Vortex-Excited Cross-Flow Vibrations of a Single Cylindrical Tube

1980 ◽  
Vol 102 (2) ◽  
pp. 158-166 ◽  
Author(s):  
O. M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Cylindrical Tube ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Resonant Response ◽  
Single Tube ◽  
Fluid Forces ◽  
Dynamic Forces

The cross-flow vibrations of a single tube are considered in this paper, for incident flows of air and water. Recent experimental measurements of the resonant response of and fluid dynamic forces on circular cylinders as a result of vortex shedding at subcritical Reynolds numbers are presented, and different approaches to measuring and characterizing the fluid forces are compared. Based upon these experiments, a mathematical model with which to describe the flow-induced excitation and reaction (damping) forces on a vibrating tube has been developed and is presented here. These results are applicable in general not only to the resonant, vortex-excited vibrations of flexibly mounted rigid tubes, but also to a flexible tube in air, water and other similar fluids.

High-Resolution Numerical Simulation of Low Reynolds Number Incompressible Flow About Two Cylinders in Tandem

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Sintu Singha ◽  
K. P. Sinhamahapatra
Keyword(s):  
Reynolds Number ◽  
Incompressible Flows ◽  
Fluid Dynamic ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Dynamic Forces ◽  
Low Reynolds ◽  
Volume Method ◽  
Global Parameters

Low Reynolds number steady and unsteady incompressible flows over two circular cylinders in tandem are numerically simulated for a range of Reynolds numbers with varying gap size. The governing equations are solved on an unstructured collocated mesh using a second-order implicit finite volume method. The effects of the gap and Reynolds number on the vortex structure of the wake and on the fluid dynamic forces acting on the cylinders are reported and discussed. Both the parameters have significant influence on the flow field. An attempt is made to unify their influence on some global parameters.

Interference Between Two Stationary or Elastically Supported Rigid Circular Cylinders of Unequal Diameters in Tandem and Staggered Arrangements

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Shan Huang ◽  
Andy Sworn
Keyword(s):  
Drag Reduction ◽  
Vortex Shedding ◽  
Damping Ratio ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Test Results ◽  
Damping Parameter ◽  
Frequency Components ◽  
Elastically Supported

Analysis of model test results was carried out to investigate the hydrodynamic interaction between pairs of fixed or elastically supported rigid cylinders of dissimilar diameters in a water flume. The two cylinders are placed with one situated in the wake of the other. The spacing between the cylinders ranges from 1 to 15 times the larger cylinder diameter. The Reynolds numbers are within the subcritical range. For the vibrating cylinders which are free to oscillate in both the in-line and the cross-flow directions, the reduced velocity ranges from 1 to 13 and the low damping ratio of the test setup at 0.006 gives a combined mass-damping parameter of 0.02. For the fixed cylinders, the downstream cylinder experiences a drag reduction and it was found that this drag reduction also depends upon the diameter ratio. The lift on the fixed downstream cylinder has the frequency components derived from the upstream cylinder's vortex shedding as well as from its own vortex shedding, and the relative importance of the two sources is influenced by the spacing between the two cylinders. This is reflected in the downstream cylinder's vortex induced vibration (VIV) response which appears to be dependent upon the actual reduced velocities of both the cylinders.

Circular Cylinder Exposed to Cross Flow Fluid Forces – Parameters of Influence – Limits of Numerical Models

2003 ◽  
Author(s):  
Christoph Reichel ◽  
Klaus Strohmeier
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Models ◽  
Lift Coefficient ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Rigid Cylinder ◽  
Fluid Forces ◽  
Wide Range ◽  
Dynamics Simulations

In many technical fields, e.g. heat exchangers, circular cylinders are involved in Fluid Structure Interaction (FSI) problems. Therefore correct frequency and magnitude of fluid forces, respectively Strouhal number, drag and lift coefficient are needed. If fluid forces are evaluated with Computational Fluid Dynamics (CFD), mostly flow around a rigid cylinder is used to verify model and numerical methods. Unfortunately experimental as well as numerical results show great variation, making verification and testing of models difficult. Reynolds number is regarded as main influencing parameter for a rigid cylinder in cross flow. Most of experimental deviations can be related to other parameters, which differ from experiment to experiment. In this paper such parameters are specified and it is shown, that a closer look is needed, if one really wants to verify a model. Besides experimental results, which can be found in literature, some parameters are investigated by numerical simulation. Like experiments CFD (Computational Fluid Dynamics) simulations show a huge bandwidth of results, even when the same turbulence model is used. Flow around cylinders separates over a wide range of Reynolds numbers. It will be demonstrated that, using CFD, large deviations in fluid forces can often be related to miscalculation of the point of separation.

