scholarly journals Research on Separated Flow around A Submerged Horizontal Cylinder in Water Waves and Currents

1990 ◽  
Vol 1990 (168) ◽  
pp. 193-202
Author(s):  
Hisaaki Maeda ◽  
Koichi Masuda ◽  
Fumio Maruyama ◽  
Yuka Kitakouji
Keyword(s):  
Water Waves ◽  
Separated Flow ◽  
Horizontal Cylinder ◽  
Waves And Currents

Dispersal and floating ability of dimorphic fruit segments of Cakile edentula var. lacustris

1981 ◽  
Vol 59 (12) ◽  
pp. 2595-2602 ◽  
Author(s):  
Anita M. Payne ◽  
M. A. Maun
Keyword(s):  
Water Waves ◽  
Sandy Beaches ◽  
Georgian Bay ◽  
New Locations ◽  
Waves And Currents ◽  
Cakile Edentula ◽  
Strong Winds

Cakile edentula (Bigel) Hook var. lacustris occurs abundantly along sandy beaches of Lakes Huron, Erie and Ontario. Until now the species had not been reported to occur along Georgian Bay but we located one population at Deanlea Beach. The deciduous upper fruit segments disperse long distances by water waves and currents and short distances by rolling caused by strong winds. The lower fruit segments usually remain attached to the parents which may be uprooted by high waves and then transported as tumble weeds to new locations. The floatation experiment showed that the agitation of jars containing the fruits improved their floating ability. Agitated upper fruit segments showed a significantly lower sinking index than agitated lower fruit segments and upper and lower fruit segments in the still treatment. The overwintering of fruits improved their floating ability.

VSIV (Vortex Self-Induced Vibration) Kinematics

2008 ◽  
Author(s):  
Antonio C. Fernandes ◽  
Erika M. C. Silva ◽  
Ricardo Franciss ◽  
Fabio M. Coelho ◽  
Severino F. S. Neto
Keyword(s):  
Graduate School ◽  
Transverse Direction ◽  
Horizontal Cylinder ◽  
Forced Oscillations ◽  
Lateral Motion ◽  
Steel Catenary Riser ◽  
The Past ◽  
Waves And Currents ◽  
Dimensional Parameters ◽  
A Current

The Vortex Induced Vibration (VIV) of cylindrical lines that may occur when the lines are submitted to currents has been extensively discussed in the past few years and its behavior has become well known. However, it is not so well known that the vibrations may occur in a current-less situation, induced by the lateral motion of the structure itself. The present work refers to the last as the Vortex Self-Induced Vibration, the VSIV. This occurrence has been made clear in the LOC/COPPE/UFRJ (Laboratory of Waves and Currents of COPPE, the Graduate School of Federal University of Rio de Janeiro) by specifically designed tests. In these tests, a totally submerged horizontal cylinder was submitted to harmonic forced oscillations, being free to move in the transverse direction of the forced excitation. The VSIV then showed up, with the cylinder segment, describing vertical trajectories in two (vertical 8-shape), three, four, etc., almost circular trajectories (called the rings in the work). Subsequently, the work shows that the measurements in full scale with the VIV bottle on a Steel Catenary Riser in the PETROBRAS 18 platform also indicate the existence of the VSIV. The tests were carried out with Keulegan-Carpenter equal to 10, 20 and 30 and for several amplitudes. The response of the cylinder was represented in non-dimensional parameters corresponding to the amplitude, the excitation and the response frequencies.

Large scale horizontal cylinder forces in waves and currents

1997 ◽  
Vol 19 (3-4) ◽  
pp. 211-223 ◽  
Author(s):  
J.R. Chaplin ◽  
K. Subbiah
Keyword(s):  
Large Scale ◽  
Horizontal Cylinder ◽  
Waves And Currents

Influence of Airflow Separation on the Turbulent Flow Structure Over Wind-Generated Water Waves

2009 ◽  
Author(s):  
Nasiruddin Shaikh ◽  
Kamran Siddiqui
Keyword(s):  
Reynolds Stress ◽  
Flow Separation ◽  
Water Waves ◽  
Separated Flow ◽  
Flow Fields ◽  
Velocity Fields ◽  
Transport Processes ◽  
Wave Crest ◽  
Two Dimensional ◽  
Momentum Exchange

