scholarly journals SCOUR BEHIND CIRCULAR CYLINDERS IN DEEP WATER

1982 ◽  
Vol 1 (18) ◽  
pp. 93
Author(s):  
Jorg Imberger ◽  
Des Alach ◽  
John Schepis
Keyword(s):  
Test Data ◽  
Deep Water ◽  
Vertical Cylinder ◽  
Shear Velocity ◽  
Circular Cylinders ◽  
Marginal Value ◽  
Flume Test ◽  
Cylinder Diameter ◽  
Ocean Sediment

Flume test data is presented for the depth of scour in deep water near a vertical cylinder placed in a uniform sand and a fine calcareous ocean sediment. The ratio of the depth of scour to the cylinder diameter at equilibrium is shown to depend only on the ratio of the shear velocity to the critical shear velocity at which bed motion is initiated. Protection against scour by placing collars around the cylinder is shown to be of marginal value.

Decadal climate sensitivity of contouritic sedimentation in a dynamically coupled ice-ocean-sediment model of the Pan-Arctic region

2021 ◽  
Author(s):  
Catherine Drinkorn ◽  
Jan Saynisch-Wagner ◽  
Gabriele Uenzelmann-Neben ◽  
Maik Thomas
Keyword(s):  
Deep Water ◽  
Arctic Region ◽  
Meridional Overturning Circulation ◽  
Ocean Dynamics ◽  
Sedimentation Rates ◽  
Climate Conditions ◽  
The North ◽  
Ocean Sediment ◽  
Set Up ◽  
Sediment Model

<p>Ocean sediment drifts contain important information about past bottom currents but a direct link from the study of sedimentary archives to ocean dynamics is not always possible. To close this gap for the North Atlantic, we set up a  new coupled Ice-Ocean-Sediment Model of the entire Pan-Arctic region. In order to evaluate the potential dynamics of the model, we conducted decadal sensitivity experiments. In our model contouritic sedimentation shows a significant sensitivity towards climate variability for most of the contourite drift locations in the model domain. We observe a general decrease of sedimentation rates during warm conditions with decreasing atmospheric and oceanic gradients and an extensive increase of sedimentation rates during cold conditions with respective increased gradients. We can relate these results to changes in the dominant bottom circulation supplying deep water masses to the contourite sites under different climate conditions. A better understanding of northern deep water pathways in the Atlantic Meridional Overturning Circulation (AMOC) is crucial for evaluating possible consequences of climate change in the ocean.</p>

Near-field mean flow dynamics of a cylindrical canopy patch suspended in deep water

2018 ◽  
Vol 858 ◽  
pp. 634-655 ◽  
Author(s):  
Jian Zhou ◽  
Subhas K. Venayagamoorthy
Keyword(s):  
Deep Water ◽  
Near Field ◽  
Flow Dynamics ◽  
Flow Diversion ◽  
Circular Cylinders ◽  
Published Data ◽  
Global Flow ◽  
Mean Flow ◽  
Near Wake ◽  
Local Flow

The time-averaged flow dynamics of a suspended cylindrical canopy patch with a bulk diameter of $D$ is investigated using large-eddy simulations (LES). The patch consists of $N_{c}$ constituent solid circular cylinders of height $h$ and diameter $d$, mimicking patchy vegetation suspended in deep water ($H/h\gg 1$, where $H$ is the total flow depth). After validation against published data, LES of a uniform incident flow impinging on the canopy patch was conducted to study the effects of canopy density ($0.16\leqslant \unicode[STIX]{x1D719}=N_{c}(d/D)^{2}\leqslant 1$, by varying $N_{c}$) and bulk aspect ratio ($0.25\leqslant AR=h/D\leqslant 1$, by varying $h$) on the near-wake structure and adjustment of flow pathways. The relationships between patch geometry, local flow bleeding (three-dimensional redistribution of flow entering the patch) and global flow diversion (streamwise redistribution of upstream undisturbed flow) are identified. An increase in either $\unicode[STIX]{x1D719}$ or $AR$ decreases/increases/increases bleeding velocities through the patch surface area along the streamwise/lateral/vertical directions, respectively. However, a volumetric flux budget shows that a larger $AR$ causes a smaller proportion of the flow rate entering the patch to bleed out vertically. The global flow diversion is found to be determined by both the patch geometrical dimensions and the local bleeding which modifies the sizes of the patch-scale near wake. While loss of flow penetrating the patch increases monotonically with increasing $\unicode[STIX]{x1D719}$, its partition into flow diversion around and beneath the patch shows a non-monotonic dependence. The spatial extents of the wake, the flow-diversion dynamics and the bulk drag coefficients of the patch jointly reveal the fundamental differences of flow responses between suspended porous patches and their solid counterparts.

