scholarly journals DRIFT CURRENTS OF CLEAN AND SLICK SEA SURFACES

1982 ◽  
Vol 1 (18) ◽  
pp. 143
Author(s):  
Jin Wu
Keyword(s):  
Surface Film ◽  
Offshore Structures ◽  
Sea Surface ◽  
Clean Surface ◽  
Dynamic Interactions ◽  
Drift Current ◽  
Stress Coefficient ◽  
Wind Velocities ◽  
Wave Induced ◽  
Surface Drift

Drift currents near sea surface govern movement and dispersion of man-made discharges near the sea surface, and influence design, deployment, and stability of offshore structures. The wind-induced drift currents and the wave-induced mass transports at the sea surface are separately estimated. The total surface drift current, the sum of wind- and wave-induced components, agree well with oceanic data (Hughes, 1956). The mass transport of waves over slick surface is greater than that over clean surface due to dynamic interactions between the surface film and waves. On the other hand, the wind-stress coefficient of slick surface is smaller than that of clean surface, resulting in a smaller wind-induced drift current over the slick surface. Available laboratory results (Alofs and Reisbig, 1972) on slick movements are reanalyzed to provide basis for estimating movements of slicks of various sizes over waves of different lengths under different wind velocities.

Laboratory studies of wind–wave interactions

1968 ◽  
Vol 34 (1) ◽  
pp. 91-111 ◽  
Author(s):  
Jin Wu
Keyword(s):  
Surface Roughness ◽  
Wind Stress ◽  
Water Surface ◽  
Wind Wave ◽  
Wave Drag ◽  
Average Height ◽  
Drift Current ◽  
Stress Coefficient ◽  
Wide Range ◽  
Wind Velocities

The present study consists of wind profile surveys, drift current measurements and water surface observations for a wide range of wind velocities in a wind–wave tank. It is confirmed that the velocity distribution essentially follows the logarithmic law near the water surface and the velocity-defect law toward the outer edge of the boundary layer. The wind stresses and surface roughnesses calculated from these distributions are divided into two groups separated by the occurrence of the wave-breaking phenomenon. For low wind velocities the surface roughness is dictated by ripples, and the wind-stress coefficient varies with U0−½, where U0 is the free-stream wind velocity. The surface roughness is proportional to the average height of the basic gravity wave at higher wind velocities; the stress coefficient is then proportional to U0. In addition, it is found that Charnock's expression (k ∝ u*2/g) holds only at high wind velocities, and that the constant of proportionality determined from the present experiment correlates very well with field observations. A new technique, involving the use of various-sized surface floats to determine the drift current gradient and the surface drift current, has been developed. A good agreement is shown between the gradients obtained from the measured currents and those determined from the wind stresses. Finally, the wind-stress coefficient is shown to be larger than the friction coefficient for turbulent flow along a solid rough surface; the difference is shown to be the wave drag of the wind over the water surface.

Stability of offshore structures in shallow water depth

2011 ◽  
Vol 2 (2) ◽  
pp. 320-333
Author(s):  
F. Van den Abeele ◽  
J. Vande Voorde
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Fossil Fuels ◽  
Oil And Gas ◽  
Structural Response ◽  
Offshore Structures ◽  
Exploration And Production ◽  
Subsea Pipelines ◽  
Wave Induced ◽  
Shallow Water Depth

The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.

Evolution of natural sea surface film structure as a tool for organic matter dynamics tracing

2008 ◽  
Vol 74 ◽  
pp. S52-S64 ◽  
Author(s):  
Z. Adriana Mazurek ◽  
J. Stanisław Pogorzelski ◽  
Katarzyna Boniewicz-Szmyt
Keyword(s):  
Organic Matter ◽  
Surface Film ◽  
Film Structure ◽  
Sea Surface ◽  
Organic Matter Dynamics

scholarly journals Elastic Properties of Natural Sea Surface Films Incorporated with Solid Dust Particles: Model Baltic Sea Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Adriana Z. Mazurek ◽  
Stanisław J. Pogorzelski
Keyword(s):  
Baltic Sea ◽  
Surface Film ◽  
Contact Angles ◽  
Solid Particles ◽  
Sea Surface ◽  
Dust Particles ◽  
Surface Films ◽  
Particle Removal ◽  
Water Contact ◽  
Composite Surface

Floating dust-originated solid particles at air-water interfaces will interact with one another and disturb the smoothness of such a composite surface affecting its dilational elasticity. To quantify the effect, surface pressure (Π) versus film area (A) isotherm, and stress-relaxation (Π-time) measurements were performed for monoparticulate layers of the model hydrophobic material (of μm-diameter and differentiated hydrophobicity corresponding to the water contact angles (CA) ranging from 60 to 140°) deposited at surfaces of surfactant-containing original seawater and were studied with a Langmuir trough system. The composite surface dilational modulus predicted from the theoretical approach, in which natural dust load signatures (particle number flux, daily deposition rate, and diameter spectra) originated from in situ field studies performed along Baltic Sea near-shore line stations, agreed well with the direct experimentally derived data. The presence of seawater surfactants affected wettability of the solid material which was evaluated with different CA techniques applicable to powdered samples. Surface energetics of the particle-subphase interactions was expressed in terms of the particle removal energy, contact cross-sectional areas, collapse energies, and so forth. The hydrophobic particles incorporation at a sea surface film structure increased the elasticity modulus by a factor K (1.29–1.58). The particle-covered seawater revealed a viscoelastic behavior with the characteristic relaxation times ranging from 2.6 to 68.5 sec.

