Experimental Investigation on Vortex-Induced Vibration of Deep-Sea Risers of Different Excitation Water Depths

Quaternary deposits in six sediment cores from the Scotia Sea, Antarctica, were examined for the presence of volcanic ash layers. The cores were recovered from water depths of 3369-4025 m. Altogether, 23 ash layers were found, 18 of which have been investigated by electron-probe microanalysis. Deception Island is identified as the source of all the ash layers analyzed. The upper ash layer in each core can be correlated across all six cores, over a distance of -100 km, on the basis of its unusual bimodal composition, major oxide geochemistry and stratigraphie position. Two other ash layers can also be correlated between several of the cores.

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Numerical and Experimental Research on the Effect of Platform Heave Motion on Vortex-Induced Vibration of Deep Sea Top-Tensioned Riser

Shock and Vibration ◽

10.1155/2021/8866051 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Jie Zhang ◽

Ying Zeng ◽

Yougang Tang ◽

Wenyun Guo ◽

Zhenkui Wang

Keyword(s):

Parametric Excitation ◽

Deep Sea ◽

Frequency Component ◽

Vortex Induced Vibration ◽

Wake Oscillator ◽

Validation Experiment ◽

Simulation And Experiment ◽

Prediction And Control ◽

Heave Motion ◽

And Control

The prediction and control of vortex-induced vibration (VIV) is one of the key problems for riser design. The effect of platform heave motion on VIV of deep sea top-tensioned riser (TTR) is presented by means of numerical simulation and experiment in this research. First, the heave motion was modeled as a parametric excitation, and the governing equation of VIV of riser considering the parametric excitation was established. Then, the dynamic response of TTR was calculated numerically by the finite difference method based on the Van der Pol wake-oscillator model. Finally, a validation experiment was carried out at the towing tank of Tianjin university. The results show that the VIV response at the bottom of riser is significantly increased due to the platform heave motion, especially in the situation of low current velocity. The larger amplitude and the higher frequency of the platform heave motion with the greater influence are generated on VIV of TTR. In particular, the value of 0.5 times, 1 time, or other multiples of the platform heave frequency will be included in the vibration frequency component of TTR when the platform heave amplitude is large and the frequency is high.

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Innovative Experimental Investigation on the Influences of the Reynolds Number

10.5957/attc-2017-0056 ◽

2017 ◽

Author(s):

Jian Gu ◽

Antonio Carlos Fernandes

Keyword(s):

Experimental Investigation ◽

Reynolds Number ◽

Dimensionless Parameter ◽

Individual Effect ◽

Vortex Induced Vibration ◽

Industry Standards ◽

Experimental Facilities ◽

The Individual

The influences of Re (Reynolds number) on the response of vortex induced vibration (VIV) have been studied by previous researches, which indicate the influences should not be ignored. However, due to the limitation of experimental facilities and complexity of the cases, the explicit influence of Re on VIV is still not fully known. Meanwhile, the industry standards also do not supply design reference taking account of Re effects quantitatively. In present work, an innovative dimensionless parameter (denoted as “inertia-viscosity”) is proposed to displace the Re in the dimensionless system, in order to clarify the individual effect of Re. With this method, comparing tests are concisely carried out, and the effectiveness and feasibility are demonstrated. Through the comparing of tests, several remarkable results are obtained.

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New subgenus and new species of marine benthic ostracods of genus Doloria (Ostracoda; Myodocopina) from the Southern Ocean

Zootaxa ◽

10.11646/zootaxa.3356.1.1 ◽

2012 ◽

Vol 3356 (1) ◽

pp. 1 ◽

Cited By ~ 1

Author(s):

VLADIMIR G. CHAVTUR ◽

SIMONE N. BRANDÃO ◽

ALEXANDER G. BASHMANOV

Keyword(s):

New Species ◽

Southern Ocean ◽

Deep Sea ◽

Novel Species ◽

The Other ◽

The Novel ◽

Atlantic Sector ◽

New Subgenus ◽

Fifth Limb ◽

Water Depths

The project ANDEEP was designed to fill gaps in the knowledge of the biodiversity of the Southern Ocean deep sea. Threeoceanographic cruises (ANDEEP I, II and III) were undertaken in 2002 and 2005 in the Atlantic Sector of the SouthernOcean. Hundreds of samples were collected from 40 stations with water depths ranging from 748 to 6,348 m. Investiga-tions were carried out on a broad range of taxa, including bacteria, meio-, macroand megafauna. Approximately 5000ostracods were collected, which included 29 specimens of Doloria (Dolorietta) subgen. nov.The subdivision of the genus Doloria Skogsberg, 1920 into two subgenera, Doloria (Doloria) and the novel subgenusDoloria (Dolorietta), is based on differences in the structures of the fifth limb, the armature of the sensory bristle on the5th segment of the antennula, and the number of bristles on the 4th endite of the sixth limb. Four new species in the newsubgenus were identified from the ANDEEP samples. The new subgenus and the four novel species are described andillustrated. Two of these new species are named Doloria (Dolorietta) antarctica sp. nov. and Doloria (Dolorietta) sextafiliformis sp. nov., but the other two species are left in open nomenclature (i.e. Doloria (Dolorietta) sp. nov. 1 and Doloria(Dolorietta) sp. nov. 2) because only juveniles were found in our material. Keys to the subgenera and species of Doloria are provided.

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Active sediment creep deformation on a deep-sea terrace in the Japan Trench

Geological Magazine ◽

10.1017/s0016756818000894 ◽

2018 ◽

Vol 158 (1) ◽

pp. 39-46 ◽

Cited By ~ 2

Author(s):

Sayaka Nitta ◽

Takafumi Kasaya ◽

Kiichiro Kawamura

Keyword(s):

Active Region ◽

Creep Deformation ◽

Deep Sea ◽

Japan Trench ◽

Normal Faults ◽

Tectonic Erosion ◽

Active Folds ◽

Sequence Unit ◽

Water Depths ◽

Rising Sea Level

AbstractEighty-six new acoustic survey lines along and across the Japan Trench revealed active sediment creep deformation on a deep-sea terrace at water depths of 400–1200 m in an area of arcuate-shaped depressions that are probably associated with tectonic erosion. The most active region of creep is located on the top at the surface of the depression south of 38° N. The area of creep deformation is characterized by arcuate-shaped topographic lineaments with active folds and active normal faults stepping down trenchward. In contrast to the southern region, normal faults at the top of the depression north of 38° N cut a sedimentary sequence (Unit 1) that is acoustically transparent with continuous weak reflectors, and this is covered by the undeformed layered sediment sequence of Unit 2. Unit 2 corresponds to the period of rising sea level that extended from the latest Pleistocene to the early Holocene (14–6 ka). Thus, creep is ongoing at the top of the depression south of 38° N in the surface layer, whereas it stopped north of the depression between 14 and 6 ka. These observations might indicate that the active region jumped from north to south due to probably retrogressive sliding.

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