Vortex Excited Oscillations of Yawed Circular Cylinders

1977 ◽  
Vol 99 (3) ◽  
pp. 495-501 ◽  
Author(s):  
R. King
Keyword(s):  
Reynolds Number ◽  
Theoretical Work ◽  
Circular Cylinders ◽  
Stability Criteria ◽  
Local Flow ◽  
Braced Frame ◽  
Flowing Fluid ◽  
Number Range ◽  
Drag Forces ◽  
The Stability

Yawed cylinders are cylinders inclined forward or backwards in the plane of the flowing fluid. They are used in many practical situations such as braced frame members and raked marine piles. This paper describes an examination of three aspects of the yawed cylinder-fluid interactions over a range of yaw angles ±45° from the vertical for the Reynolds number range 2,000 < Re < 20,000. viz. 1. Establishment of the stability criteria of vortex-excited oscillations. 2. Measurement of ‘steady’ drag forces and equivalent drag coefficients. 3. Visualization of the local flow over stationary and oscillating cylinder. After a brief review of previous experimental and theoretical work, the results of the three items listed above are presented and discussed. Vortex-excited oscillations were recorded in the in-line and crossflow directions throughout the range of yaw angles and the results of items 2, 3 were used to justify the forms of the stability criteria proposed for these oscillations.

scholarly journals Effect of Rotational Speed on the Stability of Two Rotating Side-by-side Circular Cylinders at Low Reynolds Number

2018 ◽  
Vol 27 (2) ◽  
pp. 125-134
Author(s):  
Huashu Dou ◽  
Shuo Zhang ◽  
Hui Yang ◽  
Toshiaki Setoguchi ◽  
Yoichi Kinoue
Keyword(s):  
Reynolds Number ◽  
Rotational Speed ◽  
Low Reynolds Number ◽  
Circular Cylinders ◽  
Low Reynolds ◽  
The Stability

Stability of spiral flow between concentric circular cylinders at low axial Reynolds number

1965 ◽  
Vol 21 (4) ◽  
pp. 635-640 ◽  
Author(s):  
Subhendu K. Datta
Keyword(s):  
Reynolds Number ◽  
Perturbation Theory ◽  
Viscous Liquid ◽  
Axial Flow ◽  
Circular Cylinders ◽  
Rotating Cylinders ◽  
Spiral Flow ◽  
The Stability

The stability of a viscous liquid between two concentric rotating cylinders with an axial flow has been investigated. Attention has been confined to the case when the cylinders are rotating in the same direction, the gap between the cylinders is small and the axial flow is small. A perturbation theory valid in the limit when the axial Reynolds number R → 0 has been developed and corrections have been obtained for Chandrasekhar's earlier results.

Study on In-Flow Vibration of Cylinder Arrays Caused by Cross Flow

2011 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Keisuke Nishimura ◽  
Yoshiaki Fujita ◽  
Chihiro Kohara
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Thin Plates ◽  
Streamwise Direction ◽  
Number Range ◽  
Direction Transverse ◽  
Drag Forces ◽  
Cylinder Arrays ◽  
Reynolds Number Range

The authors have studied the in-flow vibration phenomena of cylinder arrays caused by cross-flow in the low Reynolds number range around Re=800. This Reynolds number range has been studied because it is the range where symmetric vortex shedding occurs. This report is our first trial to study the in-line fluidelastic vibration of cylinder arrays. In initial tests, the flow velocity was increased up to the maximum achievable level by the test equipment. However, it was found that the array’s cantilever tube supports resulted in large static tube deflections due to static drag forces. The cylinder array tube supports have therefore been replaced by thin plates supported at both ends. The cylinders are set to be flexible both in the streamwise direction and the direction transverse to the flow. The obtained results of these two patterns are also compared with previous cantilevered data. The origin of the observed vibrations whether a self-induced mechanism or vortex shedding is discussed in detail.

Effect of Reynolds Number on Local Scour Around a Monopile in Steady Current

2019 ◽  
Author(s):  
Xiaofan Lou ◽  
Kaibing Zhang ◽  
Zhenhong Chen
Keyword(s):  
Reynolds Number ◽  
Time Scale ◽  
Time History ◽  
Local Scour ◽  
Circular Cylinders ◽  
Scour Depth ◽  
Clear Water ◽  
Number Range ◽  
Steady Current ◽  
Equilibrium Scour Depth

Abstract The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

The effects of surface roughness on the flow past circular cylinders at high Reynolds numbers

1982 ◽  
Vol 123 ◽  
pp. 363-378 ◽  
Author(s):  
Y. Nakamura ◽  
Y. Tomonari
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
High Reynolds Number ◽  
Circular Cylinders ◽  
Similarity Parameter ◽  
Number Range ◽  
Pressure Distributions ◽  
Mean Pressure ◽  
Supercritical Range ◽  
High Reynolds

Measurements of’ the mean-pressure distribution and the Strouhal number on a smooth circular cylinder, circular cylinders with distributed roughness, and circular cylinders with narrow roughness strips were made over a Reynolds-number range 4.0 × l04 to 1.7 × l06 in a uniform flow. A successful high-Reynolds-number (trans- critical) simulation for a smooth circular cylinder is obtained using a smooth circular cylinder with roughness strips. High-Reynolds-number simulation can only be obtained by roughness strips and not by distributed roughness. A similarity parameter correlating the pressure distributions on circular cylinders with distributed roughness in the supercritical range is presented. The same parameter can also be applicable to the drag coefficients of spheres with distributed roughness.

