Sound generation by a two-dimensional circular cylinder in a uniform flow

2002 ◽  
Vol 471 ◽  
pp. 285-314 ◽  
Author(s):  
OSAMU INOUE ◽  
NOZOMU HATAKEYAMA
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Doppler Effect ◽  
Sound Pressure ◽  
Pressure Pulse ◽  
Positive Pressure ◽  
Pressure Waves ◽  
Two Dimensional ◽  
The Doppler Effect ◽  
Mach Numbers

The sound generated by a circular cylinder in a flow at low Mach numbers is investigated by direct solution of the two-dimensional unsteady compressible Navier–Stokes equations. Results show that sound pressure waves are generated primarily by vortex shedding from the cylinder surface into its wake. When a vortex is shed from one side of the cylinder, a negative pressure pulse is generated from that side whereas a positive pressure pulse is generated from the other side; alternate vortex shedding from the upper and lower sides of the cylinder produces negative and positive pulses alternately and thus produces sound pressure waves on both sides. The dipolar nature of the generated sound is confirmed; lift dipole dominates the sound field. The Doppler effect is shown to play an important role at finite Mach numbers. The direct solutions are also compared with the solutions obtained by Curle's acoustic analogy. The results show that Curle's solution describes well not only the generation mechanism of the sound but also the propagation process if we take the Doppler effect into consideration.

The vortex-shedding process behind two-dimensional bluff bodies

1982 ◽  
Vol 116 ◽  
pp. 77-90 ◽  
Author(s):  
A. E. Perry ◽  
M. S. Chong ◽  
T. T. Lim
Keyword(s):  
Circular Cylinder ◽  
Flow Visualization ◽  
Vortex Shedding ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Closed Cavity ◽  
Time Exposure ◽  
Starting Flow ◽  
Visualization Techniques ◽  
Insight Into

Using a variety of flow-visualization techniques, the flow behind a circular cylinder has been studied. The results obtained have provided a new insight into the vortex-shedding process. Using time-exposure photography of the motion of aluminium particles, a sequence of instantaneous streamline patterns of the flow behind a cylinder has been obtained. These streamline patterns show that during the starting flow the cavity behind the cylinder is closed. However, once the vortex-shedding process begins, this so-called ‘closed’ cavity becomes open, and instantaneous ‘alleyways’ of fluid are formed which penetrate the cavity. In addition, dye experiments also show how layers of dye and hence vorticity are convected into the cavity behind the cylinder, and how they are eventually squeezed out.

Inviscid Model of Two-Dimensional Vortex Shedding by a Circular Cylinder

AIAA Journal ◽  
1979 ◽  
Vol 17 (11) ◽  
pp. 1193-1200 ◽  
Author(s):  
Turgut Sarpkaya ◽  
Ray L. Schoaff
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Two Dimensional

Two-dimensional vortex shedding of a circular cylinder

2001 ◽  
Vol 13 (3) ◽  
pp. 557-560 ◽  
Author(s):  
C.-Y. Wen ◽  
C.-Y. Lin
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Two Dimensional

Numerical Simulation of Flow over a Circular Cylinder at Low Reynolds Number

2011 ◽  
Vol 255-260 ◽  
pp. 942-946
Author(s):  
Hua Bai ◽  
Jia Wu Li
Keyword(s):  
Numerical Simulation ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Medial Axis ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Control Measures ◽  
Hydrodynamic Characteristics ◽  
Two Dimensional

The hydrodynamic characteristics of a circular cylinder in two-dimensional unsteady uniform cross flow was simulated numerically by the laminar model with the reasonable mesh used the method of fluent. The focus of this numerical simulation was to research the characteristics of pressure distribution, drag coefficient and lift coefficient, and the Strouhal number was calculated at Reynolds-numbers value of 200. The results agree well with experimental data and other numerical results according to the reference. In order to study the control measures of the flow over a circular cylinder, the different baffles inserted at various locations downstream of the cylinder have been compared. The results shows that the vortex shedding of flow over a circular cylinder could be well controlled by place the baffle at a right position of the downstream medial axis of the cylinder, which could reduce drag and resist vibration.

Effect of Fins on Vortex Shedding Noise Generated From a Circular Cylinder in Cross Flow

2010 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Yuji Kouno ◽  
Eiichi Nishida
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Finned Tube ◽  
Pressure Level ◽  
Spanwise Direction ◽  
Equivalent Diameter ◽  
Karman Vortex ◽  
Bare Tube

In the present paper, the effect of twist-serrated fins around a bare tube on the Aeolian tone was experimentally investigated. These fins were mounted spirally around a bare tube and had the same geometry as those actually used in boiler tubes. We measured the intensity of velocity fluctuation, spectrum of velocity fluctuation, coherence of Karman vortex in the spanwise direction, dynamic lift force, and sound pressure level of the aerodynamic noise generated from finned tubes with various fin pitches. An Aeolian tone induced by Karman vortex shedding was observed in the case of a finned tube, although the complicated fin was mounted around a bare tube. A decrease in the pitch of the fin effectively caused an increase in the equivalent diameter, which acted as the characteristic length of a cylinder with fins. The equivalent diameter depended on the Reynolds number. We modified a relation to calculate the characteristic diameter of the finned tube, which in turn was used to calculate the Strouhal number. The coherent scales in the spanwise direction for the cases with various fin pitches were slightly larger than that of a simple circular cylinder. It is known that the sound pressure level of the Aeolian tone depends on the coherent scale of the Karman vortex in the spanwise direction. However, when the pitch of the fins decreased, the peak level of the sound pressure spectrum decreased. A correlation analysis between the flow field and Aeolian tone was carried out.

