The Role of Axial Flow in Near Wake on the Cross-Flow Vibration of the Inclined Cable of Cable-Stayed Bridges

2010 ◽  
Author(s):  
Masaru Matsumoto
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Axial Flow ◽  
Splitter Plate ◽  
Near Wake ◽  
Karman Vortex ◽  
The Cross ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

Nowadays, the violent wind-induced vibration, including “rain-wind induced vibration” and “dry-galloping”, of stay-cables of cable-stayed bridges has become the most serious issue for bridge design. Up-to-date, the major factors for excitation of inclined cables have been clarified to be, for “rain-wind” induced vibration, the formation of “water-rivulet” on the particular position of upper cable surface, and, for “dry galloping”, the “axial flow” which flows in the near wake along cable-axis, and the effect of drag-force associated with Reynolds number, separately. However, the details of the effect of “axial flow” remain unsolved. Thus, this study aims to clarify the effect of axial flow in near wake on the aero-elastic vibration of inclined cables basing on various experiments. The mean velocity of axial flow was almost 60% of approaching wind velocity. Furthermore, the aerodynamic effect of the “axial flow” on cross-flow vibration of inclined cables is discussed in relation to the mitigation of Karman vortex shedding in near wake. Since the role of axial flow seems to be similar to the splitter plate installed in wake from the point of mitigation of Karman vortex shedding, to clarify the cross-flow response in relation to the mitigation of Karman vortex, the perforated ratio of the splitter plate was variously changed, then the similarity of effect of axial flow and the one of splitter plate was verified comparing their unsteady lift force-characteristics. In summary, it is shown that the axial flow on aerodynamic cross-flow vibration might excite like galloping similarly with the splitter plate by mitigation of Karman vortex.

Characteristics of Aerodynamic Sound Radiated From Two Finned Cylinders

2014 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Hiroki Matsuoka ◽  
Kazuki Hosokai ◽  
Eiichi Nishida ◽  
Eru Kurihara
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Transverse Direction ◽  
Flow Direction ◽  
Cross Flow ◽  
Near Wake ◽  
Aerodynamic Sound ◽  
Spacing Ratio ◽  
Staggered Arrangement ◽  
Karman Vortex

In the present paper the attention is focused on the characteristics of aerodynamic sound radiated from two finned cylinders with tandem and staggered arrangement exposed to cross-flow. We measured the spectrum of SPL and flow velocity for the cylinder spacing ratios ranged from 0 to 1.05 in the transverse direction and the ratios from 1.24 to 6.8 in the flow direction at Reynolds number of 1.0×105−1.9×105. As a result, we found that the peak SPL and Strouhal number of vortex shedding for two finned cylinders depend on the cylinder spacing ratios as well as those for bare cylinders. The peak SPL of the spectrum varied complexly with the tube spacing ratio. The peak levels of SPL for tandem finned cylinders were approximately 8 dB lower than that for the tandem bare cylinders. At the cylinder spacing ratio of 1.24 in the flow direction, the peak SPL for two finned cylinders at the cylinder spacing ratio of 0.72 in the transverse direction was about 8 dB larger than that for tandem finned cylinders. The peak SPL depended on the spanwise correlation length of the Karman vortex formed in the near wake of the downstream of two finned cylinders.

Vortex Formation in the Wake of a Vibrating, Flexible Cable

1974 ◽  
Vol 96 (4) ◽  
pp. 317-322 ◽  
Author(s):  
S. E. Ramberg ◽  
O. M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Hot Wire ◽  
Near Wake ◽  
Formation Region ◽  
Vortex Streets ◽  
Region Length ◽  
Karman Vortex ◽  
Flexible Cables

The von Karman vortex streets formed in the wakes of vibrating, flexible cables were studied using a hot-wire anemometer. All the experiments took place in the flow regime where the vibration and vortex-shedding frequencies lock together, or synchronize, to control the wake formation. Detailed measurements were made of the vortex formation flow for Reynolds numbers between 230 and 650. As in the case of vibrating cylinders, the formation-region length is dependent on a shedding parameter St* related to the natural Strouhal number and the vibrational conditions. Furthermore, the near wake configuration is found to be dependent on the local amplitude of vibration suggesting that the vibrating cylinder rseults are directly applicable in that region.