Approximation of Surge and Pitch Loads on Truncated Vertical Cylinders

2003 ◽  
Author(s):  
Keyvan Sadeghi ◽  
Atilla Incecik ◽  
Martin Downie ◽  
Hoi-Sang Chan
Keyword(s):  
Computer Program ◽  
Deep Water ◽  
Parametric Study ◽  
Unit Length ◽  
Diffraction Theory ◽  
Circular Cylinders ◽  
Offshore Platforms ◽  
Vertical Cylinders

Truncated vertical circular cylinders are used to make deep water floating offshore platforms like Truss Spars. When the draft of the cylindrical hull is not deep enough, prediction of the surge and pitch diffraction loads by integration of McCamy and Fuchs expression of the force per unit length over the cylinder draft causes an error which is not negligible. Using hydrodynamic arguments the approximated surge and pitch loads by McCamy and Fuchs diffraction theory are modified. The modified results are compared with the results of a parametric study using the computer program WaMIT 4.01 based on the linear diffraction theory, reported by Weggel [1].

Simulation of Angular Flow in a Shallow Basin Triggered by a Rotating Vertical Cylinder by SPH Method

2018 ◽  
Vol 881 ◽  
pp. 15-22
Author(s):  
Warniyati ◽  
Radianta Triatmadja ◽  
Nur Yuwono
Keyword(s):  
Numerical Model ◽  
Physical Model ◽  
Time Integration ◽  
Vertical Cylinder ◽  
Shear Velocity ◽  
Future Research ◽  
Sph Method ◽  
Virtual Particle ◽  
Real Particle ◽  
Particle Hydrodynamics

A simple numerical model has been generated for developing a code of Smoothed Particle Hydrodynamics (SPH) method. Those will be modified and used for future research. In this computational research domain is a square that consists of a real particle and virtual particle as the boundary treatment. In the initial condition, particle occupies a certain position. Circular flow has been generated by a rotating vertical cylinder to produce shear velocity to the real particle. The particles movement has been observed during time integration. A physical model has been constructed to compare the numerical model. The movement of real particles on the numerical model agrees with the movement of water particles on the physical model.

scholarly journals Horizontal Forces Due to Waves Acting on Large Vertical Cylinders in Deep Water

1972 ◽  
Vol 94 (4) ◽  
pp. 862-866
Author(s):  
E. R. Johnson
Keyword(s):  
Deep Water ◽  
Large Diameter ◽  
Wave Force ◽  
Circular Cylinders ◽  
Wave Forces ◽  
Typical Application ◽  
Model Studies ◽  
Horizontal Wave ◽  
Horizontal Wave Force ◽  
Vertical Cylinders

The special case of horizontal wave forces on large vertical cylinders in deep water is considered. The typical application for such a case is the calculation of horizontal forces on column stabilized floating ocean platforms. Existing literature discussing horizontal wave forces on cylinders does not generally agree on how to predict these forces. Since for large diameter cylinders in deep water the maximum force is completely inertial, the problem of deriving a solution is considerably simplified. In this study, an expression for the maximum horizontal wave force on large diameter circular cylinders mounted vertically in deep water has been analytically derived. Experimental model studies were also conducted and the resulting measured forces were within 20 percent of predicted forces. An example of how to predict horizontal wave forces using the methods of this report is given.

Effect of a Vibrating Upstream Cylinder on a Stationary Downstream Cylinder

1986 ◽  
Vol 108 (2) ◽  
pp. 180-184 ◽  
Author(s):  
M. Moriya ◽  
H. Sakamoto
Keyword(s):  
Reynolds Number ◽  
Transverse Vibration ◽  
Flow Patterns ◽  
Uniform Flow ◽  
Circular Cylinders ◽  
Tandem Arrangement ◽  
Cylinder Diameter ◽  
Spacing Ratio ◽  
Lock In

The flow around two circular cylinders in tandem arrangement in uniform flow where the upstream cylinder is forcibly vibrated in direction normal to the approach flow was experimentally studied at Reynolds number of 6.54 × 104. The spacing ratio 1/d (1: distance between centers of cylinders, d: diameter of circular cylinders) and the ratio of amplitude to cylinder diameter a/d (a: amplitude of transverse vibration of cylinder) were varied from 2 to 6 and 0 to 0.029 respectively. The effects of the vibration of the upstream cylinder on the downstream cylinder were discussed. In particular, two distinct “lock-in” regions were observed when the upstream cylinder was vibrated with a spacing ratio of 1/d = 3.0. The cylinder vibration was so effective even for a/d as small as 0.017 to cause two different flow patterns.