An experimental study is conducted to investigate the airside flow behavior within the crest-trough region over wind generated water waves. Two-dimensional velocity fields in a plane perpendicular to the surface were measured using particle image velocimetry (PIV). The experiments were conducted in a wind wave flume 0.45 m wide, 0.9 m high and 3 m long. The measurements were made at a fetch of 2.1 m and at the wind speeds of 3.7 and 4.4 m s−1. An algorithm was developed to segregate separated and non-separated velocity fields within the measured dataset. The results show lower magnitudes of the streamwise velocity and higher magnitudes of Reynolds stress and turbulent kinetic energy for the separated flow fields than that for the non-separated flow fields, indicating that the flow separation significantly enhances turbulence in the near surface region. The enhanced Reynolds stress is positive which indicates that the flow separation increases downward momentum transfer from wind to the wave. The two dimensional plot of instantaneous velocity showed that the separation vortices are restricted to the region bounded by the wave crest and trough. The presented results demonstrate that the flow separation plays a significant role in the interfacial transport processes and therefore, it can be concluded that the understanding of the airflow field within the crest-trough region is vital to improve our knowledge about the air-water heat, mass and momentum exchange.

Hydrodynamic forces on a submerged cylinder advancing in water waves of finite depth

1991 ◽  
Vol 224 ◽  
pp. 645-659 ◽  
Author(s):  
G. X. Wu
Keyword(s):  
Water Waves ◽  
Outer Region ◽  
Finite Element Approximation ◽  
Finite Depth ◽  
Horizontal Cylinder ◽  
Hydrodynamic Forces ◽  
Boundary Integral ◽  
Circular Cylinders ◽  
Element Approximation ◽  
Field Equations

The hydrodynamic problem of a submerged horizontal cylinder advancing in regular water waves of finite depth at constant forward speed is analysed by the linearized velocity potential theory. The Green function is first derived. Far-field equations for calculating damping coefficients and exciting forces are obtained. The numerical method used combines a finite-element approximation of the potential in a region surrounding the cylinder with a boundary-integral-equation representation of the outer region. Numerical results for the hydrodynamic forces on submerged circular cylinders and elliptical cylinders are provided.

Nonlinear interactions between deep-water waves and currents

2011 ◽  
Vol 691 ◽  
pp. 1-25 ◽  
Author(s):  
R. M. Moreira ◽  
D. H. Peregrine
Keyword(s):  
Deep Water ◽  
Water Waves ◽  
Boundary Integral ◽  
Boundary Integral Method ◽  
Surface Velocity ◽  
Fully Nonlinear ◽  
Individual Wave ◽  
Waves And Currents ◽  
Wave Blocking ◽  
The Individual

AbstractThe effects of nonlinearity on a train of linear water waves in deep water interacting with underlying currents are investigated numerically via a boundary-integral method. The current is assumed to be two-dimensional and stationary, being induced by a distribution of singularities located beneath the free surface, which impose sharp and gentle surface velocity gradients. For ‘slowly’ varying currents, the fully nonlinear results confirm that opposing currents induce wave steepening and breaking within the region where a high convergence of rays occurs. For ‘rapidly’ varying currents, wave blocking and breaking are more prominent. In this case reflection was observed when sufficiently strong adverse currents are imposed, confirming that at least part of the wave energy that builds up within the caustic can be released in the form of partial reflection and wave breaking. For bichromatic waves, the fully nonlinear results show that partial wave blocking occurs at the individual wave components in the wave groups and that waves become almost monochromatic upstream of the blocking region.

scholarly journals SIMULTANEOUS WAVE AND CURRENT FORCES ON A PIPELINE

1980 ◽  
Vol 1 (17) ◽  
pp. 106
Author(s):  
David A. Knoll ◽  
John B. Herbich
Keyword(s):  
Small Diameter ◽  
Horizontal Cylinder ◽  
Random Wave ◽  
Ocean Bottom ◽  
Hydrodynamic Loads ◽  
Fluid Force ◽  
Interaction Of Waves ◽  
Drag Forces ◽  
Waves And Currents ◽  
A Current

The hydrodynamic loads on an offshore pipeline resting on the ocean bottom are a function of parameters associated with waves and currents acting near the pipeline. There have been many studies conducted to develop the criteria needed to estimate the hydrodynamic loads imposed by waves and currents. Many of these studies have investigated the effect of these phenomena individually, but to date only limited research has been directed towards evaluating the combined effect. In general, the investigations of the interaction of waves and currents and their effect on the fluid force have been directed toward vertical piles1'2'3'1*'5 and structures in a random wave field with a current present;6'7'8'9 however, the fluid force of waves in the presence of currents on pipelines has not been directly addressed. The purpose of this research was to investigate the interaction of waves and currents and its relationship to the forces on submerged pipelines. A model pipeline in a wave-flume was used to obtain experimental values which were compared to values predicted by the Morison equation in conjunction with the superposition of the waves and a current. The Morison equation10 was used to evaluate the forces on a horizontal cylinder resting on the bottom. The two major input parameters required by this equation are (1) the water particle kinematics of velocity and acceleration; and (2) the coefficients of drag and inertia. The testing program investigated the drag forces developed by the combined waves and a current. The inertia forces were assumed small when compared to the drag forces since a relatively small diameter cylinder was used in the experiments, thus the accelerations were small.

