Similarity in the turbulent near wake of bluff bodies

AIAA Journal ◽  
1975 ◽  
Vol 13 (11) ◽  
pp. 1425-1429 ◽  
Author(s):  
R. K. Sullerey ◽  
A. K. Gupta ◽  
C. S. Moorthy
Keyword(s):  
Bluff Bodies ◽  
Near Wake

Numerical Investigation of Flow Around Bluff Bodies

1998 ◽  
Vol 14 (3) ◽  
pp. 153-159 ◽  
Author(s):  
Chou-Jiu Tsai ◽  
Ger-Jyh Chen
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Bluff Bodies ◽  
Near Wake ◽  
Navier Stokes Equations ◽  
Physical Description ◽  
Geometrical Shapes ◽  
Flow Phenomena ◽  
Volume Method

ABSTRACTIn this study, fluid flow around bluff bodies are studied to examine the vortex shedding phenomenon in conjuction with the geometrical shapes of these vortex shedders. These flow phenomena are numerically simulated. A finite volume method is employed to solve the incompressible two-dimensional Navier-Stokes equations. Thus, quantitative descriptions of the vortex shedding phenomenon in the near wake were made, which lead to a detailed description of the vortex shedding mechanism. Streamline contours, figures of lift coefficent, and figures of drag coefficent in various time, are presented, respectively, for a physical description.

Flow Over Two Circular Disks in Tandem

1980 ◽  
Vol 102 (1) ◽  
pp. 104-111 ◽  
Author(s):  
T. Morel ◽  
M. Bohn
Keyword(s):  
Drag Reduction ◽  
Steady Flow ◽  
Unsteady Flows ◽  
Flow Regimes ◽  
Diameter Ratio ◽  
Bluff Bodies ◽  
Steady Flows ◽  
Near Wake ◽  
Total Drag ◽  
Circular Disks

Placing two or more bluff-bodies in tandem is known to lead, in some cases, to configurations with relatively low overall drag. The present study concerns one particular case where two disks of unequal diameters, normal to the flow, are placed in tandem for the purpose of drag reduction. It shows that very significant drag reductions may be achieved by proper sizing of the disk diameters and of the gap between them. Placing a properly sized disk at an optimum distance ahead of a single reference disk can result in a configuration whose total drag is up to 81 percent lower than that of the reference disk alone. If the additional disk is placed behind into the near-wake of the reference disk, the drag of the two-disk configuration can be up to 70 percent lower than for the reference disk alone. Four different flow regimes have been identified, depending on the diameter ratio of the two disks, two with relatively steady flows and two with unsteady flows. The absolute drag minimum was found to occur in one of the two steady-flow regimes.

Boundary-layer influences on the subsonic near-wake of bluff bodies

1994 ◽  
Vol 31 (2) ◽  
pp. 443-444 ◽  
Author(s):  
Colin P. Britcher ◽  
Charles W. Alcorn
Keyword(s):  
Boundary Layer ◽  
Bluff Bodies ◽  
Near Wake

Near-wake characteristics of various V-shaped bluff bodies

1994 ◽  
Vol 10 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Jing-Tang Yang ◽  
Go-Long Tsai ◽  
Wen-Bin Wang
Keyword(s):  
Bluff Bodies ◽  
Near Wake ◽  
Wake Characteristics

Comment on the Loss of Vorticity in the Near Wake of Bluff Bodies

1989 ◽  
Vol 111 (1) ◽  
pp. 104-105 ◽  
Author(s):  
M. M. Zdravkovich
Keyword(s):  
Three Dimensional ◽  
Nonlinear Effects ◽  
Bluff Bodies ◽  
Near Wake ◽  
Vortex Filaments ◽  
Loss Calculation ◽  
Apparent Loss

Fage and his co-workers [1,2] made a remarkable discovery in the 20’s that only half of the vorticity generated by bluff bodies remained concentrated in shed vortices. This belated comment reconsiders Fage’s method of “loss” calculation by examining nonlinear effects. The ignored effect of three dimensional distortion of vortex filaments before roll up might be another important cause for the “apparent” loss of vorticity.

A note on bluff body vortex formation

1995 ◽  
Vol 284 ◽  
pp. 217-224 ◽  
Author(s):  
Owen M. Griffin
Keyword(s):  
Bluff Body ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Initial Position ◽  
Bluff Bodies ◽  
Near Wake ◽  
Formation Region ◽  
Low Reynolds Numbers ◽  
Region Length ◽  
Low Reynolds

Green & Gerrard (1993) have presented in a recent paper the results of experiments to measure the distribution of vorticity in the near wake of a circular cylinder at low Reynolds numbers (up to Re = 220). They also compared the various definitions of the vortex formation region length which have been proposed by Gerrard (1966), Griffin (1974), and others for both high and low Reynolds numbers. The purpose of this note is to expand the work of Green & Gerrard, and to further their proposition that the end of the vortex formation region at all Reynolds numbers mark both the initial position of the fully shed vortex and the location at which its strength is a maximum. The agreement discussed here between several definitions for the formation region length will allow further understanding to be gained from investigations of the vortex wakes of stationary bluff bodies, and the wakes of oscillating bodies as well.

