Investigation of a longfin inshore squid's swimming characteristics and an underwater locomotion during acceleration

In the present study, locomotion of a real longfin inshore squid (Doryteuthis pealeii) was numerically investigated. Geometry of a real squid was obtained using computed tomography (CT) images. In addition to a two-dimensional axisymmetric squid model, a modified squid model with no cavities around her head and an ellipse shaped model were generated with a fineness ratio (the ratio of body length to maximum body diameter) of 7.56. These numerical models were exposed to an acceleration with two different velocity programs. Added mass and basset forces on bodies were calculated during acceleration of the squid models starting from rest. Pressure and viscous drag forces were also calculated due to pressure variation along the squid models and friction on the surface of the models. The effect of a nozzle diameter on jet velocities and propulsive efficiency at all bodies were evaluated when time dependent velocity profiles (from 0 to 10 m/s in 0.5 and 1 s time durations) were set for the inlet of computational domain. The modified squid model required least thrust force during acceleration phase of time dependent velocity profile compared to the other models while the 0.02 m nozzle diameter provided largest propulsive efficiency for all models.     

Ocean currents determine functional connectivity in an Antarctic deep‐sea shrimp

The coherency among larval stages of marine taxa, ocean currents and population connectivity is still subject to discussion. A common view is that organisms with pelagic larval stages have higher dispersal abilities and therefore show a relatively homogeneous population genetic structure. Contrary to this, local genetic differentiation is assumed for many benthic direct developers. Specific larval or adult migratory behavior and hydrographic effects may significantly influence distribution patterns, rather than passive drifting abilities alone. The Southern Ocean is an ideal environment to test for the effects of ocean currents on population connectivity as it is characterized by several well‐defined and strong isolating current systems. In this study we studied the genetic structure of the decapod deep‐sea shrimp Nematocarcinus lanceopes, which has planktotrophic larval stages. We analysed 194 individuals from different sample localities around the Antarctic continent using nine microsatellite markers. Consistent with a previous study based on mitochondrial DNA markers, primarily weak genetic patterns among N. lanceopes populations around the continent were found. Using ocean resistance modeling approaches we were able to show that subtle genetic differences among populations are more likely explained by ocean currents rather than by geographic distance for the Atlantic Sector of the Southern Ocean.     

日本囊对虾(Marsupenaeus japonicus)秋繁仔虾形态表型与抗流性能间的相关性

于水温(18.0±1.0)°C、盐度20、pH 8.1±0.2条件下,以水流为胁迫因子(时长1min),以日本囊对虾秋繁同生群仔虾[总长(7.643±0.639)mm]为实验对象,以溢水口(实验初始时刻仔虾放置处)为起点,按等距离间距法将自制的水流测定装置(总长1m)依次划分为A(0—25cm)、B(25—50cm)、C(50—75cm)、D(75—100cm)和E(100cm)等五个区段,在确认实验终了时刻分布于A区段内仔虾数量占实验仔虾总数5%的水流速度为0.823cm/s后,以此为实验流速,借助显微扫描像素测量技术和多元分析方法定量研究了A、B、C、D、E实验群体(依次为实验终止时刻分布于A、B、C、D、E区段内的仔虾)个体间形态比例性状间的差异。结果表明:(1)在所涉15项形态测量指标中,各实验群体间均无显著差异(P0.05)的形态性状共计8项,依次为X_4(眼径)、X_5(头胸甲长)、X_6(头胸甲高)、X_7(第一腹节长)、X_8(第二腹节长)、X_9(第三腹节长)、X_~(10)(第四腹节长)和X_14(腹节高);(2)在所涉17项形态比例指标中,实验群体间均无显著差异(P0.05)的形态比例性状共计7项,依次为C_2(额剑长/总长)、C_9(第五腹节长/总长)、C_(10)(尾节长/总长)、C_(11)(尾扇长/总长)、C_(15)(头胸甲高/头胸甲长)、C_(16)(腹节高/第一腹节长)和C_(17)(尾节高/尾节长);(3)经主成分分析,提取到的5个特征值均大于1的主成分,累计贡献率达80.795%,其中第1主成分39.561%,其载荷绝对值大于0.5的主要影响变量占形态比例性状总数的47.059%;(4)将A实验群体定义为水流胁迫处理选留群,B、C、D、E实验群体统归为水流胁迫处理淘汰群。采用逐步判别法,以判别贡献率较大的C_1(第一触角柄长/总长)、C3(眼径/总长)、C7(第三腹节长/总长)、C13(额剑长/头胸甲长)为自变量,所建的Fisher分类函数方程组可较清晰地区分淘汰群和选留群个体,其中选留群的判别准确率P_1、P_2分别为98%和84.85%,淘汰群的判别准确率P_1、P_2分别为82.25%和97.63%,两者综合判别准确率为90.12%。综上可知,借助形态表型分型可实现日本囊对虾仔虾不同抗流性能群体间的筛选。     