Power Extraction from Water Waves

1976 ◽  
Vol 20 (02) ◽  
pp. 63-66 ◽  
Author(s):  
Chiang C. Mei
Keyword(s):  
Water Waves ◽  
Degrees Of Freedom ◽  
Vertical Axis ◽  
Horizontal Cylinder ◽  
The Body ◽  
Floating Body ◽  
Maximum Efficiency ◽  
Viscous Effects ◽  
Two Degrees Of Freedom ◽  
Power Extraction

Salter has demonstrated experimentally that a horizontal cylinder in the free surface of water can be a device to extract energy from the incident waves. This paper proposes a design which is based on the idea of a tethered-float breakwater, and gives the theoretical design criteria for maximum power extraction from a general floating cylinder with one or two degrees of freedom. It is shown that the rate of energy extraction must be equal to the rate of radiation damping and that the floating body must be made to resonate then for a body with one degree of freedom, the maximum efficiency at a given frequency can be at leastone half if the body is symmetrical about a vertical axis, and greater for an asymmetrical body. For a body with two degrees of freedom, all the wave power can be extracted. Hydrodynamical aspects of the controlled motion are examined. Viscous effects are ignored.

THE MOVEMENT OF OIL SPILLS

1971 ◽  
Vol 1971 (1) ◽  
pp. 489-494 ◽  
Author(s):  
Henry G. Schwartzberg
Keyword(s):  
Wind Tunnel ◽  
Water Waves ◽  
Oil Spills ◽  
Wave Interaction ◽  
Open Water ◽  
Wind Drift ◽  
Calm Water ◽  
Waves And Currents ◽  
Infinite Height ◽  
Drift Analysis

ABSTRACT The effects of winds, waves, and currents, and the physical properties of oil and water on the drift rates of oil spills were studied in tests carried out in a combined water basin wind tunnel On calm water, oil drifted at a fairly constant percentage of the wind speed regardless of the nature and spreading tendencies of the oil, the spill size, and water temperature, depth, and salinity. Percent drift varied with wind tunnel height. Extrapolation to infinite height indicated that on calm open water wind drift should be 3.7%. Shallow water waves, which produced no significant drift themselves, reduced wind drift. Analysis indicated that deep water waves produced by the wind should produce significant drift, complicating wind drift prediction, but the magnitude of the wind wave interaction effects is not yet known. Test wind drifts and current drifts were found not to be directly additive.

CFD Parametric Study of Geometrical Variations on the Vortex-Induced Motions of Deep-Draft Semi-Submersibles

2018 ◽  
Author(s):  
Weiwen Zhao ◽  
Decheng Wan
Keyword(s):  
Parametric Study ◽  
Turbulence Modeling ◽  
Separated Flow ◽  
Design Parameters ◽  
Concept Design ◽  
Detached Eddy Simulation ◽  
Baseline Model ◽  
Geometry Model ◽  
Waves And Currents ◽  
Cfd Method

Vortex-Induced Motions (VIM) is a key issue for deep draft column stabilized floaters (DDCSF). An example of DDCSF is the concept design called Paired-Column semi-submersible (PC-Semi) with a pair of columns instead of single column at four corners of the platforms. The complex multi-column design involves several extra design parameters such as paired-column gaps and column cross-section areas than conventional semi-submersibles. These parameters can be tuned to mitigate dynamic response to waves and currents. However, it is expensive to perform parametric study of geometric variations by means of experiments. In the present work, CFD method is utilized to investigate the VIM characteristics for different geometrical variations of the PC-Semi. An in-house CFD code naoe-FOAM-SJTU, which is developed on top of the open source framework OpenFOAM, is used for all numerical simulations. Delayed detached-eddy simulation (DDES) is used for turbulence modeling with massively separated flow. A geometry model scaled at 1:54 from MARIN is select as the baseline model for parametric study. VIM simulations of the baseline model is firstly carried out and compared with experiments to validate the current CFD code. After that, VIM characteristics of paired-column gaps geometrical variations are numerically investigated. Motions of the platform and hydrodynamic forces on columns are compared and analyzed. The ability of CFD method in optimizing geometric design parameters on mitigating VIM response for deep-draft semi-submersibles is demonstrated.

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