Characteristics of Fluctuating Fluid Forces acting on a Circular Cylinder with Cross-Flow Vibrations

2003 ◽  
Vol 2003.43 (0) ◽  
pp. 76-77
Author(s):  
Yukio KONNNO ◽  
Hiroshi SAKAMOTO ◽  
Kazunori TAKAI ◽  
Yoshihiro OBATA
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Fluid Forces

The Hydrodynamic Forces Acting on a Long Flexible Circular Cylinder Responding to VIV

2006 ◽  
Author(s):  
P. W. Bearman ◽  
F. J. Huera Huarte ◽  
J. R. Chaplin
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Element Model ◽  
Transverse Force ◽  
Diameter Ratio ◽  
Mass Ratio ◽  
Force Coefficients ◽  
Fluid Forces ◽  
Maximum Value ◽  
Vibration Prediction

Distributions of the fluid forces acting along a long flexible circular cylinder free to respond in-line and transverse to a stepped current are presented. Forces are calculated using a finite element model of the cylinder with measured responses providing the input. The length to diameter ratio of the model used was 469, the mass ratio was 3 and the Reynolds number could be varied up to maximum value of approximately 2.6 · 104. Fluid force coefficients for two cases are presented: in the first, the dominant modes are the 2nd cross-flow and the 4th in line. For the second case the leading modes are the 7th and 12th respectively. In general, transverse force coefficients and in-line drag coefficients are found to be larger than those measured for short sections of cylinder undergoing free and forced one and two-dimensional motions. It is anticipated that the results will be of value to developers of vortex-induced vibration prediction methods.

TRANSONIC CROSS FLOW (M∞ = 0.8) OVER A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

2012 ◽  
Vol 43 (5) ◽  
pp. 589-613
Author(s):  
Vyacheslav Antonovich Bashkin ◽  
Ivan Vladimirovich Egorov ◽  
Ivan Valeryevich Ezhov ◽  
Sergey Vladimirovich Utyuzhnikov
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

The Numerical Simulation of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinder with High Mass-Ratio

2013 ◽  
Vol 284-287 ◽  
pp. 557-561
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Circular Cylinder ◽  
Drag Force ◽  
Frequency Ratio ◽  
Lift Force ◽  
Degrees Of Freedom ◽  
Cross Flow ◽  
High Mass ◽  
Mass Ratio ◽  
Main Frequency ◽  
Line Amplitude

The two-degrees-of-freedom VIV of the circular cylinder with high mass-ratio is numerically simulated with the software ANSYS/CFX. The VIV characteristic is analyzed in the different conditions (Ur=3, 5, 6, 8, 10). When Ur is 5, 6, 8 and 10, the conclusion which is different from the cylinder with low mass-ratio can be obtained. When Ur is 3, the frequency of in-line VIV is twice of that of cross-flow VIV which is equal to the frequency ratio between drag force and lift force, and the in-line amplitude is much smaller than the cross-flow amplitude. The motion trace is the crescent. When Ur is 5 and 6, the frequency ratio between the drag force and lift force is still 2, but the main frequency of in-line VIV is mainly the same as that of cross-flow VIV and the secondary frequency of in-line VIV is equal to the frequency of the drag force. The in-line amplitude is still very small compared with the cross-flow amplitude. When Ur is up to 8 and 10, the frequency of in-line VIV is the same as the main frequency of cross-flow VIV which is close to the inherent frequency of the cylinder and is different from the frequency of drag force or lift force. But the secondary frequency of cross-flow VIV is equal to the frequency of the lift force. The amplitude ratio of the VIV between in-line and cross-flow direction is about 0.5. When Ur is 5, 6, 8 and 10, the motion trace is mainly the oval.