The wakes of cylindrical bluff bodies at low Reynolds number

1978 ◽  
Vol 288 (1354) ◽  
pp. 351-382 ◽  
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
The Body ◽  
Circular Cylinders ◽  
Bluff Bodies ◽  
Near Wake ◽  
Cross Sectional ◽  
Molecular Diffusivity ◽  
Splitter Plates ◽  
Low Reynolds

Experiments on the near wake of a cylinder will be discribed in an attempt to present a coherent picture of the events encountered as the Reynolds number increases from small values up to values of a few thousand. Much work on this subject has already been done, but there are gaps in our description of these flows as well as more fundamental deficiencies in our understanding of them. The subject has been reviewed several times and most recently by Berger & Wille (1972) whose paper covers much of the ground that will be discussed again here. The present work may be regarded as built upon this latest review. I remember with gratitude many helpful discussions with the late Rudolph Wille who contributed so much to this subject. The investigation has concentrated on circular cylinders, but the wakes of bluff cylinders of different cross sectional shapes have also been observed. Bluff cylinders in general are considered in §§4 and 5, together with the effect of splitter plates on circular cylinders in §9. The experiments concern, almost exclusively, flow visualization of the wakes by means of dye washed from the bodies. The patterns of dye observed are, therefore, filament line representations of the flow leaving the separation lines on the body. It must be stressed that the dye does not make visible the vorticity bearing fluid because at low Reynolds number, vorticity diffuses considerably more rapidly than does dye. The ratio of the molecular diffusivity of momentum to that of mass of dye is of the order of 100.

Analysis of the Near Wake of Bluff Bodies in Ground Proximity

2002 ◽  
Author(s):  
Szabolcs R. Balkanyi ◽  
Luis P. Bernal ◽  
Bahram Khalighi
Keyword(s):  
Vector Fields ◽  
Aerodynamic Drag ◽  
Base Pressure ◽  
Wake Flow ◽  
Vehicle Body ◽  
Recirculation Region ◽  
Bluff Bodies ◽  
Pressure Measurements ◽  
Near Wake ◽  
Mean Velocity

The effect of several drag reducing devices on the near wake of a generic ground vehicle body was investigated. Drag and base pressure measurements were conducted to identify the effects of the devices on the base drag. A Particle Image Velocimetry (PIV) study was conducted to determine changes of the near wake flow field. Averages of more than 200 PIV velocity vector fields were used to compute the mean velocity and turbulent stresses at several cross section planes. The results of the drag and base pressure measurements show that significant reductions of the total aerodynamic drag (as high as 48%) can be achieved with relatively simple devices. The results also indicated that models with base cavity have lower drag than their counter parts without it. The base pressure distributions showed a strong effect of the ground, resulting in decrease of pressure towards the lower half of the base. The PIV study showed that the extent of the recirculation region is not strongly affected by the drag reducing devices. The tested devices however, were found to have a strong effect on the underbody flow. A rapid upward deflection of the underbody flow in the near wake was observed. The devices were also found to reduce the turbulent stresses in the near wake. The turbulent stresses were found to decrease in magnitude with increasing drag reduction.

Transport in the near aerodynamic wakes of flat plates

1982 ◽  
Vol 120 ◽  
pp. 185-197 ◽  
Author(s):  
A. S. M. Maclennan ◽  
J. H. Vincent
Keyword(s):  
Free Stream ◽  
Bluff Bodies ◽  
Wake Region ◽  
Small Particles ◽  
Flat Plates ◽  
Main Attention ◽  
Near Wake ◽  
Free Stream Turbulence ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

An experimental investigation has been carried out into the nature of the transport of airborne material in the near aerodynamic wakes of bluff bodies with simple shapes. The main attention was focused on the essential differences existing between axi- symmetric flows (as about disks) and two-dimensional flows (as about rectangular long thin flat plates). Measurements were made for such bodies of the near-wake residence time of injected small particles, along with other and more familiar near- wake properties such as the vortex-shedding frequency and base pressure. It was concluded for disks that the transport of material into and out of the near-wake region is dominated by turbulent diffusion, and is strongly influenced by free-stream turbulence, especially for free-stream turbulence whose length scale is substantially smaller than the disk diameter. For rectangular flat plates, transport is dominated by the periodic shedding of vortices, and to only a secondary extent by turbulent motions, and is not strongly influenced by free-stream turbulence.

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