The lift and drag forces on a circular cylinder in a flowing fluid

1964 ◽  
Vol 277 (1368) ◽  
pp. 32-50 ◽  
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Drag Force ◽  
Central Axis ◽  
Flowing Fluid ◽  
Drag Forces ◽  
Lift And Drag

Apparatus is described for measuring directly fluctuating lift and drag forces and steady mean drag force. These forces are exerted upon a cylinder placed so that its central axis is perpendicular to the direction of flow of water in a channel. Results are given for the stationary cylinder for the range of Reynolds number 3600 to 11 000.

Local Flow and Heat Transfer Behavior in Convex-Louver Fin Arrays

1999 ◽  
Vol 121 (1) ◽  
pp. 136-141 ◽  
Author(s):  
N. C. DeJong ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Shear Layer ◽  
Local Flow ◽  
Number Range ◽  
Flow And Heat Transfer ◽  
Transfer Behavior ◽  
Strip Geometry

Local and surface-averaged measurements of convection coefficients and core pressure-drop data are provided for an array of convex-louver fins. For a Reynolds number range from 200 to 5400, these data are complemented with a flow visualization study and contrasted with new measurements from a similar offset-strip geometry. The results clarify the effects of boundary layer restarting, shear-layer unsteadiness, spanwise vortices, and separation, reattachment, and recirculation on heat transfer in the convex-louver geometry.

A note on vortex streets behind circular cylinders at low Reynolds numbers

1971 ◽  
Vol 45 (1) ◽  
pp. 203-208 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Current State ◽  
Reynolds Number Range ◽  
Vortex Streets ◽  
Low Reynolds

A discussion is given of the current state of knowledge of vortex streets behind circular cylinders in the Reynolds number range 50 to 160. This was prompted by Gaster's (1969) report that he could not find the transition at a Reynolds number of about 90 observed by Tritton (1959) and Berger (1964a). A further brief experiment confirming the existence of the transition is described Reasons for rejecting Gaster's interpretation are advanced. Possible (mutually alternative) explanations of the discrepant observations are suggested.

Pulse dynamics in a power-law falling film

2014 ◽  
Vol 747 ◽  
pp. 460-480 ◽  
Author(s):  
M. Pradas ◽  
D. Tseluiko ◽  
C. Ruyer-Quil ◽  
S. Kalliadasis
Keyword(s):  
Reynolds Number ◽  
Power Law ◽  
Thin Liquid Film ◽  
Small Strain ◽  
Shear Thinning ◽  
Final State ◽  
Local Flow ◽  
Stability Dynamics ◽  
The Stability ◽  
Low Dimensional

AbstractWe examine the stability, dynamics and interactions of solitary waves in a two-dimensional vertically falling thin liquid film that exhibits shear-thinning effects. We use a low-dimensional two-field model that describes the evolution of both the local flow rate and the film thickness and is consistent up to second-order terms in the long-wave expansion. The shear-thinning behaviour is modelled via a power-law formulation with a Newtonian plateau in the limit of small strain rates. Our results show the emergence of a hysteresis behaviour as the control parameter (the Reynolds number) is increased which is directly related to the shear-thinning character of the liquid and can be quantified with both linear analysis arguments and a physical interpretation. We also study pulse interactions, observing that two pulses may attract or repel each other either monotonically or in an oscillatory manner. In large domains we find that for a given Reynolds number the final state depends on the initial condition, a consequence of the presence of multiple solutions.

Global frequency selection in the observed time-mean wakes of circular cylinders

2008 ◽  
Vol 601 ◽  
pp. 425-441 ◽  
Author(s):  
MOSES KHOR ◽  
JOHN SHERIDAN ◽  
MARK C. THOMPSON ◽  
KERRY HOURIGAN
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Linear Instability ◽  
Circular Cylinders ◽  
Near Wake ◽  
Mean Velocity ◽  
Number Range ◽  
Wake Instability ◽  
Karman Vortex

Observations have been made of the time-mean velocity profile at midspan in the near-wake of circular cylinders at moderate Reynolds numbers between 600 and 4600, well beyond the Reynolds number of approximately 200 at which the wake becomes three-dimensional. The measured profiles are found to be represented quite accurately by a family of function profiles with known linear instability characteristics. The complex instability frequency is then determined as a function of wake position, using the function profiles. In general, the near wake undergoes a transition from convective to absolute instability; the distance downstream to the point of transition is found to increase over the Reynolds number range investigated. The emergence of a significant region of convective instability is consistent with the known appearance of Bloor–Gerrard vortices. The selected frequency of the wake instability is determined by the saddle-point criterion; the Strouhal numbers for Bénard–von Kármán vortex shedding are found to compare well with the values in the literature.

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