Wake-induced galloping of two interfering circular cylinders

1984 ◽  
Vol 146 ◽  
pp. 383-415 ◽  
Author(s):  
A. Bokaian ◽  
F. Geoola
Keyword(s):  
Relative Position ◽  
Free Stream ◽  
Dynamic Instability ◽  
Fluid Dynamic ◽  
Continuous Functions ◽  
Circular Cylinders ◽  
Static Tests ◽  
Free Stream Turbulence ◽  
Drag Forces ◽  
The Stability

Measurements are presented of fluid-dynamic instability of a smooth circular cylinder, free to oscillate laterally against linear springs in the wake from an identical stationary neighbouring body. The observations also encompassed determination of static forces on the downstream cylinder as functions of relative position of the cylinder pair. Most of the experiments were performed under two conditions of free-stream turbulence. Static tests indicated that both the drag coefficient and the Strouhal number of the downstream body are continuous functions of its relative position. The drag forces were found to be negative at small gaps. It was observed that the transverse extent of the force field increases with increasing streamwise gap.In the dynamic experiments, depending on the cylinders’ separation and structural damping, the cylinder exhibited a vortex-resonance, or a galloping, or a combined vortex-resonance and galloping, or a separated vortex-resonance and galloping. Whilst the characteristics of wake-excited motion were found to be essentially unaffected by a limited change in free-stream turbulence intensity, the galloping amplitudes were observed to be sensitive to the cylinders’ aspect ratio. An increase in the stability parameter caused significant effects on the cylinder response in amplitude domain. Wake observations behind the oscillating body indicated that in vortex lock-in the frequency of vortex-shedding locked to vibration frequency, but during small-amplitude galloping motion the shedding frequency behaved as if the cylinder was stationary.

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 Turbulence Intensity, Length Scale, and Heat Transfer Around Stagnation Line of Cylinder and Model Blade

1999 ◽  
Author(s):  
V. P. Maslov ◽  
B. I. Mineev ◽  
K. N. Pichkov ◽  
A. N. Secundov ◽  
A. N. Vorobiev ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Turbulence Models ◽  
Leading Edge ◽  
Circular Cylinders ◽  
Length Scale ◽  
Stagnation Line ◽  
Free Stream Turbulence ◽  
Wide Range

A hot-wire technique was used to measure turbulence characteristics in the vicinity of the stagnation line of circular cylinders and a turbine blade model (a chord length of 1 metre). Heat transfer intensity at the stagnation line of the cylinders was also measured by on-surface probes. The experiments were carried out in a wide range of the Reynolds number based on the blade leading edge/cylinder diameter, D (Re = 2.103–2.106) and integral length scale of free-stream turbulence, Le (Le = 0.1–10D) at two values of free stream turbulence intensity, Tu (Tu = 0.02 and 0.10). Along with the experimental data results of the 2D RANS computations are presented of the flow and heat transfer at the circular cylinder with the use of two turbulence models: a two-equation, k-ω SST, model of Menter, and a new two-equation, ν1-L, model developed in the course of the present study.

Local Force Measurements on Finite-Span Cylinders in a Cross-Flow

1987 ◽  
Vol 109 (2) ◽  
pp. 136-143 ◽  
Author(s):  
V. K. Sin ◽  
Ronald M. C. So
Keyword(s):  
Free Stream ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Force Measurements ◽  
Unsteady Forces ◽  
Free Stream Turbulence ◽  
Finite Span ◽  
Present Technique ◽  
Unsteady Force

A technique employing a three-axis piezoelectric load cell is developed to measure local unsteady forces induced on cylinders placed in a cross flow. Verification of the technique is carried out with a two-dimensional circular cylinder. All measurements are made at a Reynolds number of ∼4.8 × 104 and a free-stream turbulence of ∼1.5 percent. The local two-dimensional unsteady lift measurement is found to be in excellent agreement with spanwise-averaged data reported in the literature, thereby validating the feasibility of the present technique. Steady and unsteady force measurements on finite-span circular cylinders are reported and compared with available data in the literature.