Vortex Shedding from Smooth and Roughened Cylinders in Cross-Flow near a Plane Surface

1979 ◽  
Vol 30 (1) ◽  
pp. 305-321 ◽  
Author(s):  
G. Buresti ◽  
A. Lanciotti
Keyword(s):  
Vortex Shedding ◽  
Plane Surface ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Cylinder Surface ◽  
Hot Wire ◽  
Cylinder Axis ◽  
Supercritical Regime ◽  
Subcritical Regime ◽  
Smooth Cylinder

SummaryThe characteristics of the flow field around a circular cylinder in cross-flow placed at various distances from a plane, parallel both to the flow and to the cylinder axis, were analysed using a hot wire anemometer. Experiments were performed in a wind tunnel with Reynolds numbers ranging from 0.85×105 to 3×105. The spectra of the hot wire signals were obtained using a Fast Fourier Transform technique programmed on a PDP 11/40 computer. As regards a smooth cylinder, the main features of the vortex shedding mechanism in the subcritical regime remained unaltered for distances from the plane greater than approximately 0.4 diameters; in particular the Strouhal frequency did not show any significant variation relative to the typical value for an isolated cylinder. As for lower values of the distance from the plane, the regular vortex shedding disappeared and the hot wire spectra showed typical turbulent features. The possibility of obtaining supercritical conditions by roughening the cylinder surface was confirmed together with the importance of the Reynolds number based on the typical roughness size, Rk, in the evaluation of the flow regime around the cylinder. In the case of roughened cylinders, and with values of Rk below-350, the regular vortex shedding disappeared at a distance from the plane smaller than 0.3 diameters. This fact suggests that, at least in part of the supercritical regime, the influence of the plane can be smaller than in the subcritical regime.

Flow-Induced Vibration of Tube Arrays With Various Pitch-to-Diameter Ratios

1982 ◽  
Vol 104 (3) ◽  
pp. 168-174 ◽  
Author(s):  
H. Tanaka ◽  
S. Takahara ◽  
K. Ohta
Keyword(s):  
Fluid Dynamic ◽  
Cross Flow ◽  
Diameter Ratio ◽  
Flow Induced Vibration ◽  
Threshold Velocity ◽  
Unsteady Forces ◽  
Practical Applications ◽  
Tube Arrays ◽  
Dynamic Forces ◽  
Unsteady Fluid

Tube arrays in cross flow start to vibrate abruptly when the flow reaches at a certain velocity. The threshold flow velocity depends upon the geometrical arrangement of tubes. It is very important for practical applications to understand the relations between the threshold velocity and pitch-to-diameter ratio of tube array. Unsteady fluid dynamic forces on a tube array with a pitch-to-diameter ratio of 2.0 were clarified experimentally and the characteristics of the threshold velocity were revealed by calculating the velocity with the unsteady forces. By comparing the threshold velocities of tube arrays of pitch-to-diameter ratio of 2.0 and 1.33, the characteristics of threshold velocity with respect to pitch-to-diameter ratio were clarified.

Two-dimensional numerical study of vortex shedding regimes of oscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers

2014 ◽  
Vol 751 ◽  
pp. 1-37 ◽  
Author(s):  
Ming Zhao ◽  
Liang Cheng
Keyword(s):  
Vortex Shedding ◽  
Oscillatory Flow ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
The Other ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Low Reynolds Numbers ◽  
Single Cylinder ◽  
Gap Ratio

AbstractOscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers is simulated numerically by solving the two-dimensional Navier–Stokes (NS) equations using a finite-element method (FEM). The aim of this study is to identify the flow regimes of the two-cylinder system at different gap arrangements and Keulegan–Carpenter numbers (KC). Simulations are conducted at seven gap ratios $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}G$ ($G=L/D$ where $L$ is the cylinder-to-cylinder gap and $D$ the diameter of a cylinder) of 0.5, 1, 1.5, 2, 3, 4 and 5 and KC ranging from 1 to 12 with an interval of 0.25. The flow regimes that have been identified for oscillatory flow around a single cylinder are also observed in the two-cylinder system but with different flow patterns due to the interactions between the two cylinders. In the side-by-side arrangement, the vortex shedding from the gap between the two cylinders dominates when the gap ratio is small, resulting in the gap vortex shedding (GVS) regime, which is different from any of the flow regimes identified for a single cylinder. For intermediate gap ratios of 1.5 and 2 in the side-by-side arrangement, the vortex shedding mode from one side of each cylinder is not necessarily the same as that from the other side, forming a so-called combined flow regime. When the gap ratio between the two cylinders is sufficiently large, the vortex shedding from each cylinder is similar to that of a single cylinder. In the tandem arrangement, when the gap between the two cylinders is very small, the flow regimes are similar to that of a single cylinder. For large gap ratios in the tandem arrangement, the vortex shedding flows from the gap side of the two cylinders interact and those from the outer sides of the cylinders are less affected by the existence of the other cylinder and similar to that of a single cylinder. Strong interaction between the vortex shedding flows from the two cylinders makes the flow very irregular at large KC values for both side-by-side and tandem arrangements.

Model Test on Drag of Cylinders With Helical Grooves at High Reynolds Numbers

2010 ◽  
Author(s):  
Shan Huang ◽  
Neil Kitney
Keyword(s):  
Model Test ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Tank Model ◽  
Towing Tank ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Helical Grooves ◽  
Four Cylinders

Towing tank model tests at high Reynolds numbers, up to 1.1×106, were carried out in order to investigate the effects of the triple-starting helical grooves on drag reduction of smooth and rough circular cylinders in uniform cross flow. In total, four cylinders were tested including smooth and rough cylinders with and without helical grooves.

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