An experimental study of steady and pulsating cross-flow over a semi-staggered tube bundle

This paper describes an experimental study of the cross-flow characteristics in a semi-staggered tube bundle for Reynolds numbers in the range 1100-12 900. It is shown that by displacing transversely the tubes in the even rows of an in-line bundle by one diameter the vortex-shedding mechanism is suppressed. Vortex shedding is re-established and reinforced by pulsations superimposed on to the approaching flow and a considerable increase in the power of the associated velocity fluctuations is observed in the bundle. Two cases of pulsating flow are examined with different effects on the flow structure of the bundle. Detailed measurements of the mean and fluctuating velocity fields in the semi-staggered tube bundle together with flow visualization images are also reported in the paper in order to examine in depth the effects of tube displacement and flow pulsations. Comparisons with in-line and staggered configurations having the same spacing-to-diameter ratios are made.

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Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

Aerospace Science and Technology ◽

10.1016/j.ast.2020.106377 ◽

2021 ◽

Vol 108 ◽

pp. 106377

Author(s):

Mohammed Faheem ◽

Aqib Khan ◽

Rakesh Kumar ◽

Sher Afghan Khan ◽

Waqar Asrar ◽

...

Keyword(s):

Experimental Study ◽

Flow Characteristics ◽

Mean Flow ◽

The Mean

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Natural logarithms

Journal of Fluid Mechanics ◽

10.1017/jfm.2012.608 ◽

2013 ◽

Vol 718 ◽

pp. 1-4 ◽

Cited By ~ 2

Author(s):

B. J. McKeon

Keyword(s):

Turbulent Flows ◽

Reynolds Numbers ◽

Streamwise Velocity ◽

Wall Turbulence ◽

Significant Advance ◽

Mean Velocity ◽

Velocity Fluctuations ◽

Logarithmic Scaling ◽

The Mean ◽

High Reynolds

AbstractMarusic et al. (J. Fluid Mech., vol. 716, 2013, R3) show the first clear evidence of universal logarithmic scaling emerging naturally (and simultaneously) in the mean velocity and the intensity of the streamwise velocity fluctuations about that mean in canonical turbulent flows near walls. These observations represent a significant advance in understanding of the behaviour of wall turbulence at high Reynolds number, but perhaps the most exciting implication of the experimental results lies in the agreement with the predictions of such scaling from a model introduced by Townsend (J. Fluid Mech., vol. 11, 1961, pp. 97–120), commonly termed the attached eddy hypothesis. The elegantly simple, yet powerful, study by Marusic et al. should spark further investigation of the behaviour of all fluctuating velocity components at high Reynolds numbers and the outstanding predictions of the attached eddy hypothesis.

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LDV and PIV Velocity Results in a Thermosiphon

Volume 2: Symposia, Parts A, B, and C ◽

10.1115/fedsm2003-45601 ◽

2003 ◽

Author(s):

J. Kulman ◽

D. Gray ◽

S. Sivanagere ◽

S. Guffey

Keyword(s):

Large Scale ◽

Single Phase ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Flow Patterns ◽

Laser Doppler Velocimeter ◽

Mean Velocity ◽

Developed Turbulence ◽

The Mean ◽

Good Agreement

Heat transfer and flow characteristics have been determined for a single-phase rectangular loop thermosiphon. The plane of the loop was vertical, and tests were performed with in-plane tilt angles ranging from 3.6° CW to 4.2° CCW. Velocity profiles were measured in one vertical leg of the loop using both a single-component Laser Doppler Velocimeter (LDV), and a commercial Particle Image Velocimeter (PIV) system. The LDV data and PIV data were found to be in good agreement. The measured average velocities were approximately 2–2.5 cm/s at an average heating rate of 70 W, and were independent of tilt angle. Significant RMS fluctuations of 10–20% of the mean velocity were observed in the test section, in spite of the laminar or transitional Reynolds numbers (order of 700, based on the hydraulic diameter). These fluctuations have been attributed to vortex shedding from the upstream temperature probes and mitre bends, rather than to fully developed turbulence. Animations of the PIV data clearly show these large scale unsteady flow patterns. Multiple steady state flow patterns were not observed.