The Dynamics of Towed Arrays

1989 ◽  
Vol 111 (3) ◽  
pp. 208-213 ◽  
Author(s):  
G. S. Triantafyllou ◽  
C. Chryssostomidis
Keyword(s):  
Iterative Procedure ◽  
Cross Flow ◽  
Low Frequency ◽  
Harmonic Excitation ◽  
Fluid Forces ◽  
Damped System ◽  
Equivalent Linear ◽  
Quadratic Drag ◽  
Linear Damping ◽  
Towed Arrays

A procedure for calculating the response of an array to a harmonic excitation applied at the upstream end is presented. The fluid forces on the array are modeled following the slender-body approximation and the cross-flow principle. An equivalent linear damping is used to replace the quadratic drag due to cross-flow separation. The equivalent linear damping is determined using an iterative procedure. Numerical and asymptotic solutions are derived, and the response of a typical long array is calculated. It is found that, when the separation drag is included, the array exhibits the behavior of an over-damped system, responding only to low-frequency excitations.

Estimation of the Time Delay Associated With Damping Controlled Fluidelastic Instability in a Normal Triangular Tube Array

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Time Delay ◽  
Cross Flow ◽  
Fluid Forces ◽  
Fluidelastic Instability ◽  
Order Of Magnitude ◽  
Sample Frequency ◽  
Pitch Ratio ◽  
Parameterized Model ◽  
Semi Empirical ◽  
Insight Into

Fluidelastic instability (FEI) produces large amplitude self-excited vibrations close to the natural frequency of the structure. For fluidelastic instability caused by the damping controlled mechanism, there is a time delay between tube motion and the resulting fluid forces but magnitude and physical cause of this is unclear. This study measures the time delay between tube motion and the resulting fluid forces in a normal triangular tube array with a pitch ratio of 1.32 subject to air cross-flow. The instrumented cylinder was forced to oscillate in the lift direction at three excitation frequencies for a range of flow velocities. Unsteady surface pressures were monitored with a sample frequency of 2 kHz at the mid plane of the instrumented cylinder. The instantaneous fluid forces were obtained by integrating the surface pressure data. A time delay between the tube motion and resulting fluid forces was obtained. The nondimensionalized time delay was of the same order of magnitude assumed in the semi-empirical quasi-steady model (i.e., τ2 = 0.29 d/U). Although, further work is required to provide a parameterized model of the time delay which can be embedded in a model of damping controlled fluidelastic forces, the data already provides some insight into the physical mechanism responsible.

Vibration Excitation Forces in a Normal Triangular Tube Bundle Subjected to Two-Phase Cross Flow

2011 ◽  
Author(s):  
E. S. Perrot ◽  
N. W. Mureithi ◽  
M. J. Pettigrew ◽  
G. Ricciardi
Keyword(s):  
Tube Bundle ◽  
Cross Flow ◽  
Random Excitation ◽  
Two Phase ◽  
Constant Frequency ◽  
Fluid Forces ◽  
Drag Forces ◽  
Wide Range ◽  
Drag And Lift ◽  
Lift And Drag

This paper presents test results of vibration forces in a normal triangular tube bundle subjected to air-water cross-flow. The dynamic lift and drag forces were measured with strain gage instrumented cylinders. The array has a pitch-to-diameter ratio of 1.5, and the tube diameter is 38 mm. A wide range of void fraction and fluid velocities were tested. The experiments revealed significant forces in both the drag and lift directions. Constant frequency and quasi-periodic fluid forces were found in addition to random excitation. These forces were analyzed and characterized to understand their origins. The forces were found to be dependent on the position of the cylinder within the bundle. The results are compared with those obtained with flexible cylinders in the same tube bundle and to those for a rotated triangular tube bundle. These comparisons reveal the influence of quasi-periodic forces on tube motions.

scholarly journals LAMINAR FLOW PAST AN OSCILLATING CIRCULAR CYLINDER IN CROSS FLOW

2010 ◽  
Vol 18 (3) ◽  
Author(s):  
Pham Anh-Hung ◽  
Lee Chang-Yeol ◽  
Seo Jang-Hoon ◽  
Chun Ho-Hwan ◽  
Kim Hee-Jung ◽  
...  
Keyword(s):  
Laminar Flow ◽  
Circular Cylinder ◽  
Cross Flow ◽  
Flow Past
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