scholarly journals Wave-Induced Seabed Response around a Dumbbell Cofferdam in Non-Homogeneous Anisotropic Seabed

2019 ◽  
Vol 7 (6) ◽  
pp. 189 ◽  
Author(s):  
Linya Chen ◽  
Dong-Sheng Jeng ◽  
Chencong Liao ◽  
Dagui Tong
Keyword(s):  
Shear Modulus ◽  
Vertical Distribution ◽  
Pore Pressure ◽  
Wave Structure ◽  
Offshore Structures ◽  
Hydrodynamic Process ◽  
Response Analysis ◽  
Depth Function ◽  
Wave Induced ◽  
The Vertical Distribution

Cofferdams are frequently used to assist in the construction of offshore structures that are built on a natural non-homogeneous anisotropic seabed. In this study, a three-dimensional (3D) integrated numerical model consisting of a wave submodel and seabed submodel was adopted to investigate the wave–structure–seabed interaction. Reynolds-Averaged Navier–Stokes (RANS) equations were employed to simulate the wave-induced fluid motion and Biot’s poroelastic theory was adopted to control the wave-induced seabed response. The present model was validated with available laboratory experimental data and previous analytical results. The hydrodynamic process and seabed response around the dumbbell cofferdam are discussed in detail, with particular attention paid to the influence of the depth functions of the permeability K i and shear modulus G j . Numerical results indicate that to avoid the misestimation of the liquefaction depth, a steady-state analysis should be carried out prior to the transient seabed response analysis to first determine the equilibrium state caused by seabed consolidation. The depth function G j markedly affects the vertical distribution of the pore pressure and the seabed liquefaction around the dumbbell cofferdam. The depth function K i has a mild effect on the vertical distribution of the pore pressure within a coarse sand seabed, with the influence concentrated in the range defined by 0.1 times the seabed thickness above and below the embedded depth. The depth function K i has little effect on seabed liquefaction. In addition, the traditional assumption that treats the seabed parameters as constants may result in the overestimation of the seabed liquefaction depth and the liquefaction area around the cofferdam will be miscalculated if consolidation is not considered. Moreover, parametric studies reveal that the shear modulus at the seabed surface G z 0 has a significant influence on the vertical distribution of the pore pressure. However, the effect of the permeability at the seabed surface K z 0 on the vertical distribution of the pore pressure is mainly concentrated on the seabed above the embedded depth in front and to the side of the cofferdam. Furthermore, the amplitude of pore pressure decreases as Poisson’s ratio μ s increases.

Sea foam as an object of sea-surface film studies

1997 ◽  
Vol 16 (2) ◽  
pp. 117-121 ◽  
Author(s):  
NIKOLAI V. DRUZHKOV ◽  
PAVEL R. MAKAREVICH ◽  
SERGEI I. BARDAN
Keyword(s):  
Film Studies ◽  
Surface Film ◽  
Sea Surface

scholarly journals Changes in Ocean Heat Content Caused by Wave-Induced Mixing in a High-Resolution Ocean Model

2018 ◽  
Vol 48 (5) ◽  
pp. 1139-1150 ◽  
Author(s):  
Lachlan Stoney ◽  
Kevin J. E. Walsh ◽  
Steven Thomas ◽  
Paul Spence ◽  
Alexander V. Babanin
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Heat Content ◽  
Circulation Model ◽  
Additional Term ◽  
Ocean Model ◽  
Ocean Heat Content ◽  
Sea Surface ◽  
Wave Heights ◽  
Wave Induced

Abstract A parameterization of turbulent mixing from unbroken surface waves is included in a 16-yr simulation within a high-resolution ocean circulation model (MOM5). This “surface wave mixing” (SWM) derives from the wave orbital motion and is parameterized as an additional term in a k-epsilon model. We show that SWM leads to significant changes in sea surface temperatures but smaller changes in ocean heat content, and show the extent to which these changes can reduce pre-existing model biases with respect to observed data. Specifically, SWM leads to a widespread improvement in sea surface temperature in both hemispheres in summer and winter, while for ocean heat content the improvements are less clear. In addition, we show that introducing SWM can lead to an accumulation of wave-induced ocean heat content between years. While it has been well established that secular positive trends exist in global wave heights, we find that such trends are relatively unimportant in driving the accumulation of wave-induced ocean heat content. Rather, in response to the new source of mixing, the simulated ocean climate evolves toward a new equilibrium with greater total ocean heat content.

Wave-Induced Damping of Offshore Structures

1987 ◽  
Author(s):  
A.B. Dunwoody ◽  
J.K. Vandiver
Keyword(s):  
Offshore Structures ◽  
Wave Induced
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