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Volume 1988 (1988)
- Issue 37 Pages 73-
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Volume 1988, Issue 37
Displaying 1-8 of 8 articles from this issue
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K. FUJITA, Y. IKEGAMI, K. KOBAYASHI, M. OHASHI1988 Volume 1988 Issue 37 Pages 73-82
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSVortex shedding vibration is one of the most important problems to consider in the design of circular cylindrical structures such as the thermowell, the thimble tube for the ICIS and the support columns in nuclear reactors. The objectives of this study are to investigate the vibration response of these structures due to cross flaw aver the range of the high Reynolds numbers, and to propose suggestions to guide future designs of these structures. Experimental studies on the fluctuating lift force which acts on a single circular cylinder for the Reynolds numbers from 3x104 to 3x106 were conducted in a MEI waterchannel test apparatus. The tests were carried out by using two types of models with different stiffness characteristics. One was a stationary model which was used to measure the fluctuating lift force and the Strouhal number. The other was an elastic model which wasused to investigate the vibration response. The results obtained using these two models were a lift coefficient of CL rms and a Strouhal number of st. These results were the same values which have previously been reported by many other investigators. The “locked-in” vibration observed with the elastic model for the critical Reynolds number range was the same phenomena found in the subcritical Reynolds number range.View full abstractDownload PDF (1582K) -
Y. UEMATSU, M. YAMADA, K. ISHII1988 Volume 1988 Issue 37 Pages 83-92
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSFlow around a cantilevered circular cylinder has been studied experimentally in the subcritical and critical Reynolds-number ranges. Particular attention was paid to the free-stream turbulence effects on the steady aerodynamic characteristics of the cylinder. Measurements were made of the surface pressure distribution, flow separation line and vortex shedding frequency in gridgenerated turbulent flows. The aerodynamic characteristics of a cylinder were only minutely affected by the free-stream turbulence in the subcritical flaw. The critical Reynolds number was expressed as a function of the Taylor number Tx defined in terms of the longitudinal integral scale of the free-stream turbulence. The mean drag coefficient and the position of the flow separation point were fairly well-correlated with the parameter Re1.34.Tx, with Re being the Reynolds number. Furthermore, it was found that some steady aerodynamic coefficients of the cylinder were closely correlated among themselves.View full abstractDownload PDF (2137K) -
M.M. Zdravkovich1988 Volume 1988 Issue 37 Pages 93-102
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSFlow around a circular cylinder is governed by three transitions: in-the-near-wake, along the free shear layers and along the boundary layers. Each transition is characterized by several flow regimes which are sensitive to disturbances. The variation of mean and fluctuating lift and drag coefficients, friction and pressure coefficients are compiled in the range 100 < Re < 108 for the disturbance-free flow.
The concept of possible inversion of influencing to governing parameters and vice versa is applied to rough cylinders and turbulent flow. The free stream turbulence and surface roughness affect differently the three transitions and may cause an obliteration of some flow regimes in addition to moving the transition state as a whole to lower Reynolds numbers.View full abstractDownload PDF (2030K) -
M. MATSUMOTO, N. SHIRAISHI, M. KITAZAWA, C. KNISELY, H. SHIRATO, Y. KI ...1988 Volume 1988 Issue 37 Pages 103-112
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSThis study attempts to clarify of the mechanism of rain-wind induced vibration of the stay cables of a cable stayed bridge and to find an effective aerodynamic stabilization method. Through a series of wind tunnel tests the fundamental aerodynamic characteristics of a yawed and/or inclinedcircular cylinder withand without rain were investigated. An intense secondaryaxial flow was found to form in the early wake, playing a similar role to that of a splitter plate submergedinthe wake. This axial flow resulted inanaerodynamic exciting force acting onthe yawed and/or the inclined circular cylinder. The role of rain in the rain-wind induced vibration of the stay cable is shown to be that of an amplifier of the essential, unstable aerodynamic characteristics of the yawed and/or the inclined circular cylinder. Aerodynamic stabilization should depend essentially on controlling this characteristic secondary flow.View full abstractDownload PDF (2037K) -
