Wake-Shear Layer Interaction and the Onset of Turbulence Behind a Circular Cylinder

1987 ◽  
pp. 82-97
Author(s):  
A. Kourta ◽  
H. C. Boisson ◽  
M. Braza ◽  
P. Chassaing ◽  
H. Ha Minh
Keyword(s):  
Circular Cylinder ◽  
Shear Layer ◽  
Layer Interaction ◽  
Onset Of Turbulence

Aero-Thermodynamic Loss Analysis in Cases of Normal Shock Wave-Turbulent Shear Layer Interaction

1997 ◽  
Vol 119 (2) ◽  
pp. 297-303 ◽  
Author(s):  
J. K. Kaldellis
Keyword(s):  
Shear Layer ◽  
Practical Interest ◽  
Flow Simulation ◽  
Strong Shock ◽  
Turbulent Shear ◽  
Complex Flow ◽  
Loss Model ◽  
Layer Interaction ◽  
Loss Analysis ◽  
Shock Loss

Transonic-supersonic decelerating flow cases appearing in modern turbomachines are some of the most complex flow cases in fluid mechanics which also present practical interest. In the present work, a closed and coherent shock loss model is proposed based on the complete viscous flow simulation using some fast and reliable computational tools. The resulting model describes accurately the entropy rise and the total pressure loss in cases of strong shock-shear layer interaction and cancels the need to use low speed correlations modified for compressibility effects and extrapolated to transonic-supersonic flow cases. The accuracy and the reliability of the proposed shock-loss model are verified using detailed experimental data concerning various flow cases which present either flow separation or industrial interest.

scholarly journals Unsteady Flows in the Vortex Region Behind a Circular Cylinder Started Impulsively : 1st Report, Feeding Mechanism of Vorticity and Onset of Turbulence

1985 ◽  
Vol 28 (245) ◽  
pp. 2599-2607 ◽  
Author(s):  
Hiroshi NAGATA ◽  
Hideaki FUNADA ◽  
Kenji KAWAI ◽  
Tatsuya MATSUI
Keyword(s):  
Circular Cylinder ◽  
Unsteady Flows ◽  
Feeding Mechanism ◽  
Onset Of Turbulence

Sting-free measurements on a magnetically supported right circular cylinder aligned with the free stream

2008 ◽  
Vol 596 ◽  
pp. 49-72 ◽  
Author(s):  
HIROSHI HIGUCHI ◽  
HIDEO SAWADA ◽  
HIROYUKI KATO
Keyword(s):  
Circular Cylinder ◽  
Shear Layer ◽  
Free Stream ◽  
Aerodynamic Force ◽  
Cross Flow ◽  
Leading Edge ◽  
Magnetic Suspension ◽  
Recirculation Region ◽  
Mean Velocity ◽  
Wide Range

The flow over cylinders of varying fineness ratio (length to diameter) aligned with the free stream was examined using a magnetic suspension and balance system in order to avoid model support interference. The drag coefficient variation of a right circular cylinder was obtained for a wide range of fineness ratios. Particle image velocimetry (PIV) was used to examine the flow field, particularly the behaviour of the leading-edge separation shear layer and its effect on the wake. Reynolds numbers based on the cylinder diameter ranged from 5×104 to 1.1×105, while the major portion of the experiment was conducted at ReD=1.0×105. For moderately large fineness ratio, the shear layer reattaches with subsequent growth of the boundary layer, whereas over shorter cylinders, the shear layer remains detached. Differences in the wake recirculation region and the immediate wake patterns are clarified in terms of both the mean velocity and turbulent flow fields, including longitudinal vortical structures in the cross-flow plane of the wake. The minimum drag corresponded to the fineness ratio for which the separated shear layer reattached at the trailing edge of the cylinder. The base pressure was obtained with a telemetry technique. Pressure fields and aerodynamic force fluctuations are also discussed.

