Reynolds Number Effects on the Performance Characteristic of a Small Regenerative Pump

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Shin-Hyoung Kang ◽  
Su-Hyun Ryu
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Internal Flow ◽  
Reynolds Numbers ◽  
Maximum Efficiency ◽  
Three Dimensional Flow ◽  
One Dimensional ◽  
Rotating Speed ◽  
Dimensional Modeling ◽  
Reynolds Number Effects

This paper studies the effect of the Reynolds number on the performance characteristics of a small regenerative pump. Since regenerative pumps have low specific speeds, they are usually applicable to small devices such as micropumps. As the operating Reynolds number decreases, nondimensional similarity parameters such as flow and head coefficients and efficiency become dependent on the Reynolds number. In this study, the Reynolds number based on the impeller diameter and rotating speed varied between 5.52×103 and 1.33×106. Complex three-dimensional flow structures of internal flow vary with the Reynolds numbers. The coefficients of the loss models are obtained by using the calculated through flows in the impeller. The estimated performances obtained by using one-dimensional modeling agreed reasonably well with the numerically calculated performances. The maximum values of flow and head coefficients depended on the Reynolds number when it is smaller than 2.65×105. The critical value of the Reynolds number for loss coefficient and maximum efficiency variations with Reynolds number was 1.0×105.

Pressure-driven flow in a channel with porous walls

2011 ◽  
Vol 679 ◽  
pp. 77-100 ◽  
Author(s):  
QIANLONG LIU ◽  
ANDREA PROSPERETTI
Keyword(s):  
Reynolds Number ◽  
Porous Medium ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Three Dimensional Flow ◽  
Porous Layers ◽  
Simple Cubic ◽  
Porous Walls ◽  
Pressure Driven Flow ◽  
Pressure Driven

The finite-Reynolds-number three-dimensional flow in a channel bounded by one and two parallel porous walls is studied numerically. The porous medium is modelled by spheres in a simple cubic arrangement. Detailed results on the flow structure and the hydrodynamic forces and couple acting on the sphere layer bounding the porous medium are reported and their dependence on the Reynolds number illustrated. It is shown that, at finite Reynolds numbers, a lift force acts on the spheres, which may be expected to contribute to the mobilization of bottom sediments. The results for the slip velocity at the surface of the porous layers are compared with the phenomenological Beavers–Joseph model. It is found that the values of the slip coefficient for pressure-driven and shear-driven flow are somewhat different, and also depend on the Reynolds number. A modification of the relation is suggested to deal with these features. The Appendix provides an alternative derivation of this modified relation.

Reynolds Number Effects on the Calibration of a Subminiature Four Hole Three Dimensional Wake Probe

2014 ◽  
Author(s):  
Gajanan Tatpatti ◽  
Sitaram Nekkanti
Keyword(s):  
Reynolds Number ◽  
Practical Importance ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Reynolds Number Effects ◽  
Number Variation ◽  
Yaw Angle ◽  
Nominal Dimension ◽  
Calibration Coefficients

A subminiature four-hole probe is designed and fabricated to be used specifically to measure wakes that occur in turbomachinery and its components. The probe has a nominal measuring area of 0.413 mm2 and has a nominal dimension of 0.254 mm in the direction across the wake downstream the trailing edge of a blade thus minimizing spatial and flow gradient errors in this direction. The non-nulling calibration of the probe is carried out in the pitch and yaw angle range of ±30° at 5° interval. The probe is calibrated at four different velocities, viz., 10 m/s, 20 m/s, 30 m/s and 50 m/s corresponding to the probe thickness Reynolds numbers in the range of 159 to 794 with objective of finding the effect of Reynolds number on the calibration coefficients. In addition to these, for practical importance the actual changes in yaw angle, pitch angle, static pressure, total pressure and velocity magnitude due to Reynolds number variation has been investigated. A method to incorporate the effect of Reynolds number for minimum interpolation errors is described.

Three-dimensional flow over two spheres placed side by side

1993 ◽  
Vol 246 ◽  
pp. 465-488 ◽  
Author(s):  
Inchul Kim ◽  
Said Elghobashi ◽  
William A. Sirignano
Keyword(s):  
Reynolds Number ◽  
Vortical Structure ◽  
Three Dimensional ◽  
Numerical Data ◽  
Reynolds Numbers ◽  
Near Wake ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Confined Flow ◽  
Small Spacing

Three-dimensional flow over two identical (solid or liquid) spheres which are held fixed relative to each other with the line connecting their centres normal to a uniform I stream is investigated numerically at Reynolds numbers 50, 100, and 150. We consider the lift, moment, and drag coefficients on the spheres and investigate their dependence on the distance between the two spheres. The computations show that, for a given Reynolds number, the two spheres are repelled when the spacing is of the order of the diameter but are weakly attracted at intermediate separation distances. For small spacing, the vortical structure of the near wake is significantly different from that of the axisymmetric wake that establishes at large separations. The partially confined flow passing between the two spheres entrains the flows coming around their other sides. Our results agree with available experimental and numerical data.

An Investigation of Factors Influencing the Calibration of Five-Hole Probes for Three-Dimensional Flow Measurements

1993 ◽  
Vol 115 (3) ◽  
pp. 513-519 ◽  
Author(s):  
R. G. Dominy ◽  
H. P. Hodson
Keyword(s):  
Reynolds Number ◽  
Large Scale ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Flow Measurements ◽  
Low Reynolds Numbers ◽  
Additional Information ◽  
Reynolds Number Effects ◽  
Low Speed Wind Tunnel ◽  
Probe Head

The effects of Reynolds number, Mach number, and turbulence on the calibrations of commonly used types of five-hole probe are discussed. The majority of the probes were calibrated at the exit from a transonic nozzle over a range of Reynolds numbers (7 × 103 < Re < 80 × 103 based on probe tip diameter) at subsonic and transonic Mach numbers. Additional information relating to the flow structure were obtained from a large-scale, low-speed wind tunnel. The results confirmed the existence of two distinct Reynolds number effects. Flow separation around the probe head affects the calibrations at relatively low Reynolds numbers while changes in the detailed structure of the flow around the sensing holes affects the calibrations even when the probe is nulled. Compressibility is shown to have little influence upon the general behavior of these probes in terms of Reynolds number sensitivity but turbulence can affect the reliability of probe calibrations at typical test Reynolds numbers.

