• Title/Summary/Keyword: Circular Cylinder

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An Experimental Study on Swirling Flow behind a Round Cylinder in the Horizontal Circular Tube

  • Chang Tae-Hyun;Lee Hae Soo
    • Journal of Mechanical Science and Technology
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    • v.19 no.12
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    • pp.2270-2280
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    • 2005
  • An experimental study is performed for turbulent swirling flow behind a circular cylinder using 2-D PIV technique. The Reynolds number investigated are 10,000, 15,000, 20,000 and 25,000. The mean velocity vector, time mean axial velocity, turbulence intensity, kinetic energy and Reynolds shear stress behind the cylinder are measured before and behind the round cylinder along the test tube. A comparison is included with non swirl flow behind a circular and square cylinder. The recirculation zones are showed asymmetric profiles.

The Magnus Efface of a Rotating Circular Cylinder Near a Plane Wall (벽면 근처에서 회전하는 원주의 마그너스 효과)

  • Ro, Ki-Deok;Kim, Kwang-Seok;Oh, Se-Kyeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.11
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    • pp.957-962
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    • 2007
  • The flow around a rotating circular cylinder near a plane wall is investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters are the rotating direction of the cylinder, the space ratios H/D($H/D=0.05{\sim}0.5$) between cylinder and plane wall and the velocity ratios ${\alpha}({\alpha}=0{\sim}{\pm}2.0)$. In the case of clockwise, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise, the absolute value of the lift on the rotating circular cylinder was increased with the space ratios and with the velocity ratios, the lower separation point was more shifted in the rotating direction with them.

Characteristics of Vortex Shedding behind a Circular Cylinder with Serrated Fins (Serrated Fin이 부착된 튜브의 와유출특성 연구)

  • Ryu, Byong-Nam;Kim, Kyung-Chun;Boo, Jung-Sook
    • Proceedings of the KSME Conference
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    • 2001.06e
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    • pp.570-575
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    • 2001
  • An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds numbers. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.

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Characteristics of Vortex Shedding behind a Circular Cylinder with Serrated Fins (톱니형 핀이 부착된 튜브의 와유출특성 연구)

  • Bu, Jeong-Suk;Ryu, Byeong-Nam;Kim, Gyeong-Cheon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.8
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    • pp.1077-1086
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    • 2001
  • An experimental study is performed to investigate the characteristics of vortex shedding behind a circular cylinder with serrated fins using hot-wire anemometer. Strouhal numbers which are calculated using outer diameter of a circular cylinder with serrated fins are higher than that of a circular cylinder. Fin thickness and pitch are closely related with vortex shedding frequency and play increasing or decreasing vortex shedding after transient Reynolds number. Strouhal numbers using effective diameters which are proposed in this paper agree with that of a circular cylinder. After transient Reynolds number, a trend of Strouhal number can be estimated by checking the ratio of effective diameter to inner diameter.

THERMAL STRESSES IN A SEMI-INFINITE SOLID CYLINDER SUBJECTED TO INTERNAL HEAT GENERATION

  • DESHMUKH, KISHOR CHINTANAMRAO;QUAZI, YUSUF IQBAL
    • Communications of the Korean Mathematical Society
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    • v.30 no.4
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    • pp.505-513
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    • 2015
  • The present paper deals with the determination of displacement and thermal stresses in a semi-infinite circular cylinder defined as $0{\leq}r{\leq}b$, $0{\leq}z<{\infty}$, due to internal heat generation within it. A circular cylinder is considered having arbitrary initial temperature and subjected to time dependent heat flux at the fixed circular boundary (r = b) whereas the zero temperature at the lower surface (z = 0) of the semi-infinite circular cylinder. The governing heat conduction equation has been solved by using integral transform method. The results are obtained in series form in terms of Bessel functions. The results for displacement and stresses have been computed numerically and illustrated graphically.

Flow Control of Turbulent Wake Behind a Circular Cylinder Using a Self-adjusting Rod (자율 제어봉을 이용한 실린더 후류의 유동제어에 관한 연구)

  • Lim Hee Chang;Kam Dong Hyuk;Lee Sang Joon
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.467-470
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    • 2002
  • The offects of a small control rod (d=3mm) located near a main circular cylinder on the drag reduction and wake structure modification were investigated. The location of the small control rod mounted on a rod-like spring is self-adjusting according to the wake structure far optimal control of the flow around the main cylinder. The experiments were carried out at the Reynolds numbers based on the cylinder diameter (D=50mm) in the range $Re_{D}=1{\times}10^4{\~}6{\times}10^4$. Mean velocity and turbulent statistics were measured with varying the angle along the cylinder circumference ${\Theta}=15^{\circ},\;30^{\circ},\;45^{\circ}$ and the distance between the main and control rods L =0.7, 1. Compared with the bare cylinder, the main circular cylinder with the fixed and self-adjusting rods reduced drag coefficient by $10{\%}$ at the angle of ${\Theta}=45^{\circ}$. For the main cylinder with self-adjusting rot as the Reynolds numbers increase, the streamwise mean velocity is increased, however, the turbulence intensity is decreased. In addition, the control rods tested in this study are effective at higher Reynolds number than at lower Reynolds number.