Radiated Sound from a Circular Cylinder in a Turbulent Shear Layer

2014 ◽  
Vol 13 (7-8) ◽  
pp. 511-532 ◽  
Author(s):  
Michael J. Bilka ◽  
Peter Kerrian ◽  
Mark H. Ross ◽  
Scott C. Morris
Keyword(s):  
Circular Cylinder ◽  
Shear Layer ◽  
Turbulent Shear ◽  
Turbulent Shear Layer ◽  
Radiated Sound

Mitigating Blockage Effects on Flow Over a Circular Cylinder in an Adaptive-Wall Wind Tunnel

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Michael Bishop ◽  
Serhiy Yarusevych
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Shear Layer ◽  
Cylinder Surface ◽  
Blockage Ratio ◽  
Shear Layer Instability ◽  
Frequency Increase ◽  
Pressure Distributions ◽  
Instability Frequency

The effect of wall streamlining on flow development over a circular cylinder was investigated experimentally in an adaptive-wall wind tunnel. Experiments were carried out for a Reynolds number of 57,000 and three blockage ratios of 5%, 8%, and 17%. Three test section wall configurations were investigated, namely, geometrically straight walls (GSW), aerodynamically straight walls (ASW), and streamlined walls (SLW). The results show that solid blockage effects are evident in cylinder surface pressure distributions for the GSW and ASW configurations, manifested by an increased peak suction and base suction. Upon streamlining the walls, pressure distributions for each blockage ratio investigated closely match distributions expected for low blockage ratios. Wake blockage limits wake growth in the GSW configuration at 7.75 and 15 diameters downstream of the cylinder for blockages of 17% and 8%, respectively. This adverse effect can be rectified by streamlining the walls, with the resulting wake width development matching that expected for low blockage ratios. Wake vortex shedding frequency and shear layer instability frequency increase in the GSW and ASW configurations with increasing blockage ratio. The observed invariance of the near wake width with wall configuration suggests that the frequency increase is caused by the increased velocity due to solid blockage effects. For all the blockage ratios investigated, this increase is rectified in the SLW configuration, with the resulting Strouhal numbers of about 0.19 matching that expected for low blockage ratios at the corresponding Reynolds number. Blockage effects on the shear layer instability frequency are also successfully mitigated by streamlining the walls.

LES Analysis of Turbulence Effects on Unsteady Flows Past a Circular Cylinder

2003 ◽  
Author(s):  
Tetsuro Tamura ◽  
Yoshiyuki Ono ◽  
Kohji Hashida
Keyword(s):  
Circular Cylinder ◽  
Shear Layer ◽  
Bluff Body ◽  
Unsteady Flows ◽  
Aerodynamic Characteristics ◽  
Cylinder Wake ◽  
Eddy Simulation ◽  
Inflow Boundary Condition ◽  
Large Eddy ◽  
Turbulence Effects

Recent advancement of LES (Large Eddy Simulation) technique for turbulent wake has made it possible to numerically investigate the turbulence effects on aerodynamic characteristics of a bluff body. Here we carry out LES of wake flows past a circular cylinder in the subcritical Reynolds number regime. For inflow boundary condition, homogeneous turbulence generated statistically is given time-sequentially. We bring into focus the interaction between the oncoming turbulence and the shear layer separated from a circular cylinder. Shear layer instability easily occurs under such a stimulation and details of its behavior are visualized. Turbulence effects on unsteady flows in the cylinder wake are discussed. The resulting aerodynamic characteristics and their physical mechanism are clarified.