Role of dynamic water rivulets in the excitation of rain–wind-induced cable vibration: A critical review

2021 ◽  
pp. 136943322110401
Author(s):  
Donglai Gao ◽  
Wenjie Li ◽  
Haiquan Jing ◽  
Jian Wang ◽  
Jintuan Wu ◽  
...  
Keyword(s):  
Wind Engineering ◽  
Excitation Mechanism ◽  
Structure Interaction ◽  
Wall Boundary Layer ◽  
Stay Cables ◽  
Considerable Research ◽  
Complex Fluid ◽  
Wind Induced Vibration ◽  
Cable Stayed Bridges

It has been more than 30 years since Hikami Y and Shiraishi N (1988) Rain–wind-induced vibrations of cable-stayed bridges. Journal of Wind Engineering and Industrial Aerodynamics 29: 409–418 first reported the rain–wind-induced vibration (RWIV) of stay cables in the construction stage of Meikonishi Bridge, Japan. After that, considerable research efforts have been devoted to understanding the RWIV of stay cables, and the role of the upper rivulet has been gradually realized and studied. This study presents a selective review on recent progress of RWIV and its controversial excitation mechanism. The available knowledge and up-to-date understanding of this complex fluid-structure interaction are presented in some detail. The formation, dynamics of water rivulet, and its role in affecting the near-wall boundary layer properties and in the excitation scenario of RWIV are of particular interest in this study. Finally, some limitations of previous studies are concluded, with some perspective suggestions for further study of excitation mechanism of RWIV.

814 Effect of fin around a circular cylinder on Karman vortex shedding in cross flow

2007 ◽  
Vol 2007 (0) ◽  
pp. _814-1_-_814-4_
Author(s):  
Hiromitsu HAMAKAWA ◽  
Tomohiro KUDO ◽  
Eiichi NISHIDA ◽  
Tohru FUKANO
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Karman Vortex

Synchronized Vibrations of a Circular Cylinder in Cross Flow at Supercritical Reynolds Numbers1

2003 ◽  
Vol 125 (1) ◽  
pp. 97-108 ◽  
Author(s):  
Tsutomu Kawamura ◽  
Toshitsugu Nakao ◽  
Masanori Takahashi ◽  
Masaaki Hayashi ◽  
Kouichi Murayama ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Excited Vibration ◽  
Karman Vortex ◽  
Lock In

Synchronized vibrations of a circular cylinder in a water cross flow at supercritical Reynolds numbers were measured. Turbulence intensities were varied to investigate the effect of the Strouhal number on the synchronization range. Self-excited vibration in the drag direction due to symmetrical vortex shedding began only when the Strouhal number was about 0.29, at a reduced velocity of 1.1. The reduced velocities at the beginning of lock-in vibrations caused by Karman vortex shedding decreased from 1.5 to 1.1 in the drag direction and from 2.7 to 2.2 in the lift direction, as the Strouhal number increased from 0.29 to 0.48.

Simulation of Cross-Flow Vortex-Induced Vibration of Single Tube Based on Two-Way Fluid-Solid Interaction Method

2017 ◽  
Author(s):  
Wang Zengzeng ◽  
Lu Tao ◽  
Liu Bo
Keyword(s):  
Nuclear Fuel ◽  
Vortex Shedding ◽  
Vibration Frequency ◽  
Cross Flow ◽  
Time History ◽  
Pressurized Water ◽  
Vortex Induced Vibration ◽  
The Cross ◽  
Control Equation ◽  
Fluid Solid Interaction

The fatigue damage and lift force caused by vortex induced vibration occur very often in the core of the Pressurized Water Reactor (PWR) [1] It is extremely complex to illustrate the mechanism of vibration which induced by Cross-flow. With the spacer grids and wings, the flow direction which in axial direction at the inlet will change and create swirls, so there are many flow directions in the nuclear fuel component. Assumed the tube endure cross-flow only in this article to simplify the fluid model. Most researchers in this field often ignore the displacement of structure induced by the cross flow because the value is so small that not enough to change the fluid region. In truth conditions, the motion of the cylinder caused the wake oscillation and strengthen the vortex shedding, in turn, the vortex shedding will aggravate the vibration amplitude. According that, one way FSI (Fluid Solid Interaction) can’t capture the influence from the cylinder vibration. In this article, Two-way FSI method was executed to get the vibration in time history in order to get the random vibration induced by the cross flow more close to the actual project. Using Finite Volume Method to discrete the fluid control equation and finite element method to discrete structure control equation combined with moving mesh technology. An interface between the fluid region and the structure region was created to transfer the fluid force and the structure displacement. Coupling CFD code and CSD (Computational Solid Dynamics) code to solve the differential equation and obtain the displacement of the cylinder in time history. A Fast Fourier Transfer (FFT) has been done to get the vibration frequency. An Analysis of the vortex shedding frequency and vibration frequency to find the correlation between the vortex shedding and the vibration frequency has been done. A modal analysis for the cylinder without water has been done to get the natural frequency. Results shows the cylinder has different response to the vortex shedding at different position of the cylinder in the same condition. There are more works need to be done aim to get the vibration mechanism in tandem tube and parallel tube to get clearly mechanism of vortex induced vibration in nuclear fuel assembly. The research of the vortex induced vibration in this article is a key to get on the follow research in more tubes array in different methods.

What is the Role of the Stagnation Region in Karman Vortex Shedding?