Experimental study of the stability of heated laminar boundary layers in water

1977 ◽  
Vol 83 (2) ◽  
pp. 225-247 ◽  
Author(s):  
A. J. Strazisar ◽  
E. Reshotko ◽  
J. M. Prahl
Keyword(s):  
Free Stream ◽  
Parallel Flow ◽  
Neutral Stability ◽  
Free Stream Turbulence ◽  
Laminar Boundary Layers ◽  
Wall Heating ◽  
The Stability ◽  
Energy Equations ◽  
Hot Film ◽  
Disturbance Growth

Linear sinusoidal disturbances are introduced into the boundary layer over a heated flat plate of uniform surface temperature using a vibrating ribbon. The experiment is performed in a low turbulence water tunnel with free-stream turbulence intensities of 0[sdot ]1–0[sdot ]2%. Measurements are made using temperature-compensated hot-film anemometry. Neutral-stability characteristics obtained for the unheated case agree favourably with previous results obtained both in water and in air. Neutral-stability and spatial disturbance-growth-rate characteristics measured for wall temperatures up to 8°F above the free-stream temperature verify trends established by parallel-flow solutions of the disturbance momentum and energy equations. Disturbance growth rates and the band of amplified disturbance frequencies both decrease as wall heating is increased. The experimentally observed increase in the minimum critical Reynolds number Recmin with increased wall heating agrees with the trend predicted by theory. However, effects of non-parallel flow act to reduce the measured values of Recmin by about 120 units compared with predicted parallel-flow values independent of the level of wall heating.

Current-Induced Fluidelastic Instabilities of a Multi-Tube Flexible Riser: Theoretical Results and Comparison With Experiments

1993 ◽  
Vol 115 (4) ◽  
pp. 206-212 ◽  
Author(s):  
S. J. Price ◽  
M. P. Pai¨doussis ◽  
A. M. Al-Jabir
Keyword(s):  
Free Stream ◽  
Cross Flow ◽  
Quantitative Agreement ◽  
Circular Cylinders ◽  
Flexible Riser ◽  
Tunnel Model ◽  
Flow Induced Vibrations ◽  
Static Fluid ◽  
The Stability ◽  
Theoretical Results

Previous experiments on a five-riser cluster in steady cross-flow have indicated that for certain orientations of the cluster the peripheral, or wing, risers can undergo violent flow-induced vibrations. It was shown that these vibrations were not due to vortex shedding; furthermore, it was suggested that they are due to a classical self-excited fluidelastic instability. In the present paper, a previously developed quasi-steady fluidelastic stability analysis for a group of circular cylinders in steady crossflow is modified to enable the stability of a flexible riser in a five-riser bundle to be analyzed. As input to the theoretical model, the static fluid force coefficients on a peripheral riser, and the manner in which they vary with displacement, are required. These were measured for a number of orientations of the cluster with respect to the free-stream current, using a wind tunnel model. Using this data in the analysis, the stability of a five-riser cluster was investigated. Instability is predicted to occur for the same orientations of the riser as obtained from the experimental results; however, the quantitative agreement between experimental and theoretical critical flow velocities for instability to occur is not as good. Theory also predicts the system to be stable for those orientations where no instability was obtained experimentally.

Instability Mechanisms and Stability Criteria of a Group of Circular Cylinders Subjected to Cross-Flow. Part I: Theory

1983 ◽  
Vol 105 (1) ◽  
pp. 51-58 ◽  
Author(s):  
S. S. Chen
Keyword(s):  
Dynamic Instability ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Stability Criteria ◽  
Critical Flow Velocity ◽  
Closed Form Solutions ◽  
Fluid Damping ◽  
Functional Forms ◽  
Flow Part ◽  
The Stability

A mathematical model is presented for a group of circular cylinders subject to cross-flow. It is found that there are two basic dynamic instability mechanisms: instability controlled by fluid damping and instability controlled by fluidelastic force. Approximate closed form solutions of the critical flow velocity for the two mechanisms are obtained based on constrained-mode analyses. The model has identified the key parameters in the stability criteria and their functional forms and resolved the controversy associated with the empirical stability criteria.

ESTIMATION OF THE EFFECT OF FREE-STREAM TURBULENCE AND SOLID PARTICLES ON THE LAMINAR-TURBULENT TRANSITION AT HYPERSONIC SPEEDS

2016 ◽  
Vol 47 (1) ◽  
pp. 15-28 ◽  
Author(s):  
Mikhail Aleksandrovich Pugach ◽  
Alexander Aleksandrovich Ryzhov ◽  
Alexander Vitalievich Fedorov
Keyword(s):  
Free Stream ◽  
Solid Particles ◽  
Free Stream Turbulence ◽  
Turbulent Transition ◽  
Hypersonic Speeds ◽  
Laminar Turbulent Transition
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