Dissipation and Cavitation Characteristics of Single-Hole Orifices

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Stefano Malavasi ◽  
Gianandrea Vittorio Messa
Keyword(s):  
Reynolds Number ◽  
Pressure Coefficient ◽  
Diameter Ratio ◽  
Incoming Flow ◽  
Relative Thickness ◽  
Self Similarity ◽  
Pressure Losses ◽  
Geometrical Characteristics ◽  
Flow Parameters ◽  
Flow Through

The purpose of this work is to study the dependence of the pressure losses through sharp-edged orifices with respect to the most significant parameters and to find an efficient way to check whether cavitation is likely to occur. Computational fluid dynamics was used to simulate the flow through orifices with different geometrical characteristics for various incoming flow velocities. In particular, the diameter ratio was varied between 0.39 and 0.70, the relative thickness between 0.30 and 1.40, and the pipe Reynolds number between 3.85 × 104 and 1.54 × 105. The computed pressure drop coefficient in the region of self-similarity with respect to the pipe Reynolds number was first compared to that obtained from some literature models. Afterwards, the comparison with experimental data revealed that an extended pressure criterion is suitable to predict the presence of cavitating conditions. A dimensionless minimum pressure coefficient was then defined, and its dependence upon the above mentioned geometrical and flow parameters was investigated. Finally, a practical formula for the prediction of cavitation was provided.

scholarly journals Second-order Solutions for Steady Magnetohydrodynamic Channel Flow with Anisotropic Conductivity

1972 ◽  
Vol 25 (6) ◽  
pp. 719
Author(s):  
DM Panton
Keyword(s):  
Reynolds Number ◽  
Perturbation Expansion ◽  
Magnetic Reynolds Number ◽  
Arbitrary Cross Section ◽  
Second Order ◽  
Anisotropic Conductivity ◽  
Square Channel ◽  
Flow Parameters ◽  
Flow Through ◽  
Magnetohydrodynamic Channel

Further investigation of steady magnetohydrodynamic flow through a straight channel of arbitrary cross section with nonconducting walls is considered, in the presence of anisotropic conductivity due to the Hall effect, where no restriction is made on the Reynolds number or magnetic Reynolds number. An approximate solution is provided by a perturbation expansion in terms of the Hall parameter, assumed small. Corrections are made to the first-order solutions established by Panton and Hosking (1971) and the solutions are then extended to the second order for a square channel. It is found that both the Reynolds number and magnetic Reynolds number terms have a significant influence on the mass transport, the former far outweighing the contribution to the flow established by Tani (1962) for the values of the flow parameters assumed.

Local Pressure Measurement of Gaseous Flow Through Microchannels

1999 ◽  
Author(s):  
Stephen E. Turner ◽  
Hongwei Sun ◽  
Mohammad Faghri ◽  
Otto J. Gregory
Keyword(s):  
Reynolds Number ◽  
Pressure Distribution ◽  
Friction Factor ◽  
Knudsen Number ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Helium Flow ◽  
Local Pressure ◽  
Pressure Losses ◽  
Flow Through

Abstract This paper presents an experimental investigation on nitrogen and helium flow in microchannels etched in silicon with hydraulic diameters of 9.7, 19.6, and 46.6 μm, and Reynolds numbers ranging from 0. 2 to 1000. The objectives of this research are (1) to measure the pressure distribution along the length of a microchannel; and (2) to determine the friction factor within the fully developed region of the microchannel. The pressure distribution is presented as absolute local pressure plotted against the distance from the microchannel inlet. The friction factor results are presented as the product of friction factor and Reynolds number plotted against Reynolds number with the outlet Knudsen number, Kn, as a curve parameter. The following conclusions have been reached in the present investigation: (1) Pressure losses at the microchannel entrance can be significant; (2) the product, f*Re, when measured sufficiently far away from the entrance and exit is a constant in the laminar flow region; and (3) the friction factor decreases as the Knudsen number increases.

