Transverse Vibrations of an Elastically Mounted Cylinder Exposed to an Oscillating Flow

1988 ◽  
Vol 110 (4) ◽  
pp. 387-394 ◽  
Author(s):  
B. M. Sumer ◽  
J. Fredso̸e
Keyword(s):  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Response Patterns ◽  
Test Program ◽  
Current Case ◽  
Number Range ◽  
Response Characteristics ◽  
Vibrational Response ◽  
Transverse Vibrations ◽  
Steady Current

This study reports the results of an experimental work carried out with an elastically mounted rigid cylinder exposed to an oscillating flow. To facilitate comparison, the steady current case is included in the test program as well. The oscillatory flow as well as the steady current conditions are created by the so-called carriage technique. The present study covers the Keulegan-Carpenter number range 5 ≤ KC ≤ 100. The range of the reduced velocity is from 0 to approximately 16 in most of the cases. The tests have been conducted for different combinations of spring stiffness and mass of cylinder. The present results shed considerable light into the understanding of the various vibrational response patterns obtained for different ranges of KC number. The response characteristics of the cylinder have been shown to vary extensively, depending on Keulegan-Carpenter number as well as on the reduced velocity.

Hydrodynamic Forces on Multitube Production Risers Exposed to Currents and Waves

1985 ◽  
Vol 107 (2) ◽  
pp. 226-234 ◽  
Author(s):  
Z. Demirbilek ◽  
T. Halvorsen
Keyword(s):  
Large Scale ◽  
Oscillatory Flow ◽  
Companion Paper ◽  
Hydrodynamic Forces ◽  
Primary Objective ◽  
Oscillating Flow ◽  
Oil Companies ◽  
Steady Current ◽  
Pertinent Data ◽  
Analysis And Synthesis

This paper presents the experimental results of a joint industry riser test program. Over a five-year period, an extensive experimental investigation of hydrodynamic loads acting on various production risers was carried out. The program included the laboratory testing of many multitube riser configurations as well as a single cylinder. Several major oil companies sponsored the project. The tests were made with rather large-scale models which were: 1) held stationary in steady current, 2) moved at constant speed or constant acceleration through a quiescent fluid or through a moving fluid, and 3) held stationary in oscillating flow or in steady current superimposed on oscillating flow. The primary objective of this investigation was to establish an accurate measurement of the hydrodynamic forces on bundle-type risers. The findings from this study will be presented in two papers. In the first, we shall present the hydrodynamic force coefficients for some marine risers consisting of one or more cylinders interacting either only with currents or oscillatory flow separately. In a companion paper, the pertinent data for the joint presence of the oscillatory flow and currents will be discussed. Among the results outlined here are the drag, inertia, and lift coefficients for various composite risers as a function of the Reynolds and Keulegan-Carpenter numbers. An analysis and synthesis of the test data are also presented.

Hydrodynamic Loading on Macro-Roughened Cylinders of Various Aspect Ratios

1989 ◽  
Vol 111 (3) ◽  
pp. 214-222 ◽  
Author(s):  
A. Theophanatos ◽  
J. Wolfram
Keyword(s):  
Offshore Structures ◽  
Water Tank ◽  
Fluid Loading ◽  
Test Rig ◽  
Test Program ◽  
Number Range ◽  
Marine Fouling ◽  
Aspect Ratios ◽  
The Uk ◽  
Regular Arrays

This paper describes experiments which comprise part of the UK joint SERC/industry-sponsored program on fluid loading. The experiments have been undertaken in a novel test rig which accelerates a cylinder from rest to a constant velocity in a still water tank and cover the Reynolds number range 105 to 106. Results are presented for 30 cylinders ranging in diameter from 150 mm to 400 mm. The test program comprised: (a) cylinders with different distributions of marine growth (mussels and kelp) and artificial roughness at low surface cover; (b) fully sand/gravel-roughened cylinders with aspect ratios (L/D) from 3.75 to 10 and relative roughness (k/D) up to 0.025; (c) cylinders covered in regular arrays of pyramids at (k/D) up to 0.1. Based on the results, some tentative conclusions are drawn about the estimation of the effect of marine fouling on the fluid loading of offshore structures.

On Vessel Motion Induced Vortex-Induced Vibrations of a Steel Lazy Wave Riser

2021 ◽  
Author(s):  
Decao Yin
Keyword(s):  
Vortex Shedding ◽  
Time Domain ◽  
Oscillatory Flow ◽  
Domain Model ◽  
Time Varying ◽  
Structure Interaction ◽  
Response Characteristics ◽  
Vortex Induced Vibrations ◽  
The Time Domain ◽  
Vessel Motion

Abstract Deepwater steel lazy wave risers (SLWR) subject to vessel motion will be exposed to time-varying oscillatory flow, vortices could be generated and the cyclic vortex shedding force causes the structure vibrate, such fluid-structure interaction is called vortex-induced vibrations (VIV). To investigate VIV on a riser with non-linear structures under vessel motion and oscillatory flows, time domain approaches are needed. In this study, a time-domain approach is used to simulate a full-scale SLWR. Two cases with simplified riser top motions are simulated numerically. By using default input parameters to the time domain approach, the key oscillatory flow induced VIV response characteristics such as response frequency, curvature and displacements are examined and discussed. More accurate VIV prediction could be achieved by using realistic hydrodynamic inputs into the time domain model.