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A Continuous Prediction Method for Fully Developed Laminar, Transitional, and Turbulent Flows in Pipes

Journal of Applied Mechanics ◽

10.1115/1.3423552 ◽

1975 ◽

Vol 42 (1) ◽

pp. 51-54 ◽

Cited By ~ 2

Author(s):

N. W. Wilson ◽

R. S. Azad

Keyword(s):

Turbulent Flows ◽

Flow Characteristics ◽

Prediction Method ◽

Reynolds Numbers ◽

Mean Flow ◽

Number Range ◽

Circular Pipes ◽

The Mean ◽

Single Set ◽

Good Agreement

A single set of equations is developed to predict the mean flow characteristics in long circular pipes operating at laminar, transitional, and turbulent Reynolds numbers. Generally good agreement is obtained with available data in the Reynolds number range 100 < Re < 500,000.

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Vortex Shedding from Smooth and Roughened Cylinders in Cross-Flow near a Plane Surface

Aeronautical Quarterly ◽

10.1017/s0001925900008532 ◽

1979 ◽

Vol 30 (1) ◽

pp. 305-321 ◽

Cited By ~ 27

Author(s):

G. Buresti ◽

A. Lanciotti

Keyword(s):

Vortex Shedding ◽

Plane Surface ◽

Cross Flow ◽

Reynolds Numbers ◽

Cylinder Surface ◽

Hot Wire ◽

Cylinder Axis ◽

Supercritical Regime ◽

Subcritical Regime ◽

Smooth Cylinder

SummaryThe characteristics of the flow field around a circular cylinder in cross-flow placed at various distances from a plane, parallel both to the flow and to the cylinder axis, were analysed using a hot wire anemometer. Experiments were performed in a wind tunnel with Reynolds numbers ranging from 0.85×105 to 3×105. The spectra of the hot wire signals were obtained using a Fast Fourier Transform technique programmed on a PDP 11/40 computer. As regards a smooth cylinder, the main features of the vortex shedding mechanism in the subcritical regime remained unaltered for distances from the plane greater than approximately 0.4 diameters; in particular the Strouhal frequency did not show any significant variation relative to the typical value for an isolated cylinder. As for lower values of the distance from the plane, the regular vortex shedding disappeared and the hot wire spectra showed typical turbulent features. The possibility of obtaining supercritical conditions by roughening the cylinder surface was confirmed together with the importance of the Reynolds number based on the typical roughness size, Rk, in the evaluation of the flow regime around the cylinder. In the case of roughened cylinders, and with values of Rk below-350, the regular vortex shedding disappeared at a distance from the plane smaller than 0.3 diameters. This fact suggests that, at least in part of the supercritical regime, the influence of the plane can be smaller than in the subcritical regime.

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Fluctuating forces on a rigid circular cylinder in confined flow

Journal of Fluid Mechanics ◽

10.1017/s0022112076002607 ◽

1976 ◽

Vol 78 (3) ◽

pp. 561-576 ◽

Cited By ~ 89

Author(s):

A. Richter ◽

E. Naudascher

Keyword(s):

Circular Cylinder ◽

Vortex Shedding ◽

Reynolds Numbers ◽

Critical Value ◽

Experimental Information ◽

Rectangular Duct ◽

Wide Range ◽

Confined Flow ◽

The Mean ◽

Lift And Drag

The fluctuating lift and drag acting on a long, rigidly supported circular cylinder placed symmetrically in a narrow rectangular duct were investigated for various blockage percentages over a wide range of Reynolds numbers around the critical value. The data obtained permit a full assessment of the effect of confinement on the mean-drag coefficient, the root-mean-square values of both the drag and the lift fluctuations, the Strouhal number of the dominant vortex shedding, and the Reynolds number marking transition from laminar to turbulent flow separation. Besides experimental information on a subject on which little is known so far, the paper provides a basis for the deduction of better correction procedures concerning the effects of blockage.