A Series Pressure Drop Representation for Flow Through Orifice Tubes

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
T. A. Jankowski ◽  
E. N. Schmierer ◽  
F. C. Prenger ◽  
S. P. Ashworth
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Simple Model ◽  
Pressure Drop ◽  
Diameter Ratio ◽  
Pressure Drops ◽  
In Series ◽  
Orifice Flow ◽  
Flow Through ◽  
Length To Diameter Ratio

A simple model is developed here to predict the pressure drop and discharge coefficient for incompressible flow through orifices with length-to-diameter ratio greater than zero (orifice tubes) over wide ranges of Reynolds number. The pressure drop for flow through orifice tubes is represented as two pressure drops in series; namely, a pressure drop for flow through a sharp-edged orifice in series with a pressure drop for developing flow in a straight length of tube. Both of these pressure drop terms are represented in the model using generally accepted correlations and experimental data for developing flows and sharp-edged orifice flow. We show agreement between this simple model and our numerical analysis of laminar orifice flow with length-to-diameter ratio up to 15 and for Reynolds number up to 150. Agreement is also shown between the series pressure drop representation and experimental data over wider ranges of Reynolds number. Not only is the present work useful as a design correlation for equipment relying on flow through orifice tubes but it helps to explain some of the difficulties that previous authors have encountered when comparing experimental observation and available theories.

Friction Factor for Flow in Rectangular Ducts With One Side Rib-Roughened

1994 ◽  
Vol 116 (3) ◽  
pp. 488-493 ◽  
Author(s):  
B. Youn ◽  
C. Yuen ◽  
A. F. Mills
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Software Package ◽  
Diameter Ratio ◽  
Numerical Results ◽  
Wall Function ◽  
Height Ratio ◽  
Aspect Ratios ◽  
Flow Through ◽  
Rib Roughened

Numerical simulations of incompressible turbulent flow through rectangular ducts with one side rib-roughened were performed to determine pressure drop. The “PHOENICS” software package was used for the computations, which required provision of a wall function for transverse rib-roughened surfaces. The present study was conducted in the range of 105≤ Reynolds number ≤ 107, 0.01 ≤ rib height to hydraulic diameter ratio ≤ 0.04, 10≤ pitch to rib height ratio ≤ 40. Using the numerical results, friction factor charts for various aspect ratios were generated. The numerical results agreed well with experimental data that was obtained for 105 < Reynolds number < 2 × 105. In addition, a scheme for predicting friction factor using existing correlations for smooth and rough walls was developed.

scholarly journals Theoretical Study of Compressible Flow through Aneurysms

2021 ◽  
Author(s):  
Maria Jumani
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Theoretical Study ◽  
Reynolds Numbers ◽  
Centerline Velocity ◽  
Flow Parameters ◽  
Flow Through ◽  
Wall Shear

The goal of this research is to analyze the effect of blood flow through expansions by using the KarmanPohlhausen method. The Karman-Pohlhausen method has previously been used in several research works to analyze the flow through constrictions. In this Thesis, the effect of different flow parameters (Reynolds number, compressibility, and slip) on pressure, pressure gradient, centerline velocity, and on wall shear stress are analyzed. Our results show that the pressure gradient curves are most affected by increasing Reynolds number and compressibility, as well as for smaller slip values (ws0). Furthermore, the scaled centerline velocity was least affected by varying Reynolds and Mach numbers, whereas changes are observed in centerline velocity curves for different slip values. The wall shear stress was essentially unchanged by the Reynolds numbers, compressibility range and slip values considered in this Thesis.

The Influence of the Wall on Flow Through Pipes Packed With Spheres

1990 ◽  
Vol 112 (1) ◽  
pp. 84-88 ◽  
Author(s):  
R. M. Fand ◽  
R. Thinakaran
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Porous Media ◽  
Turbulent Flow ◽  
Porous Matrix ◽  
Circular Cylinders ◽  
Empirical Equations ◽  
Flow Parameters ◽  
Flow Through ◽  
Dimension Ratio

This paper presents the results of an experimental investigation that is a sequel to a previously published study of the flow of fluids through porous media whose matrices are composed of randomly packed spheres. The objective of the previous study was to accurately determine the ranges of the Reynolds number for which Darcy, Forchheimer and turbulent flow occur, and also the values of the controlling flow parameters—namely, the Kozeny-Carman constant for Darcy flow and the Ergun constants for Forchheimer and turbulent flow—for porous beds that are infinite in extent; that is, practically speaking, for sufficiently large values of the dimension ratio, D/d, where D is a measure of the extent of the bed and d is the diameter of a single spherical particle of which the porous matrix is composed. The porous media studied in the previous and present experiments were confined within circular cylinders (pipes), for which the dimension D is taken to be the diameter of the confining cylinder. The previous study showed that the flow parameters are substantially independent of the dimension ration for D/d ≥ 40. For D/d < 40, the so-called “wall effect” becomes significant, and the flow parameters become functionally dependent upon this ratio. The present paper presents simple empirical equations that express the porosity and the flow parameters as functions of D/d for 1.4 ≤ D/d < 40. Transitions from one type to another were found to be independent of D/d and occur at values of the Reynolds number identical to those reported in the previous study.