2011 ◽  
Vol 18 (3) ◽  
pp. 361-370 ◽  
Author(s):  
Grzegorz Pankanin
Keyword(s):  
Vortex Shedding ◽  
Bluff Body ◽  
Flow Visualisation ◽  
Information Channel ◽  
Hot Wire ◽  
Stagnation Region ◽  
Karman Vortex ◽  
Experimental Findings ◽  
The Relationship

What is the Role of the Stagnation Region in Karman Vortex Shedding?This paper is devoted to the problem of the appearance of a stagnation region during Karman vortex shedding. This particular phenomenon has been addressed by G. Birkhoff in his model of vortices generation. Experimental results obtained by various research methods confirm the existence of a stagnation region. The properties of this stagnation region have been described based on experimental findings involving flow visualisation and hot-wire anemometry. Special attention has been paid to the relationship between the existence of a slit in the bluff body and the size of the stagnation region. The slit takes over the role of the stagnation region as an information channel for generating vortices.

An Experimental Study of the Flow Above the Free Ends of Surface-Mounted Bluff Bodies

2012 ◽  
Author(s):  
Noorallah Rostamy ◽  
David Sumner ◽  
Donald J. Bergstrom ◽  
James D. Bugg
Keyword(s):  
Boundary Layer ◽  
Flow Pattern ◽  
Vortex Shedding ◽  
Ground Plane ◽  
Separated Flow ◽  
The Body ◽  
Bluff Bodies ◽  
Near Wake ◽  
Square Prism ◽  
Karman Vortex

The flow around surface-mounted finite-height bluff bodies is more complex than the flow around a two-dimensional or “infinite” cylinder. The flow over the free end and the boundary layer flow around the body-wall junction strongly influence the near-wake flow pattern. Streamwise tip vortex structures interact in a complex manner with Kármán vortex shedding from the sides of the body, and are responsible for a downward-directed local velocity field in the upper part of the wake known as “downwash.” A second pair of streamwise vortex structures, known as the base vortices, is found close to the ground plane. Upstream of the body the familiar horseshoe vortex is found. The interactions between the tip vortices, base vortices, and Kármán vortex shedding are strongly influenced by the aspect ratio, AR = H/D (for height, H, and width, D), the Reynolds number, Re, and the relative thickness of the boundary layer, δ/D. The flow above the free ends of surface-mounted finite-height circular cylinders and square prisms was studied in a low-speed wind tunnel using particle image velocimetry (PIV). Cylinders and prisms of AR = 9, 7, 5, and 3 were tested at Re = 4.2 × 104. The bodies were mounted normal to a ground plane and were partially immersed in a turbulent flat-plate boundary layer with δ/D = 1.7. PIV measurements were made above the free ends in three vertical planes at different cross-stream locations (y/D = 0, 0.25, and 0.375). The ensemble-averaged streamlines, turbulence intensity and Reynolds shear stress fields were obtained in these planes. The PIV results provide insight into the separated flow above the free ends, including the effects of AR and body shape. For the finite square prism, the large, separated, recirculating flow region extends into the near-wake. For the finite circular cylinder, this region is smaller and the separated flow reattaches onto the free-end surface. For the square prism of AR = 3, considerable difference is seen in the free-end flow pattern compared to the more slender prisms of AR = 9, 7 and 5. In particular, a cross-stream vortex is formed due to interaction between the separated flow from the leading edge of the prism and the reverse flow over the free end. This vortex is seen in all three planes for AR = 3 but only in the symmetry plane for AR = 9, while for the finite circular cylinder the flow pattern above the free end seems to be the same in all three planes for all aspect ratios, consisting of a cross-stream vortex at approximately x/D = 0.

Vortex Shedding From Trailing Edge of Rotor Blade of Axial Flow Fan at Design Operating Condition

2015 ◽  
Author(s):  
Hiromitsu Hamakawa ◽  
Kaisei Oda ◽  
Yuta Asai ◽  
Kazuki Hosokai ◽  
Eru Kurihara ◽  
...  
Keyword(s):  
Vortex Shedding ◽  
Velocity Fluctuation ◽  
Rotor Blade ◽  
Time Lag ◽  
Axial Flow ◽  
Rotational Axis ◽  
Trailing Edge ◽  
Velocity Fluctuations ◽  
Operating Condition ◽  
Karman Vortex

In the present paper the attention is focused on the vortex shedding from the trailing edge of the rotor blade at the design operating condition. We measured the relative velocity, the turbulence intensity, the spectrum of velocity fluctuation and the in-phase velocity fluctuation near the trailing edge along the blade span. The time variations of amplitude of velocity fluctuations from 1500 Hz to 1900 Hz in the wake of the suction and pressure side of the trailing edge are out of phase with each other simultaneously at the mid span region. Karman vortices were formed in the near wake of the trailing edge of rotor blade intermittently. As the distance between two measured locations along the blade span increased, the in-phase rate of two velocity fluctuations decreased. This rate became maximum value at the time lag of 0 s. As the measured radius of the moved sensor increased, the time lag decreased. The rotational axis of Karman vortex inclined for the trailing edge of rotor blade.

Sign in / Sign up

Export Citation Format

Share Document