Numerical analysis of two-dimensional motion of a freely falling circular cylinder in an infinite fluid

2008 ◽  
Vol 604 ◽  
pp. 33-53 ◽  
Author(s):  
KAK NAMKOONG ◽  
JUNG YUL YOO ◽  
HYOUNG G. CHOI
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Velocity Vector ◽  
Density Ratio ◽  
Transverse Motion ◽  
Stream Velocity ◽  
Gravitational Acceleration ◽  
Two Dimensional

The two-dimensional motion of a circular cylinder freely falling or rising in an infinite fluid is investigated numerically for the range of Reynolds number Re, < 188 (Galileo number G < 163), where the wake behind the cylinder remains two-dimensional, using a combined formulation of the governing equations for the fluid and the dynamic equations for the cylinder. The effect of vortex shedding on the motion of the freely falling or rising cylinder is clearly shown. As the streamwise velocity of the cylinder increases due to gravity, the periodic vortex shedding induces a periodic motion of the cylinder, which is manifested by the generation of the angular velocity vector of the cylinder parallel to the cross-product of the gravitational acceleration vector and the transverse velocity vector of the cylinder. Correlations of the Strouhal–Reynolds-number and Strouhal–Galileo-number relationship are deduced from the results. The Strouhal number is found to be smaller than that for the corresponding fixed circular cylinder when the two Reynolds numbers based on the streamwise terminal velocity of the freely falling or rising circular cylinder and the free-stream velocity of the fixed one are the same. From numerical experiments, it is shown that the transverse motion of the cylinder plays a crucial role in reducing the Strouhal number. The effect of the transverse motion is similar to that of suction flow on the low-pressure side, where a vortex is generated and then separates, so that the pressure on this side recovers with the vortex separation retarded. The effects of the transverse motion on the lift, drag and moment coefficients are also discussed. Finally, the effect of the solid/fluid density ratio on Strouhal–Reynolds-number relationship is investigated and a plausible correlation is proposed.

Numerical Analysis of Sound Generation by a Two-Dimensional Cylinder in a Uniform Flow

2003 ◽  
Author(s):  
Ayaka Imamura ◽  
Nozomu Hatakeyama ◽  
Osamu Inoue
Keyword(s):  
Sound Pressure ◽  
Stokes Equations ◽  
Sound Field ◽  
Uniform Flow ◽  
Navier Stokes ◽  
Pressure Waves ◽  
Two Dimensional ◽  
Sound Generation ◽  
Navier Stokes Equations ◽  
Characteristic Features

The sound generated by a squarer cylinder in a uniform flow is investigated by direct numerical simulation of the two-dimensional compressible Navier–Stokes equations. The characteristic features of the generated sound are investigated and compared for different configurations and angles of attack. Results show that sound pressure waves are generated by vortex shedding from the cylinder into its wake. The sound field is dominated by lift dipole. The effect of the angle of attack on the sound generation and propagation is also analyzed.

scholarly journals Possibilities of ultrasound methods in the diagnosis of decompression sickness

2022 ◽  
Vol 7 (4) ◽  
pp. 75-83
Author(s):  
D. P. Zverev ◽  
S. A. Bychkov ◽  
A. A. Myasnikov ◽  
A. M. Yarkov ◽  
A. B. Khaustov ◽  
...  
Keyword(s):  
Doppler Effect ◽  
Ultrasound Examination ◽  
Decompression Sickness ◽  
Two Dimensional ◽  
Right Heart ◽  
Gas Formation ◽  
The Doppler Effect ◽  
Dimensional Echocardiography ◽  
The Right ◽  
Two Dimensional Echocardiography

Aim of the work: to conduct a comparative analysis of methods of ultrasound examination of the right heart with audio and visual indication of intravascular decompression gas formation in divers after diving.Materials and methods. An examination of the right heart in divers after 152 man-descents was carried out. Intravascular decompression gas production was assessed by ultrasound using sound location based on the Doppler effect and transthoracic two-dimensional echocardiography.Results and discussion. Both methods make it possible to determine intravascular decompression gas formation after a diving descent, correlate with the clinical picture of acute decompression sickness and should be used in the medical support of diving descents. At the same time, the method of ultrasound examination based on transthoracic two-dimensional echocardiography turned out to be more sensitive in determining gas bubbles in the right heart as compared to auditory location with the Doppler effect.

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