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.

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.

scholarly journals SCOUR ABOUT A SINGLE, CYLINDRICAL PILE DUE TO COMBINED RANDOM WAVES AND A CURRENT

1986 ◽  
Vol 1 (20) ◽  
pp. 136 ◽  
Author(s):  
Robert W. Eadie ◽  
John B. Herbich
Keyword(s):  
Random Wave ◽  
Two Dimensional ◽  
Random Waves ◽  
Sediment Size ◽  
Waves And Currents ◽  
Using Data ◽  
Almost All ◽  
A Current ◽  
Water Depths ◽  
Monochromatic Waves

There have been many studies of scour around piles caused by waves, and some studies of scour by waves and currents combined. However, almost all of the studies were conducted with monochromatic waves. The purpose of this investigation was to study what scouring effects various currents and random waves have on a single, cylindrical pile. These results were then compared with the results from previous studies of scour resulting from currents and monochromatic waves at Texas A&M University (Armbrust, 1982 and Wang, 1983). Experiments were conducted in a two-dimensional wave tank. The pile used in this study had a diameter of 1.5 inches. Two water depths, four currents, one sediment size and four random wave spectra were utilized. Using data obtained from the experiments, an attempt was made to describe scour in terms of relevant dimensionless parameters.

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

scholarly journals Random wave-driven drag forces on near-bed vegetation in shallow water based on deepwater wind conditions

2019 ◽  
Vol 233 (4) ◽  
pp. 1287-1290
Author(s):  
Dag Myrhaug
Keyword(s):  
Shallow Water ◽  
Drag Force ◽  
Wind Waves ◽  
Wave Spectrum ◽  
Random Wave ◽  
Random Waves ◽  
Coastal Zones ◽  
Drag Forces ◽  
Mean Wind Speed ◽  
Wave Induced

This article provides a simple analytical method for giving estimates of random wave-driven drag forces on near-bed vegetation in shallow water from deepwater wind conditions. Results are exemplified using a Pierson–Moskowitz model wave spectrum for wind waves with the mean wind speed at the 10 m elevation above the sea surface as the parameter. The significant value of the drag force within a sea state of random waves is given, and an example typical for field conditions is presented. This method should serve as a useful tool for assessing random wave-induced drag force on vegetation in coastal zones and estuaries based on input from deepwater wind conditions.

445 Fluid Force Acting on a Sphere in a Small-diameter Tube

2003 ◽  
Vol 2003 (0) ◽  
pp. _445-1_-_445-6_
Author(s):  
Takuro TOMIMATSU ◽  
Tsukasa YONEYAMA ◽  
Shinichi MARUYAMA ◽  
Masatsugu YOSHIZAWA
Keyword(s):  
Small Diameter ◽  
Fluid Force

scholarly journals Interaction of waves and currents with kelp forests (Macrocystis pyrifera ): Insights from a dynamically scaled laboratory model

2013 ◽  
Vol 58 (3) ◽  
pp. 790-802 ◽  
Author(s):  
Johanna H. Rosman ◽  
Mark W. Denny ◽  
Robert B. Zeller ◽  
Stephen G. Monismith ◽  
Jeffrey R. Koseff
Keyword(s):  
Macrocystis Pyrifera ◽  
Laboratory Model ◽  
Kelp Forests ◽  
Interaction Of Waves ◽  
Waves And Currents

Changes of the mean velocity profiles in the combined wave–current motion described in a GLM formulation

1998 ◽  
Vol 370 ◽  
pp. 271-296 ◽  
Author(s):  
J. GROENEWEG ◽  
G. KLOPMAN
Keyword(s):  
Velocity Profiles ◽  
Perturbation Series ◽  
Wave Crest ◽  
Mean Velocity ◽  
Initial Current ◽  
Eulerian Formulation ◽  
Waves And Currents ◽  
The Mean ◽  
The Waves ◽  
A Current

The generalized Lagrangian mean (GLM) formulation is used to describe the interaction of waves and currents. In contrast to the more conventional Eulerian formulation the GLM description enables splitting of the mean and oscillating motion over the whole depth in an unambiguous and unique way, also in the region between wave crest and trough. The present paper deals with non-breaking long-crested regular waves on a current using the GLM formulation coupled with a WKBJ-type perturbation-series approach. The waves propagate under an arbitrary angle with the current direction. The primary interest concerns nonlinear changes in the vertical distribution of the mean velocity due to the presence of the waves, but modifications of the orbital velocity profiles, due to the presence of a current, are considered as well. The special case of no initial current, where waves induce a so-called drift velocity or mass-transport velocity, is also studied.

