layer and mainstream area change obviously, pulsation of the normal speed increases, the state of fluid flow gradually evolves from laminar to transitional flow.

Strouhal numbers of rectangular cylinders

1982 ◽  
Vol 123 ◽  
pp. 379-398 ◽  
Author(s):  
Atsushi Okajima
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Velocity Distribution ◽  
Flow Pattern ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Water Tank ◽  
Height Ratio ◽  
Rectangular Cylinders ◽  
Good Agreement

Experiments on the vortex-shedding frequencies of various rectangular cylinders were conducted in a wind tunnel and in a water tank. The results show how Strouhal number varies with a width-to-height ratio of the cylinders in the range of Reynolds number between 70 and 2 × l04. There is found to exist a certain range of Reynolds number for the cylinders with the width-to-height ratios of 2 and 3 where flow pattern abruptly changes with a sudden discontinuity in Strouhal number. The changes in flow pattern corresponding to the discontinuity of Strouhal number have been confirmed by means of measurements of velocity distribution and flow visualization. These data are compared with those of other investigators. The experimental results have been found to show a good agreement with those of numerical calculations.

FLOW FORMS IN A CHANNEL OF SMALL EXPONENTIAL DIVERGENCE

1934 ◽  
Vol 11 (6) ◽  
pp. 770-779 ◽  
Author(s):  
G. N. Patterson
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Initial Velocity ◽  
Reynolds Numbers ◽  
Transitional Region ◽  
Empirical Equations ◽  
Initial Velocity Distribution ◽  
General Flow ◽  
Theoretical Considerations

The motion of air through a channel of small exponential divergence has been investigated experimentally. A flow form derived by Blasius from theoretical considerations has been shown to exist in the range [Formula: see text] for the Reynolds number. The dependence of the general flow form on the initial velocity distribution where the divergence begins has been studied. It has been found that when this initial velocity distribution is parabolic, indicating a laminar motion in the throat of the channel, the flow form is symmetrical. Further investigations have shown that when the initial velocity distribution indicates that the motion near the walls in the throat of the channel lies in the transitional region between a laminar and a turbulent flow, then the flow form is unsymmetrical. Empirical equations have been obtained which give (1) the initial velocity distribution in the transitional region at R = 75.1, and (2) the motion near the walls where the divergence begins for Reynolds numbers lying in the range [Formula: see text].

Experimental determination of the main features of the viscous flow in the wake of a circular cylinder in uniform translation. Part 1. Steady flow

1977 ◽  
Vol 79 (2) ◽  
pp. 231-256 ◽  
Author(s):  
Madeleine Coutanceau ◽  
Roger Bouard
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Velocity Distribution ◽  
Viscous Flow ◽  
Experimental Determination ◽  
Geometrical Parameters ◽  
Visualization Method ◽  
Number Range ◽  
Hydrodynamic Field

A visualization method is used to obtain the main features of the hydrodynamic field for flow past a circular cylinder moving at a uniform speed in a direction perpendicular to its generating lines in a tank filled with a viscous liquid. Photographs are presented to show the particular fineness of the experimental technique. More especially, the closed wake and the velocity distribution behind the obstacle are investigated; the changes in the geometrical parameters describing the eddies with Reynolds number (5 < Re < 40) and with the ratio λ between the diameters of the cylinder and tank are given. A comparison with existing numerical and experimental results is presented and some remarks are made about the calculation techniques proposed up to the present. The limits of the Reynolds-number range for which the twin vortices exist and adhere stably to the cylinder are determined.

The Discharge Coefficient of a Planar Submerged Slit-Jet

2003 ◽  
Vol 125 (4) ◽  
pp. 613-619 ◽  
Author(s):  
S. K. Ali ◽  
J. F. Foss
Keyword(s):  
Reynolds Number ◽  
Velocity Distribution ◽  
Excellent Agreement ◽  
Potential Flow ◽  
Discharge Coefficient ◽  
Strong Dependence ◽  
Streamwise Velocity ◽  
Exit Plane ◽  
Nozzle Design ◽  
Wide Range

The discharge coefficient, CD, of a planar, submerged slit-jet has been determined experimentally over a relatively wide range of Reynolds number values: Re=100-6500, where the slit width (w) and the average streamwise velocity (〈U〉) at the exit plane are used to define the Reynolds number. The CD values exhibit a strong dependence on Re for Re<800. For Re>3000,CD achieves an apparent asymptotic value of 0.687 for the present nozzle design. This value is about 12% higher than the potential flow value. In contrast, the velocity distribution along the centerline was in excellent agreement with that of the potential flow solution. The experimental techniques that were used to evaluate the CDRe values, their numerical values, the corresponding uncertainties, and the possible influence of the geometrical design of the nozzle on the results are presented.