Effect of Shear Layer Interaction on Acoustic Response of Coaxial Side Branch Resonators

2007 ◽  
Author(s):  
P. Oshkai ◽  
A. Velikorodny ◽  
T. Yan
Keyword(s):  
Shear Layer ◽  
Acoustic Waves ◽  
Acoustic Power ◽  
Shear Layers ◽  
Side Branch ◽  
Acoustic Response ◽  
Quality Factors ◽  
Hydrodynamic Modes ◽  
Layer Interaction ◽  
Turbulent Inflow

Fully turbulent inflow past a coaxial side branch resonator mounted in a duct can give rise to pronounced flow oscillations due to coupling between separated shear layers and standing acoustic waves. Experimental investigation of acoustically-coupled shear layers is conducted using digital particle image velocimetry in conjunction with unsteady pressure measurements. Global instantaneous flow images, as well as phase-averaged images, are evaluated to provide insight into the flow physics during tone generation. The emphasis is on the effect of shear layer interaction on the acoustic response of the resonator during the first and second hydrodynamic modes of the shear layer oscillation. Onset of the locked-on resonant states is characterized in terms of the acoustic pressure amplitudes and the quality factors of the corresponding spectral peaks. Moreover, patterns of generated acoustic power are calculated using a semi-empirical approach. As the level of interaction between the separated shear layers is increased, spatial structure of the acoustic source undergoes a substantial transformation.

On vortex formation from a cylinder. Part 1. The initial instability

1988 ◽  
Vol 190 ◽  
pp. 491-512 ◽  
Author(s):  
M. F. Unal ◽  
D. Rockwell
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Circular Cylinder ◽  
Shear Layer ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Absolute Instability ◽  
Near Wake ◽  
Lower Range ◽  
Fluctuation Amplitude

Vortex shedding from a circular cylinder is examined over a tenfold range of Reynolds number, 440 ≤ Re ≤ 5040. The shear layer separating from the cylinder shows, to varying degrees, an exponential variation of fluctuating kinetic energy with distance downstream of the cylinder. The characteristics of this unsteady shear layer are interpreted within the context of an absolute instability of the near wake. At the trailing-end of the cylinder, the fluctuation amplitude of the instability correlates well with previously measured values of mean base pressure. Moreover, this amplitude follows the visualized vortex formation length as Reynolds number varies. There is a drastic decrease in this near-wake fluctuation amplitude in the lower range of Reynolds number and a rapid increase at higher Reynolds number. These trends are addressed relative to the present, as well as previous, observations.

Mitigating Blockage Effects on Flow Over a Circular Cylinder in an Adaptive-Wall Wind Tunnel

2010 ◽  
Author(s):  
Michael Bishop ◽  
Serhiy Yarusevych
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Circular Cylinder ◽  
Shear Layer ◽  
Cylinder Surface ◽  
Blockage Ratio ◽  
Shear Layer Instability ◽  
Frequency Increase ◽  
Pressure Distributions ◽  
Instability Frequency

The effect of wall streamlining on flow development over a circular cylinder was investigated experimentally in an adaptive-wall wind tunnel. Experiments were carried out for a Reynolds number of 57,000 and three blockage ratios of 5%, 8%, and 17%. Three test section wall configurations were investigated, namely, geometrically straight walls (GSW), aerodynamically straight walls (ASW), and streamlined walls (SLW). The results show that solid blockage effects are clearly evident in cylinder surface pressure distributions for the GSW and ASW configurations, manifested by an increased peak suction and base suction. Upon streamlining the walls, pressure distributions for each blockage ratio investigated closely match distributions expected for low blockage ratios. Wake blockage limits wake growth in the GSW configuration at 7.75 and 15 diameters downstream of the cylinder for blockages of 17% and 8%, respectively. This adverse effect can be rectified by streamlining the walls, with the resulting wake width development matching that expected for low blockage ratios. Wake vortex shedding frequency and shear layer instability frequency increase in the GSW and ASW configurations with increasing blockage ratio. The observed invariance of the near wake width with wall configuration suggests that the frequency increase is caused by the increased velocity due to solid blockage effects. For all the blockage ratios investigated, this increase is rectified in the SLW configuration, with the resulting Strouhal numbers of about 0.19 matching that expected for low blockage ratios at the corresponding Reynolds number. Blockage effects on the shear layer instability frequency are also successfully mitigated by streamlining the walls.

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