scholarly journals Numerical Simulation of Breaking Wave Loading on Standing Circular Cylinders with Different Transverse Inclined Angles

2020 ◽  
Vol 10 (4) ◽  
pp. 1347
Author(s):  
Sen Qu ◽  
Shengnan Liu ◽  
Muk Chen Ong ◽  
Shuzheng Sun ◽  
Huilong Ren
Keyword(s):  
Experimental Data ◽  
Vertical Cylinder ◽  
Wave Force ◽  
High Order ◽  
Numerical Results ◽  
Circular Cylinders ◽  
Wave Forces ◽  
Breaking Wave ◽  
Time Step ◽  
Inclined Angle

The purpose of this paper is to numerically simulate the breaking wave past a standing cylinder with different transverse inclined angles. The numerical simulations are carried out by solving the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with the k − ω S S T turbulence model. The air–water interface is captured using the Volume of Fluid (VOF) method. The convergence studies on the grid and time-step are performed by examining the total horizontal breaking wave forces on the vertical cylinder. The present numerical results have been validated with the published experimental data. A good agreement is obtained between the present numerical results and the experimental data in terms of the surface elevation and the horizontal breaking wave force. Moreover, the total horizontal breaking wave force is decomposed into low-order and high-order wave forces through Fast Fourier Transform (FFT). It is observed that the free surface elevations in front of the cylinder and the normalized high-order wave force have a minimum value when the transverse inclined angle of the cylinder is 45°. The secondary load causing the higher-harmonic ringing motion of structures is not observed when the cylinder is placed with the transverse inclined angles of 30° and 45°.

scholarly journals Interaction of a Solitary Wave with Vertical Fully/Partially Submerged Circular Cylinders with/without a Hollow Zone

2020 ◽  
Vol 8 (12) ◽  
pp. 1022
Author(s):  
Chih-Hua Chang
Keyword(s):  
Circular Cylinder ◽  
Solitary Wave ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Wave Model ◽  
Circular Cylinders ◽  
Cylinder Surface ◽  
Wave Elevation ◽  
Curvilinear Grid ◽  
Nonlinear Potential

In this article, a three-dimensional, fully nonlinear potential wave model is applied based on a curvilinear grid system. This model calculates the wave action on a fully/partially submerged vertical cylinder with or without a hollow zone. As basic verification, a solitary wave hitting a single fully or partially submerged circular cylinder is tested, and our numerical results agree with the experimental results obtained by others. The influence of cylinder immersion depth and size on the wave elevation change on the cylinder surface is considered. The model is also applied to investigate the wave energy of a solitary wave passing through a hollow circular cylinder to determine the effect of the size and draft on the wave oscillating in the hollow zone.

Interaction of a deep-water wave with a vertical cylinder: effect of self-excited vibrations on quantitative flow patterns

2007 ◽  
Vol 572 ◽  
pp. 189-217 ◽  
Author(s):  
M. OZGOREN ◽  
D. ROCKWELL
Keyword(s):  
Flow Structure ◽  
Deep Water ◽  
Water Wave ◽  
Large Scale ◽  
Wave Motion ◽  
Vertical Cylinder ◽  
Small Scale ◽  
Cylinder Surface ◽  
Deep Water Wave ◽  
Quantitative Flow

Interaction of a deep-water wave with a cylinder gives rise to ordered patterns of the flow structure, which are quantitatively characterized using a technique of high-image-density particle image velocimetry. When the cylinder is stationary, the patterns of instantaneous flow structure take on increasingly complex forms for increasing Keulegan--Carpenter number KC. These patterns involve stacking of small-scale vorticity concentrations, as well as large-scale vortex shedding. The time-averaged consequence of these patterns involves, at sufficiently high KC, an array of vorticity concentrations about the cylinder.When the lightly damped cylinder is allowed to undergo bidirectional oscillations, the trajectories can be classified according to ranges of KC. At low values of KC, the trajectory is elliptical, and further increases of KC allow, first of all, both elliptical and in-line trajectories as possibilities, followed by predominantly in-line and figure-of-eight oscillations at the largest value of KC.Representations of the quantitative flow structure, in relation to the instantaneous cylinder position on its oscillation trajectory, show basic classes of patterns. When the trajectory is elliptical, layers of vorticity rotate about the cylinder surface, in accordance with rotation of the relative velocity vector of the wave motion with respect to the oscillating cylinder. Simultaneously, the patterns of streamline topology take the form of large-scale bubbles, which also rotate about the cylinder. When the cylinder trajectory is predominantly in-line with the wave motion, generic classes of vortex formation and shedding can be identified; they include sweeping of previously shed vorticity concentrations past the cylinder to the opposite side. Certain of these patterns are directly analogous to those from the stationary cylinder.

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