Computational Simulations of Deep Water Currents and 3D Waves with Submerged Structures

2008 ◽  
Author(s):  
M Ucuncu ◽  
◽  
F Dufour ◽  
J Morgan ◽  
◽  
...  
Keyword(s):  
Deep Water ◽  
Computational Simulations ◽  
Water Currents ◽  
3D Waves

Turkstra Profiles of North Sea Currents: Wider Than You’d Think

2011 ◽  
Author(s):  
Steven R. Winterstein ◽  
Sverre Haver ◽  
Alok K. Jha ◽  
Borge Kvingedal ◽  
Einar Nygaard
Keyword(s):  
North Sea ◽  
Deep Water ◽  
Current Speed ◽  
Marine Structures ◽  
Marginal Analysis ◽  
Water Currents ◽  
Extreme Loads ◽  
Peak Over Threshold ◽  
Direct Contrast ◽  
Sea Currents

To design marine structures in deep water, currents must be modelled accurately as a function of depth. These models often take the form of T-year profiles, which assume the T-year extreme current speed occurs simultaneously at each depth. To better reflect the spatial correlation in the current speeds versus depth, we have recently introduced Turkstra current profiles. These assign the T-year speed at one depth, and “associated” speeds expected to occur simultaneously at other depths. Two essentially decoupled steps are required: (1) marginal analysis to estimate T-year extremes, and (2) some type of regression to find associated values. The result is a set of current profiles, each of which coincides with the T-year profile at a single depth and is reduced elsewhere. Our previous work with Turkstra profiles suggested that, when applied in an unbiased fashion, they could produce unconservative estimates of extreme loads. This is in direct contrast to the findings of Statoil, whose similar (“CCA”) current profiles have generally been found to yield conservative load estimates. This paper addresses this contradiction. In the process, we find considerable differences can arise in precisely how one performs steps 1 and 2 above. The net finding is to favor methods that properly emphasize the upper tails of the data—e.g., using peak-over-threshold (“POT”) data, and regression based on class means—rather than standard analyses that weigh all data equally. By applying such tail-sensitive methods to our dataset, we find the unconservative trend in Turkstra profiles to essentially vanish. For our data, these tail-fit results yield profiles with both larger marginal extremes, and broader profiles surrounding these extremes—hence the title of this paper.

William Scoresby as an Arctic physical oceanographer

2019 ◽  
Vol 46 (1) ◽  
pp. 33-43 ◽  
Author(s):  
C. Leah Devlin
Keyword(s):  
Deep Water ◽  
Water Movement ◽  
The Arctic ◽  
Water Currents ◽  
Arctic Regions ◽  
European Arctic ◽  
North Polar ◽  
The Times ◽  
Personal Library ◽  
Arctic Science

Encouraged by naturalists Robert Jameson and Joseph Banks, whaler William Scoresby became an expert on the natural and physical processes at work in the European Arctic. Original letters between Scoresby and these naturalists, housed in the archive of the Whitby Literary and Philosophical Society (Yorkshire, England), document in the language of the times his biological observations and experiments in physical oceanography. Scoresby's researches resulted in An Account of the Arctic Regions, with a History and Description of the Northern Whale-fishery in 1820, which became a seminal work in Arctic science. Among the prescient observations in An Account of the Arctic Regions was a description of deep strata of water, under currents moving in different directions from the surface. A copy of An Account of the Arctic Regions was given as a gift to Norwegian scientist-explorer Fridtjof Nansen in 1897 upon the completion of the Fram expedition (1893–1896) and still resides in his personal library in Norway. In it is an underlined passage, suggesting that Nansen had read the whaler's book, perhaps in preparation for writing his own volumes on Arctic science, The Norwegian North Polar Expedition, 1893–1896 (1900–1906). Then, by inference, Nansen had been familiar with Scoresby's description of the under currents. In The Norwegian North Polar Expedition Nansen wrote that he had observed similar patterns of deep-water movements during the Fram expedition. This phenomenon must have perplexed him, because he posed the problem to the Swedish mathematician-oceanographer Vagn Walfrid Ekman, who mathematically described the water movement. Ekman's resulting model, a spiral staircase of descending deep-water currents, became known as the Ekman Spiral.

scholarly journals Theoretical and experimental investigations of wave field around vessel in shallow water

2020 ◽  
pp. 72-89
Author(s):  
Н.В. Єфремова ◽  
A.Є. Нильва ◽  
Н.Н. Котовська ◽  
М.В. Дрига
Keyword(s):  
Shallow Water ◽  
Deep Water ◽  
Theoretical Data ◽  
Experimental Investigations ◽  
Arbitrary Angle ◽  
Actual Problem ◽  
Transformation Zone ◽  
Non Linear ◽  
The Waves ◽  
3D Waves

Un-running vessel at the shallow-water road anchorage is under exposure to waves that come at arbitrary angle from the high sea. 3D waves from deep-sea area become practically 2D when entering shallow water. While mean periods are kept, waves become shorter and their crests become higher and sharpener than for deep-water ones. As a result of diffraction of waves that come from the deep-water sea at the vessel, a transformation zone appears where waves become 3D again. Dimensions of the waves’ transformation zone, character and height of waves in this zone specify safety of auxiliary crafts, e.g. tugboats, bunker vessels, pilot and road crafts, oil garbage collectors and boom crafts. In the complex 3D waves the trajectory of auxiliary vessel’s movement has to be safe, vessel’s motions have to be moderate. Besides waves’ height is one of the parameters that are used for forecast of movement of spilled oil. Last years the biggest part examination of waves’ problems was devoted to estimation of waves’ impact onto stationary or floating shelf facilities. For validity estimation, waves’ characteristics defined due to different theories, are compared with experimental ones. But characteristics of the waves around shelf facilities are hardly able to be compared to same ones of waves around bodies with vessel-type shape.  At the experiments with vessels’ models, waves’ impact onto vessel was examined, but not the transformation of the waves themselves. So, comparing of waves area’s characteristics defined by both theoretical experimental ways is an actual problem.  Aim of the paper is verification of results of wave area investigation; wave area is located around a vessel that is exposed of arbitrary angle waves at shallow water conditions. Description of experimental investigations of transformed waves in the towing tank is done; transformation zone appears around vessel’s model while running waves diffract on it. Distribution of waves’ amplitudes at the designated points was fixed by the special designed and manufactured unit. Experimental data is compared with computation results both of linear and non-linear theories. It was assumed that experimental results and theoretical data satisfactory meet each other; also that non-linear computations define the maximal values of waves’ amplitudes at all cases.

On Dense Bottom Currents in the Baltic Deep Water

1977 ◽  
Vol 8 (5) ◽  
pp. 297-316 ◽  
Author(s):  
Flemming Bo Pedersen
Keyword(s):  
Deep Water ◽  
Oxygen Supply ◽  
Bottom Current ◽  
Bornholm Basin ◽  
Bottom Currents ◽  
Water Currents ◽  
Baltic Proper ◽  
The Baltic

A rational entrainment function for a subcritical dense bottom current is outlined. As an example the formula has been used to some orders of magnitude calculations of the deep water currents from the Darss Sill to the Stolpe Channel. It is shown that the salt and oxygen supply to the deep water of the Baltic Proper during a »normal« year stems from this bottom current and its entrained water. The renewal of the deep water in the Baltic Proper can be traced in the Bornholm Basin, and hence it is strongly recommended, that continous measurements of salinity, temperature, oxygen, phosphate etc. are performed in the Bornholm Basin, especially in the highly entraining area just north of Bornholm.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

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