Reynolds number effects on the fluctuating velocity distribution in wall-bounded shear layers

2016 ◽  
Vol 28 (1) ◽  
pp. 015302 ◽  
Author(s):  
Wenfeng Li ◽  
Dorothee Roggenkamp ◽  
Wilhelm Jessen ◽  
Michael Klaas ◽  
Wolfgang Schröder
Keyword(s):  
Reynolds Number ◽  
Velocity Distribution ◽  
Shear Layers ◽  
Reynolds Number Effects

scholarly journals PIV-Measurements of Centrifugal Instabilities in a Rectangular Curved Duct with a Small Aspect Ratio

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 184
Author(s):  
Afshin Goharzadeh ◽  
Peter Rodgers
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Velocity Distribution ◽  
Channel Wall ◽  
Secondary Flows ◽  
Working Fluid ◽  
Measured Velocity ◽  
Outer Channel ◽  
Dean Vortices ◽  
Curved Duct

In this study, experimental measurements were undertaken using non-intrusive particle image velocimetry (PIV) to investigate fluid flow within a 180° rectangular, curved duct geometry of a height-to-width aspect ratio of 0.167 and a curvature of 0.54. The duct was constructed from Plexiglas to permit optical access to flow pattern observations and flow velocity field measurements. Silicone oil was used as working fluid because it has a similar refractive index to Plexiglas. The measured velocity fields within the Reynolds number ranged from 116 to 203 and were presented at the curved channel section inlet and outlet, as well as at the mid-channel height over the complete duct length. It was observed from spanwise measurements that the transition to unsteady secondary flows generated the creation of wavy structures linked with the formation of Dean vortices close to the outer channel wall. This flow structure became unsteady with increasing Reynolds number. Simultaneously, the presence of Dean vortices in the spanwise direction influenced the velocity distribution in the streamwise direction. Two distinct regions defined by a higher velocity distribution were observed. Fluid particles were accelerated near the inner wall of the channel bend and subsequently downstream near the outer channel wall.

scholarly journals Featuresof velocity distribution in a turbulent flow

Vestnik MGSU ◽  
2015 ◽  
pp. 103-109
Author(s):  
Valeriy Stepanovich Borovkov ◽  
Valeriy Valentinovich Volshanik ◽  
Irina Aleksandrovna Rylova
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Velocity Profile ◽  
Turbulent Flow ◽  
Velocity Distribution ◽  
Drag Coefficient ◽  
Viscous Flow ◽  
Measured Velocity ◽  
Displacement Thickness ◽  
Logarithmic Velocity Profile

In this article the questions of kinematic structure of steady turbulent flow near a solid boundary are considered. It has been established that due to friction the value of the local Reynolds number decreases and always becomes smaller than the critical value of the Reynolds number, which leads to formation of viscous flow near a wall. Velocity profiles for the area of viscous flow with constant and variable shear stress are obtained. The experimental investigations of different authors showed that in this area the flow is of unsteady character, where viscous flow occurs intermittently with turbulent flow. With increasing distance from the wall the flow becomes fully turbulent. In the area where generation and dissipation of turbulence are very intensive, there is a developed turbulent flow with increasing distance from the wall. Dissipation of turbulence is an action of viscous force. The logarithmic velocity profile was obtained by L. Prandtl disregarding the viscous component and the linear variation of the shear stress in the depth flow. The profile parameters C and k were determined from Nikuradze’s experiments. The detailed investigations of Nikuradze’s experiments established the part of the flow where the logarithmic velocity profile is correctly confirmed.This part of the flow was called “Prandtl layer”. The measured velocity distribution above this layer deviates in the direction of greater values. Processing of experimental data revealed that the thickness of the “Prandtl layer”, normalized to the radius of a pipe, depend on a drag coefficient. The formula for determining the thickness of the “Prandtl layer” with the known value of the drag coefficient is obtained. It is shown that the thickness of “Prandtl layer” almost coincides with the boundary layer displacement thickness formed on the wall of the pipe.

An Experimental Investigation of Cavitation Inception and Development on a Two-Dimensional Hydrofoil

2000 ◽  
Vol 44 (04) ◽  
pp. 259-269
Author(s):  
J.-A. Astolfi ◽  
J.-B. Leroux ◽  
P. Dorange ◽  
J.-Y. Billard ◽  
F. Deniset ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Velocity Distribution ◽  
Cavity Length ◽  
Pressure Coefficient ◽  
Sudden Change ◽  
Leading Edge ◽  
Cavitation Number ◽  
Cavity Surface ◽  
Cavitation Inception ◽  
Flow Visualizations

The cavitation inception (and desinent) angles at given cavitation numbers, the velocity distribution, and the resulting pressure coefficient, together with the sheet cavity lengths developing on a hydrofoil surface, have been investigated experimentally for a Reynolds number ranging between 0.4 × 106 and 1.2 × 106. It is shown that the cavitation inception (and desinent) angle decreases progressively when the Reynolds number increases and tends to be close to the theoretical (inviscid) value when the Reynolds number is larger than 0.8 × 106. The magnitude and the position of the minimum surface pressure coefficient, inferred from the velocity distribution measured at the leading edge, were shown to be dependent upon the Reynolds number as well. An investigation of the cavitating flow velocity field upstream of the cavity and on the cavity surface showed that the pressure in the cavity was very close to the vapor pressure. The detachment location of the cavity was found to occur very close to the leading edge (at about one hundredth of the foil chord for both Re = 0.4 × 10® and Re = 0.8 × 106). The length cavities measured from flow visualizations exhibited a sudden change for a Reynolds number passing from 0.7 × 106 to 0.8 × 106 with a given angle of incidence (α= 6 deg) and cavitation number (σ = 1.3). Photographs of the sheet cavity show that the cavity length can be inferred also from the extent of the region for which the pressure coefficient is close to the cavitation number. It was shown to have the values l/c 0.03 for Re = 0.4 × 106 and l/c ~ 0.06 for Re = 0.8 × 10® and σ = 1.8 with the latter value very close to the value obtained from flow visualizations. Photographs of the cavity show that the increase of the cavity length is coupled to the migration, towards the leading edge, of a transition point on the cavity surface when the Reynolds number increases.

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