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Numerical Study on the Motion Characteristics of a Freely Falling Two-Dimensional Circular Cylinder in a Channel (채널 내 자유 낙하하는 2차원 원형 실린더의 운동 특성에 관한 수치적 연구)

  • Jeong, Hae-Kwon;Yoon, Hyun-Sik;Ha, Man-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.7
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    • pp.495-505
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    • 2009
  • A two-dimensional circular cylinder freely falling in a channel has been simulated by using immersed boundary - lattice Boltzmann method (IB-LBM) in order to analyze the characteristics of motion originated by the interaction between the fluid flow and the cylinder. The wide range of the solid/fluid density ratio has been considered to identify the effect of the solid/fluid density ratio on the motion characteristics such as the falling time, the transverse force and the trajectory in the streamwise and transverse directions. In addition, the effect of the gap between the cylinder and the wall on the motion of a two-dimensional freely falling circular cylinder has been revealed by taking into account a various range of the gap size. As the cylinder is close to the wall at the initial dropping position, vortex shedding in the wake occurs early since the shear flow formed in the spacing between the cylinder and the wall drives flow instabilities from the initial stage of freely falling. In order to consider the characteristics of transverse motion of the cylinder in the initial stage of freely falling, quantitative information about the cylinder motion variables such as the transverse force, trajectory and settling time has been investigate.

A Study on the Flow=Induced Vibration of Tube Array in Uniform Crossflow(II) On the Flow-Induced Vibration of Two Interfering Circular Cylinders in Tandem (균일 유동장내 튜브배열의 유동관련 진동에 관한 연구( II ) 직렬로 배열된 두 원주의 유동여기 진동에 관하여)

  • 이기백;김봉환;양장식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.6
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    • pp.1518-1528
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    • 1993
  • The wake-induced vibration and proximity-induced vibration of two interfering circular cylinders in tandem are investigated experimentally, using an elastically supported cylinder and a fixed cylinder in uniform crossflow. Dynamic responses and flow periodicity in wake are measured to investigate the effect of system parameters on aerodynamic instability. The parameters include the free stream wind velocity and the position of two interfering circular cylinders. The oscillating behavior of the amplitude of the elastically supported cylinder is changed by varying the position, the relative gap spacing between two interfering circular cylinders and the reduced velocities. In small gap spacing between the elastically supported cylinder located to upstream and the circular cylinder fixed to downstream, the fluidelastic instability is founded. The vibration amplitude decreases notably as gap spacing between two interfering circular cylinders becomes large. The dynamic behavior at g/D-4.0 is similar to that of the single circular cylinder.

A Study on Frequency Characteristics of Wake Flow a Circular Cylinder with Control Cylinder (제어봉이 부착된 원관 후류의 주파수특성에 관한 연구)

  • Choe, Sang-Bom;Han, Won-Hui;Cho, Dae-Hwan;Gim, Ok-Sok
    • Proceedings of KOSOMES biannual meeting
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    • 2007.11a
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    • pp.177-183
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    • 2007
  • Flow characteristics of the cylinder wake controlled with a small control cylinder were experimentally investigated by the PN (Particle Image Velocimetry) technique. Flow visualization of the flow around a circular cylinder was conducted in the Circulating Water Channel. The control cylinder having diameter of d=5mm, 10mm and 20mm was installed behind a circular cylinder of D=50mm. And the Reynolds number were $Re=4.9{\times}10^3,\;Re=9.9{times}10^3$ and $Re=1.9{\times}10^4$. In this study, the frequency characteristics of the controlled wake were analyzed by using spectral analysis of the measured wake velocity signals. As a result, the controlled wake had smaller vortex shedding frequency than that of circular cylinder wake by the effect of the control cylinder. Governing parameters of the flow control were d/D, and Reynolds number and they largely influenced the frequency characteristics of the cylinder wake. And vortex shedding frequency appeared most lowly at d=0.2D

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Extraction of Wave Energy Using the Coupled Heaving Motion of a Circular Cylinder and Linear Electric Generator (원기둥과 선형발전기의 연성 수직운동을 이용한 파 에너지 추출)

  • Cho, Il-Hyoung;Kweon, Hyuck-Min
    • Journal of Ocean Engineering and Technology
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    • v.25 no.6
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    • pp.9-16
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    • 2011
  • The feasibility of wave energy extraction from a heaving truncated cylinder and the corresponding response of the linear electric generator (LEG) composed of spring, magnet, and coil has been investigated in the frame of three-dimensional linear potential theory. The heaving motion of a circular cylinder is calculated by means of the matched eigenfunction expansion method. Further, the analytical results are validated by numerical results using the ANSYS AQWA commercial code. By the action of a heaving circular cylinder, the magnet suspended by a spring can slide vertically inside the heaving cylinder. The mechanical power is extracted from the magnet motion relative to the coil/stator which is attached to the cylinder. The coupled ODE of a heaving cylinder and LEG system in waves is derived to obtain the magnet motion relative to a cylinder. To maximize the relative motion of the magnet, both the buoy draft and the LEG system parameters (spring stiffness, damping) should be selected properly for generating the double resonance considering the peak frequency of the target spectrum.