Investigation of flow characteristics around a sphere placed in a boundary layer over a flat plate

Özgören, Muammer; Okbaz, Abdülkerim; Doğan, Sercan; Şahi̇n, Beşi̇r; Akıllı, Hüseyin

doi:10.1016/j.expthermflusci.2012.05.014

Cited by 43 publications

(24 citation statements)

References 25 publications

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“…At the submerging elevation of h/D = 2.00, the free-surface effects are minimum and beyond h/D = 2.0, it may be assumed that these free-surface effects on the sphere wake structure disappear [1]. Ozgoren et al (2009Ozgoren et al ( , 2011aOzgoren et al ( and 2011b and (2012a and 2012b) investigated interaction between a sphere wake and free-surface in the range of 0≤h/D≤2.0 with different submerging ratios [2][3][4][5][6]. They found that free surface has strong effect in the three-dimensional wake of the sphere.…”

Section: Introductionmentioning

confidence: 99%

“…Under the uniform incoming flow condition, many of the studies to control the flow structure around a sphere were performed by Ozgoren et al Leweke et al (1999), Taneda (1978), Achenbach (1974), Wu and Faeth (1993) and further investigations cited therein [7][8][9][10][11][12][13][14][15][16][17][18]. Control of flow structure around a sphere for various active and passive methods was studied by Suryanarayana and Prabhu (2000), Suryanarayana and Meier (1995), Suryanarayana et al (1993), Ozgoren et al(2011bOzgoren et al( , 2011c, Kim and Durbin (1988), Kiya (1988), Owen and Bearman (1988), Mehta (1985) and further investigations cited therein [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

Özgören

Doğan

Okbaz

et al. 2013

EPJ Web of Conferences

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Abstract.Comparison of the experimental results of turbulent flow structures between a smooth sphere and a sphere with a vent hole, roughened, and o-ring is presented in the presence of a free-surface. Dye visualization and particle image velocimetry (PIV) techniques were performed to examine effects of passive control methods on the sphere wake for Reynolds number Re = 5000 based on the sphere diameter with a 42.5mm in an open water channel. Instantaneous and time-averaged flow patterns in the wake region of the sphere were examined from point of flow physics for the different sphere locations in the range of 0≤h/D ≤2.0 where h was the space between the top point of the sphere and the free surface. The ratio of ventilation hole to sphere diameter was 0.15, o-ring was located at 55 o with a 2 mm from front stagnation point of the sphere and roughened surface was formed by means of totally 410 circular holes with a 3 mm diameter and around 2 mm depth in an equilateral triangle arrangement. The flow characteristics of instantaneous velocity vectors, vorticity contours, time-averaged streamline patterns, Reynolds stress correlations and streamwise and cross-stream velocity fluctuations for both the smooth and passively controlled sphere were interpreted.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

Özgören

Doğan

Okbaz

et al. 2013

EPJ Web of Conferences

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“…When a spherical geometry located near to a flat surface such as a wall or ground, the interaction between developing velocity profile in the boundary layer of the flat surface and flow around the sphere cause vortex shedding characteristic to change dramatically. As an example to these changes, Ozgoren et al [16] stated that aforementioned interaction results in asymmetry in the strength of vortex shedding from upper and lower sides of the sphere and changes the direction of the mean force acting over the body away from the plane wall. Ozgoren et al [16] placed a sphere having 42.5mm diameter in a 63mm thick turbulent boundary layer for Re=5000 in order to investigate the wake flow of the sphere via a PIV system.…”

Section: Introductionmentioning

confidence: 99%

Wake structures of two side by side spheres in a tripped boundary layer flow

Canlı

Özgören

Doğan

et al. 2014

EPJ Web of Conferences

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Abstract. Two independent spheres were placed in a side by side arrangement and flow structure in the wake region of the spheres was investigated with a Particle Image Velocimetry (PIV) system when the spheres were in a boundary layer over a flat plate as a special case. Reynolds number was 5000 based on the sphere diameter which was 42.5 mm. Boundary layer was tripped 8mm away from the leading edge of the flat plate with a 5 mm trip wire. The thickness of the hydrodynamically developed boundary layer was determined as 63mm which was larger than the sphere diameter of D=42.5mm. Wake region of the spheres was examined from point of flow physics for the different sphere locations in the ranges of 0G/D 1.5 and 0S/D 1.5 where G and S were the distance between the spheres and the distance between the bottom point of the spheres and the flat plate surface, respectively. Depending on the different sphere locations, instantaneous and time averaged vorticity data, scalar values of time-averaged velocity components and their root mean square (rms) values and time averaged vorticity data are presented in the study for the evaluation of wake region of the spheres. It is demonstrated that the gap between the two spheres and the interaction between the gap and the boundary layer greatly affects flow pattern, especially when spheres are located near to the flat plate surface, i.e. S/D=0.1 for 0G/D 1.5. Different distances between the spheres resulted in various flow patterns as the spheres were approached to the flat plate. The distance S/D=0.1 for all gap values has the strongest effect on the wake structures. Beyond G/D=1.0, the sphere wakes tend to be similar to single sphere case. The instantaneous vorticity fields of the side by side arrangements comprised wavy structures in higher level comparing to an individual sphere case. The gap flow intensifies the occurrence of small scale eddies in the wake region. The submersion rate of the spheres actually determines the characteristics of the wake region and is affected from boundary layer flow in a gradually decreasing manner.

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“…It was observed that a continuous flow development involving shearing phenomena and the interactions of shedding vortices caused a high rate of fluctuations over the whole flow field, although most of the time-averaged flow patterns were almost symmetric about the two downstream spheres [9,10]. Similarly, Tyagi et al [11] studied the effect of free-stream turbulence on the sphere wake and they found that the vortex shedding process downstream of the sphere was reduced when large organized motions were suppressed by the free-stream turbulence.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer Characteristics of Nanofuid Flow around an Elliptical Cylinder

Zerradi¹,

Mizani²,

Dezairi³

et al. 2016

Int J Adv Tech

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This paper presents the results of extensive numerical simulations, based on the control volume method, of 2D nanofluid fluid flow around a heated elliptical cylinder with different incidence angle and aspect ratio. The continuity and momentum equations have been numerically solved using a SIMPLE algorithm. Two types of nanofluids consisting of Al 2 O 3 and CuO nanoparticles dispersed separately in base fluids of water and ethylene glycol mixture 60:40 (by mass), were selected to evaluate their effect on the flow over elliptical cylinder, also their superiority over conventional fluids. The thermo-physical parameters of nanofluid have been estimated using the theory of one fluid phase, a contemporary correlations of thermal conductivity and viscosity of nanofluids have been used in this paper, which are functions of particle volumetric concentration as well as temperature. The results of heat transfer characteristics of nanofluid flow over elliptical cylinder reveled clear improvement comparing with the base fluids. This enhancement is more important in flows with different geometry characteristics of the elliptical cylinder. While the aspect ratio and the incidence angle, exert significant influence on the heat transfer characteristics. The obtained results indicate that the use of aspect ratio 0.83 and incidence angle 79.2° lead to the highest amounts of heat transfer inside the tube.

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Investigation of flow characteristics around a sphere placed in a boundary layer over a flat plate

Cited by 43 publications

References 25 publications

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

Wake structures of two side by side spheres in a tripped boundary layer flow

Heat Transfer Characteristics of Nanofuid Flow around an Elliptical Cylinder

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