H. YAMAGUCHI1988 Volume 1988 Issue 37 Pages 113-120
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSThe fundamental growth mechanism of rain vibration of cable in cable-stayed bridges are studied analytically. It has been reported by Hikami and Shiraishi [1987] that the rain vibration is a large amplitude oscillation caused by the combined influence of rain and wind, and that the rain water rivulet formed along the upper surface of cable is the origin of rain vibration. Therefore, a cylinder of figure-8 cross section is adopted as an analytical model for the rain vibration of cable with upper rivulet. The characteristics of unsteady wind forces of the figure-8 section model are investigated first through wind tunnel experiments. Two possible mechanisms are, then, checked for rain vibration by means of quasi-steady galloping analysis; one is Den Hartog mechanism of cable oscillation and another is the two-degree-of-freedom instability, i.e. the torsional mechanism, caused primarily by the circumferential oscillation of the rivulet along cable surface. It is found that the oscillation of upper rivulet, the fundamental frequency of which could coincide with the natural frequency of cable motion at the wind speed around 10 m/s, is aerodynamically coupled with the flexural oscillation of cable, and that this coupled motion of rivulet makes the modal aerodynamic damping negative. That is, it is concluded that the circumferential oscillation of the upper rivulet is indispensable to the growth of rain vibration.View full abstractDownload PDF (1852K) -
C.W. KNISELY, M. KAWAGOE1988 Volume 1988 Issue 37 Pages 121-130
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSThe static lift force (resulting from static displacement) and the dynamic lift force (resulting from forced vibration) acting on the downstream member of a pair of slightly staggered tandem cylinders in a free-surface water channel flow were measured. The downstream cylinder could undergo transverse forced vibrations while the upstream cylinder remained fixed. The motivation of this study was to obtain reasonable estimates for the phase lag, or delay time, between cylinder motion and the dynamic lift force acting on the oscillating downstream cylinder when it undergoes interference galloping. A preliminary empirical correlation of delay time with a dimensionless parameter, which is the product of the reduced velocity and the square root of the nondimensional amplitude of cylinder motion, is presented. A comparison of the dynamic force-displacement diagrams with the force displacement diagrams derived by a time-delayed quasisteady model reveals that even the time-delayed quasi-steady analysis cannot accurately reproduce the dynamic loading of the vibrating cylinder. However, the force-displacement diagrams from the quasi-steady analysis appear to qualitatively resemble the dynamically recorded force-displacement diagrams, especially at higher reduced velocities, perhaps explaining the success of the time-delayed quasi-steady model in predicting a first estimate of the onset velocity for interference galloping.View full abstractDownload PDF (2369K) -
M. Matsumoto, N. Shiraishi, H. Shirato1988 Volume 1988 Issue 37 Pages 131-140
Published: October 15, 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSThe aerodynamic, or more generally fluid-dynamic, instability of the downstream circular cylinder in the wake of a similar cylinder in subcritical flow is the focal point of this paper. These phenomena are known to cause fatigue problems and impair the serviceability and safety of structures in various engineering fields. The aim of this study is to clarify the mechanism of this phenomena, as well as to find the conditions under which vibrations occur. A series of wind tunnel experiments and corresponding flow visualization in a water flume were conducted to permit discussion of the unsteady pressure properties, the aerodynamic unsteady force characteristics including its nonlinearity, and their relationship to the flow patterns.
The sudden decrease in pressure on the inward surface of the downstream cylinder when it approaches the upstream one, appears to play an important role in the vibration. Furthermore, an analogy between the unsteady aerodynamic force properties of the downstream cylinder and those of an isolated bluff body which undergoes both torsional and coupled flutter is postulated.View full abstractDownload PDF (2221K) -
1988 Volume 1988 Issue 37 Pages 691
Published: 1988
Released on J-STAGE: September 28, 2010
JOURNAL FREE ACCESSDownload PDF (57K)
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