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Three Dimensional Numerical Modelling of Staggered Tube Bundle Turbulent Crossflow in Duct

Heat Transfer: Volume 3 ◽

10.1115/ht2005-72532 ◽

2005 ◽

Author(s):

Ahad Ramezanpour ◽

Hassan Shirvani ◽

Ramin Rahmani ◽

Iraj Mirzaee

Keyword(s):

Nusselt Number ◽

Numerical Study ◽

Tube Bundle ◽

Three Dimensional ◽

Cross Flow ◽

Reynolds Numbers ◽

Wall Function ◽

Flat Plates ◽

Geometrical Characteristics ◽

Commercial Code

A numerical study has been conducted to investigate the three dimensional (3D) staggered tube bundle turbulent cross flow confined between two parallel flat plates using RNG k-ε model and standard wall function utilizing commercial code FLUENT. The maximum Reynolds numbers of 1000, 5000, and 50000 and the distance between plates of H = 3, 5, 10, 15, and 20 mm have been considered. The arrangement of the staggered tube bundle is fix with geometrical characteristics of Sn/D = 1.5 and Sp/D = 1.2 which has been found optimum in previous two-dimensional studies. The constant temperature of 360K on tubes, constant inlet flow and plates’ temperature of 300K have been set as the boundary conditions. The global Nusselt number, friction factor for the dissimilar Reynolds numbers, distance between plates, local Nusselt number and different angles on first and third tubes have been evaluated.

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Properties of the mean recirculation region in the wakes of two-dimensional bluff bodies

Journal of Fluid Mechanics ◽

10.1017/s0022112097007179 ◽

1997 ◽

Vol 351 ◽

pp. 167-199 ◽

Cited By ~ 83

Author(s):

S. BALACHANDAR ◽

R. MITTAL ◽

F. M. NAJJAR

Keyword(s):

Reynolds Number ◽

Shear Stress ◽

Reynolds Stress ◽

Vortex Shedding ◽

Reynolds Numbers ◽

Recirculation Region ◽

Bluff Bodies ◽

Two Dimensional ◽

Stress Components ◽

The Mean

The properties of the time- and span-averaged mean wake recirculation region are investigated in separated flows over several different two-dimensional bluff bodies. Ten different cases are considered and they divide into two groups: cylindrical geometries of circular, elliptic and square cross-sections and the normal plate. A wide Reynolds number range from 250 to 140000 is considered, but in all the cases the attached portion of the boundary layer remains laminar until separation. The lower Reynolds number data are from direct numerical simulations, while the data at the higher Reynolds number are obtained from large-eddy simulation and the experimental work of Cantwell & Coles (1983), Krothapalli (1996, personal communication), Leder (1991) and Lyn et al. (1995). Unlike supersonic and subsonic separations with a splitter plate in the wake, in all the cases considered here there is strong interaction between the shear layers resulting in Kármán vortex shedding. The impact of this fundamental difference on the distribution of Reynolds stress components and pressure in relation to the mean wake recirculation region (wake bubble) is considered. It is observed that in all cases the contribution from Reynolds normal stress to the force balance of the wake bubble is significant. In fact, in the cylinder geometries this contribution can outweigh the net force from the shear stress, so that the net pressure force tends to push the bubble away from the body. In contrast, in the case of normal plate, owing to the longer wake, the net contribution from shear stress outweighs that from the normal stress. At higher Reynolds numbers, separation of the Reynolds stress components into incoherent contributions provides more insight. The behaviour of the coherent contribution, arising from the dominant vortex shedding, is similar to that at lower Reynolds numbers. The incoherent contribution to Reynolds stress, arising from small-scale activity, is compared with that of a canonical free shear layer. Based on these observations a simple extension of the wake model (Sychev 1982; Roshko 1993a, b) is proposed.

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Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

Journal of Fluids Engineering ◽

10.1115/1.1358844 ◽

2000 ◽

Vol 123 (2) ◽

pp. 347-358 ◽

Cited By ~ 63

Author(s):

P. Bagchi ◽

M. Y. Ha ◽

S. Balachandar

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Vortex Shedding ◽

Axisymmetric Flow ◽

Three Dimensional ◽

Cross Flow ◽

Reynolds Numbers ◽

Temperature Fields ◽

Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

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