Fluid Excitation Forces Acting on a Square Tube Array

1987 ◽  
Vol 109 (4) ◽  
pp. 415-423 ◽  
Author(s):  
S. S. Chen ◽  
J. A. Jendrzejczyk
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Incoming Flow ◽  
Test Results ◽  
Flow Conditions ◽  
Fluid Forces ◽  
System Components ◽  
Drag And Lift

Fluid forces acting on a tube array are important in the assessment of vibration of system components consisting of multiple circular cylinders. This paper presents test results for a square tube array with the pitch-to-diameter ratio of 1.75 subject to turbulent flow. The fluctuating drag and lift forces are measured as a function of Reynolds number, incoming flow conditions, and tube location in an array.

Calculation of incompressible flow past a circular cylinder at moderate Reynolds numbers

1969 ◽  
Vol 37 (1) ◽  
pp. 95-114 ◽  
Author(s):  
Robert Leigh Underwood
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Differential Equations ◽  
Incompressible Flow ◽  
Equations Of Motion ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Number Range ◽  
Flow Parameters ◽  
Flow Past

The steady, two-dimensional, incompressible flow past a circular cylinder is calculated for Reynolds numbers up to ten. An accurate description of the flow field is found by employing the semi-analytical method of series truncation to reduce the governing partial differential equations of motion to a system of ordinary differential equations which can be integrated numerically. Results are given for Reynolds numbers between 0.4 and 10.0 (based on diameter). The Reynolds number at which separation first occurs behind the cylinder is found to be 5.75. Over the entire Reynolds number range investigated, characteristic flow parameters such as the drag coefficient, pressure coefficient, standing eddy length, and streamline pattern compare favourably with available experimental data and numerical solution results.

Pressure-flow relationships in a collaterally ventilating dog lung segment

1983 ◽  
Vol 54 (4) ◽  
pp. 956-960 ◽  
Author(s):  
L. E. Olson ◽  
J. R. Rodarte ◽  
N. E. Robinson
Keyword(s):  
Reynolds Number ◽  
Lung Volume ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Pressure Losses ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Residual Capacity ◽  
Flow Through

We evaluated the pressure (P)-flow (V) relationship in collaterally ventilating dog lung segments by passing He, N2, and SF6 through a bronchoscope (5 mm OD) wedged in a peripheral airway. Measurements were made at functional residual capacity (FRC) and two higher lung volumes, keeping segment-to-airway opening pressure constant (3 cmH2O) in five anesthetized, paralyzed, vagotomized, supine dogs. Average flows ranged from 5.0 to 8.0 ml/s for He, 4.5 to 7.5 ml/s for N2, and 3.4 to 4.7 ml/s for SF6. When these data were fitted as P = K1/3/3 mu V + K2 rho V2, density-dependent pressure losses were unimportant when He and N2 were used, suggesting laminar flow with these gases. A dimensionless plot of the total pressure drop relative to a reference dynamic pressure as a function of Reynolds number at the bronchoscope tip suggested that flow through the segment behaved as if it were laminar at Reynolds numbers less than 100. Furthermore, when the airway diameter used to compute the normalized pressure and Reynolds number was scaled as the cubic root of lung volume, curves for all three gases were superimposed, suggesting that the dimensions of intrasegmental/collateral airways scale as lung volume 1/3.

scholarly journals Theoretical Study of Compressible Flow through Aneurysms

2021 ◽  
Author(s):  
Maria Jumani
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Pressure Gradient ◽  
Theoretical Study ◽  
Reynolds Numbers ◽  
Centerline Velocity ◽  
Flow Parameters ◽  
Flow Through ◽  
Wall Shear

The goal of this research is to analyze the effect of blood flow through expansions by using the KarmanPohlhausen method. The Karman-Pohlhausen method has previously been used in several research works to analyze the flow through constrictions. In this Thesis, the effect of different flow parameters (Reynolds number, compressibility, and slip) on pressure, pressure gradient, centerline velocity, and on wall shear stress are analyzed. Our results show that the pressure gradient curves are most affected by increasing Reynolds number and compressibility, as well as for smaller slip values (ws0). Furthermore, the scaled centerline velocity was least affected by varying Reynolds and Mach numbers, whereas changes are observed in centerline velocity curves for different slip values. The wall shear stress was essentially unchanged by the Reynolds numbers, compressibility range and slip values considered in this Thesis.

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