Effect of Viscosity and Reynolds Number for Flow in Converging Microchannels

2011 ◽  
Author(s):  
Nelson Macken ◽  
Christopher Boutelle ◽  
Logan Osgood-Jacobs
Keyword(s):  
Reynolds Number ◽  
Cross Sections ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Interface Surface ◽  
Interface Location ◽  
Reynolds Number Effects ◽  
Flow Curvature ◽  
Microfluidic Flows ◽  
Flow Inertia

The interface between intersecting microfluidic flows is investigated experimentally. Two microchannel configurations are studied. Each configuration has a main channel and an intersecting daughter channel. The channel cross sections are equal and square with the intersection either at 90 or 45 degrees. Flow visualization is achieved using confocal fluorescence microscopy. The flow interface is examined for equal and unequal viscosities and a range of Reynolds numbers. Viscosity differences and Reynolds numbers influence the three-dimensional nature of the interface. As the Reynolds number increases, the increased flow inertia produces curvature in the interface surface perpendicular to the flow. Curvature is also evident in flows with unequal viscosities. The interface location at fixed flow ratios is independent of the Reynolds number, but varies significantly with unequal viscosity ratios. Viscosity and Reynolds number effects are similar in both the 45 and 90 degree configurations.

Onset of Transition in the Flow Over a Three-Dimensional Array of Rectangular Obstacles

1992 ◽  
Vol 114 (2) ◽  
pp. 251-255 ◽  
Author(s):  
S. V. Garimella ◽  
P. A. Eibeck
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Water Channel ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Channel Height ◽  
Circuit Boards ◽  
Three Dimensional Flow ◽  
Transfer Data ◽  
Array Geometry

Onset of transition is investigated in the flow over an array of protruding elements mounted on the bottom wall of a rectangular water channel simulating flow passages between adjacent circuit boards in computers. The element dimensions are held constant while the channel height and the element spacing are varied. Flow visualization and turbulence measurements are used to determine transition Reynolds numbers, which compare well with previous results obtained from heat transfer data. The complicated, three-dimensional flow field causes transition to be a function not only of flow rate and array geometry but also of location in the array. Transition occurs in the fully developed region of the array at a channel height-based Reynolds number of 700 for a channel height of 1.2 element heights, increasing to 1900 for a channel height of 3.6 element heights. However, when Reynolds number is defined based on element height, transition occurs at the same Reynolds number of 550 for all channel heights. Increasing the stream wise spacing between elements causes transition to occur at lower Reynolds numbers.

scholarly journals The Effect of the Reynolds Number on the Three-Dimensional Flow in a Straight Compressor Cascade

1988 ◽  
Author(s):  
Václav Cyrus
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Compressor Cascade ◽  
Simple Correlation ◽  
Three Dimensional Flow ◽  
Flow Angle ◽  
Low Reynolds Numbers ◽  
Dimensional Flow

A straight compressor cascade of aspect ratio 2 was tested in a low speed tunnel within Reynolds number Re1 = 45 000 – 150 000 and inlet flow angle α1 = 35° – 48°. The profile of the blade was NACA 65-12-10. The purpose of the paper was to obtain data on three–dimensional flow in a straight cascade at low Reynolds numbers. Some experimental results on secondary flow have been made into simple correlation relations.

Bifurcation Characteristics of Flows in Rectangular Sudden Expansion Channels

2005 ◽  
Author(s):  
Francine Battaglia ◽  
George Papadopoulos
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Critical Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Expansion Ratio ◽  
Sudden Expansion ◽  
Two Dimensional ◽  
Effective Expansion ◽  
Three Dimensional Simulations

The effect of three-dimensionality on low Reynolds number flows past a symmetric sudden expansion in a channel was investigated. The geometric expansion ratio of in the current study was 2:1 and the aspect ratio was 6:1. Both experimental velocity measurements and two- and three-dimensional simulations for the flow along the centerplane of the rectangular duct are presented for Reynolds numbers in the range of 150 to 600. Comparison of the two-dimensional simulations with the experiments revealed that the simulations fail to capture completely the total expansion effect on the flow, which couples both geometric and hydrodynamic effects. To properly do so requires the definition of an effective expansion ratio, which is the ratio of the downstream and upstream hydraulic diameters and is therefore a function of both the expansion and aspect ratios. When the two-dimensional geometry was consistent with the effective expansion ratio, the new results agreed well with the three-dimensional simulations and the experiments. Furthermore, in the range of Reynolds numbers investigated, the laminar flow through the expansion underwent a symmetry-breaking bifurcation. The critical Reynolds number evaluated from the experiments and the simulations was compared to other values reported in the literature. Overall, side-wall proximity was found to enhance flow stability, helping to sustain laminar flow symmetry to higher Reynolds numbers in comparison to nominally two-dimensional double-expansion geometries. Lastly, and most importantly, when the logarithm of the critical Reynolds number from all these studies was plotted against the reciprocal of the effective expansion ratio, a linear trend emerged that uniquely captured the bifurcation dynamics of all symmetric double-sided planar expansions.

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