Extreme Waves in Sea States Crossing an Oblique Current

2010 ◽  
Author(s):  
A. Toffoli ◽  
A. V. Babanin ◽  
F. Ardhuin ◽  
M. Benoit ◽  
E. M. Bitner-Gregersen ◽  
...  
Keyword(s):  
Nonlinear Dynamics ◽  
Gravity Waves ◽  
Laboratory Experiments ◽  
Random Wave ◽  
Extreme Waves ◽  
Regular Waves ◽  
Wave Fields ◽  
Surface Gravity Waves ◽  
Directional Wave ◽  
A Current

Laboratory experiments have been carried out in the directional wave tank at Marintek (Norway) to study the nonlinear dynamics of surface gravity waves and the occurrence of extreme events, when the wave field traverses obliquely an ambient current. A condition of partial opposition has been considered. Tests on regular waves have shown that the current can trigger the formation of large amplitude waves. In random wave fields, however, this only results in a weak deviation from the statistical properties observed in absence of a current.

Condensation on a Downward-facing Horizontal Rippled Surface

1972 ◽  
Vol 94 (3) ◽  
pp. 315-320 ◽  
Author(s):  
Avram Markowitz ◽  
B. B. Mikic ◽  
A. E. Bergles
Keyword(s):  
Experimental Data ◽  
Small Diameter ◽  
Horizontal Cylinder ◽  
Analytical Investigation ◽  
Film Condensation ◽  
Radius Of Curvature ◽  
Condensation Rate ◽  
Projected Area ◽  
Condensate Film ◽  
Constant Radius

An analytical investigation is presented for film condensation on a downward-facing horizontal doubly rippled surface. Small undulations having constant radius of curvature are combined with larger cylindrical grooves designed to aid condensate runoff. A direct expression for the condensate film thickness at the top of an undulation crest, as well as on a small-diameter horizontal cylinder, is derived. An upper-bound expression for the condensation rate on the rippled surface is then obtained which predicts that the condensation rate will be five times the rate attainable on a flat horizontal surface of the same projected area. This analytical expression is compared with experimental data.

Experimental Studies and Numerical Modeling of Copper Nets in Marine Environment

2011 ◽  
Author(s):  
Igor Tsukrov ◽  
Andrew Drach ◽  
Judson DeCew ◽  
M. Robinson Swift ◽  
Barbaros Celikkol ◽  
...  
Keyword(s):  
Marine Environment ◽  
Copper Alloy ◽  
Flexible Structures ◽  
Experimental Studies ◽  
Finite Element Program ◽  
Drag Forces ◽  
Waves And Currents ◽  
Element Program ◽  
Marine Applications ◽  
Increased Strength

Copper alloy netting is increasingly used for offshore aquaculture, harbor protection and other marine applications. Its advantageous characteristics include high resistance to biofouling and increased strength compared to polymer nets. However, the hydrodynamic properties of copper nets are not well studied. In this paper, the results of experimental studies of drag forces on copper alloy net panels are reported. Based on these studies, empirical values for drag coefficients are proposed for various types of copper nets, and compared to the corresponding data for polymer netting. It is shown that copper nets exhibit significantly lower resistance to the current flow which corresponds to lower values of drag coefficient. Coefficients obtained from the experiments are incorporated into the finite element program Aqua-FE, developed at the University of New Hampshire for analysis of flexible structures subjected to waves and currents in marine environment. The results of the numerical simulations for a small volume fish cage, subjected to two different sets of environmental conditions, are analyzed to compare how introduction of copper netting instead of traditional nylon nets affects the dynamic response of the system.

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