Oscillatory Flow of a Magnetic Fluid in a Pipe at Low Frequency Range Under a Magnetic Field: Phase Difference of Pressure

2003 ◽  
Author(s):  
Kunio Shimada ◽  
Shigemitsu Shuchi ◽  
Shinichi Kamiyama
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Phase Difference ◽  
Mass Concentration ◽  
Oscillatory Flow ◽  
Low Frequency ◽  
Nonuniform Distribution ◽  
Straight Pipe ◽  
Number Range ◽  
Steady Magnetic Field

We made on numerical analysis of phase difference between pressure along the pipe axis and given oscillatory flow velocity in an straight pipe under a nonuniform steady magnetic field. In the analysis, a few cases under the assumption of numerical condition were conducted on: the first is taking into account the least compressibility of the fluid with using the obtained experimental data of the bulk modulus, the second taking into account the nonuniform distribution of mass concentration of particles, and the thrid taking into account the aggregation with the number of aggregated particles proposing as a prorate spheroid. By considering the three effects of the least compressibility and the nonuniform distribution of mass concentration, the aggregation as a prorate spheroid, the phase difference varies quantitatively at the lowest Womersley number range. And then, the numerical results were compared with the experimental data.

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.

Liquid-Vapor Oscillating Flow and Heat Transfer in a U-Shaped Minichannel With Internal Wick Structure

2009 ◽  
Author(s):  
Jiajun Xu ◽  
Yuwen Zhang ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Transfer Coefficients ◽  
Oscillating Heat Pipe ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Flow And Heat Transfer ◽  
Wick Structure ◽  
Liquid Vapor

Liquid-vapor oscillating flow and heat transfer in a vertically placed oscillating heat pipe (OHP) with a sintered particle wick structure inside are analyzed in this paper. The evaporation and condensation heat transfer coefficients are obtained by solving the microfilm evaporation and condensation on the sintered particles. The sensible heat transfer between the liquid slug and the channel wall are obtained by analytical solution or empirical correlations, depending on whether the liquid flow is laminar or turbulent. The effects of the maximum evaporation and condensation angles on the oscillatory flow, as well as sensible and latent heat transfer are analyzed.

Three-dimensional vortex dynamics in oscillatory flow separation

2011 ◽  
Vol 674 ◽  
pp. 408-432 ◽  
Author(s):  
MIGUEL CANALS ◽  
GENO PAWLAK
Keyword(s):  
Time Scale ◽  
Oscillatory Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Outer Region ◽  
Vortex Pair ◽  
Propagation Distance ◽  
Oscillation Period ◽  
Number Range ◽  
Elliptical Instability

The dynamics of coherent columnar vortices and their interactions in an oscillatory flow past an obstacle are examined experimentally. The main focus is on the low Keulegan–Carpenter number range (0.2 < KC < 2), where KC is the ratio between the fluid particle excursion during half an oscillation cycle and the obstacle size, and for moderate Reynolds numbers (700 < Rev < 7500). For this parameter range, a periodic unidirectional vortex pair ejection regime is observed, in which the direction of vortex propagation is set by the initial conditions of the oscillations. These vortex pairs provide a direct mechanism for the transfer of momentum and enstrophy to the outer region of rough oscillating boundary layers. Vortices are observed to be short-lived relative to the oscillation time scale, which limits their propagation distance from the boundary. The instability mechanisms leading to vortex decay are elucidated via flow visualizations and digital particle image velocimetry (DPIV). Dye visualizations reveal complex three-dimensional vortex interactions resulting in rapid vortex destruction. These visualizations suggest that one of the instabilities affecting the spanwise vortices is an elliptical instability of the strained vortex cores. This is supported by DPIV measurements which identify the spatial structure of the perturbations associated with the elliptical instability in the divergence field. We also identify regions in the periphery of the vortex cores which are unstable to the centrifugal instability. Vortex longevity is quantified via a vortex decay time scale, and the results indicate that vortex pair lifetimes are of the order of an oscillation period T.

Planar Oscillatory Flow Forces at High Reynolds Numbers

1993 ◽  
Vol 115 (1) ◽  
pp. 31-39 ◽  
Author(s):  
J. R. Chaplin
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Number Range ◽  
High Reynolds Numbers ◽  
Reynolds Number Range ◽  
Fine Surface ◽  
High Reynolds

Measurements of pressures around a circular cylinder with fine surface roughness in planar oscillatory flow reveal considerable changes in drag and inertia coefficients over the Reynolds number range 2.5 × 105 to 7.5 × 105, and at Keulegan-Carpenter numbers between 5 and 25. In most respects, these results are shown to be compatible with previous measurements in planar oscillatory flow, and with previous measurements in which the same 0.5-m-dia cylinder was tested in waves.

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