使用多普勒超声成像比较栉孔扇贝与虾夷扇贝循环生理特征

将先进的多普勒超声成像技术运用于栉孔扇贝(Chlamys farreri)和虾夷扇贝(Patinopecten yessoensis)循环生理学的研究中,首次量化了扇贝心率(HR)、血流加速度(ABF)、收缩峰值速度(PS)、舒张末期速度(ED)、血液最大瞬时血流量(Max-IBF)、血液最小瞬时流量(Min-IBF)、收缩期与舒张期流速比(S/D)和阻力指数(RI)等指标,对比了两种不同耐温性扇贝的循环生理指标差异。结果表明,两种扇贝HR、ABF、PS、ED、Max-IBF、Min-IBF与水温均呈正相关;在10—25°C间,栉孔扇贝和虾夷扇贝HR范围分别为16—39、14—31次/min,ABF范围分别为1.75—15.84、0.99—7.41cm/s2,PS范围分别为3.54—8.09、2.32—8.85cm/s,ED范围分别为1.51—3.15、1.09—4.23cm/s,Max—IBF范围分别为0.051—0.193、0.137—0.316m L/s、Min—IBF范围分别为0.025—0.072、0.022—0.131m L/s、RI范围分别为0.49—0.69、0.42—0.54,S/D范围为2.28—2.83、1.75—2.12。同一温度下栉孔扇贝的HR、ABF、PS、ED指标水平均高于虾夷扇贝,Max-IBF、Min-IBF水平均低于虾夷扇贝;两种扇贝RI和S/D指标均在一定范围内波动。研究显示,虾夷扇贝在较低的心脏和血流搏动节律下保持了高效的血液流通,从而以相对较少的能量消耗维持了其机体代谢对血液循环的需求,这也与其冷水性的生态习性相适应。     

Three dimensional seismic studies of deep-water hazard-related features on the northern slope of South China Sea

Mass transport deposits and geological features related to fluid flow such as gas chimneys, mud diapirs and volcanos, pockmarks and gas hydrates are pervasive on the canyon dominated northern slope of the Pearl River Mouth basin of the South China Sea. These deposits and structures are linked to serious geohazards and are considered risk factors for seabed installations. Based on high resolution three dimensional seismic surveys, seismic characteristics, distributions and origins of these features are analyzed. A distribution map is presented and geometrical parameters and spatial distribution patterns are summarized. Results show that various groups of the mapped features are closely tied to local or regional tectonism and sedimentary processes. Mass transport complexes are classified as slides near the shelf break, initially deformed slumps on the flanks of canyons and highly deformed slumps on the lower slope downslope of the mouth of canyons. We propose them to be preconditioned by pore pressure changes related to sea level fluctuations, steep topography, and fluid and fault activities. Gas chimneys are mainly located in the vicinity of gas reservoirs, while bottom-simulating reflectors are observed within the gas chimney regions, suggesting gas chimneys serve as conduits for thermogenic gas. Mud diapirs/volcanos and pockmarks are observed in small numbers and the formation of pockmarks is related to underlying gas chimneys and faults. This study aims at reducing risks for deep-water engineering on the northern slope of South China Sea.     

Fracture characteristics in Cretaceous platform and overlying ramp carbonates: An outcrop study from Maiella Mountain (central Italy)

This article focuses on field- and laboratory-based characterization of vertically persistent fractures that are part of oblique-slip normal fault zones and crosscut the Cretaceous platform and overlaying ramp carbonates outcropping at Maiella Mountain (central Italy). The achieved results show that: (i) fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones; (ii) joints and sheared joints composing the fault damage zones are taller, better connected and less spaced within the former rocks than in the ramp carbonates. The aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure. At Maiella Mountain, platform carbonates are, indeed, made up of overall stiffer (higher Uniaxial Compressive Strength values) and less porous rocks, due to more abundant intergranular void-filling cement and presence of matrix.In terms of hydrocarbon flow and recovery, geometric and dimensional attributes of fractures suggest that the well-connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow. In contrast, the relatively poorly connected and low-density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons.     

Numerical Investigation of Submarine Hydrodynamics and Flow Field in Steady Turn

This paper presents numerical simulations of viscous flow past a submarine model in steady turn by solving the Reynolds-Averaged Navier?Stokes Equations (RANSE) for incompressible, steady flows. The rotating coordinate system was adopted to deal with the rotation problem. The Coriolis force and centrifugal force due to the computation in a body-fixed rotating frame of reference were treated explicitly and added to momentum equations as source terms. Furthermore, velocities of entrances were coded to give the correct magnitude and direction needed. Two turbulence closure models (TCMs), the RNG model with wall functions and curvature correction and the Shear Stress Transport (SST) model without the use of wall functions, but with curvature correction and low-Re correction were introduced, respectively. Take DARPA SUBOFF model as the test case, a series of drift angle varying between 0° and 16° at a Reynolds number of 6.53×106 undergoing rotating arm test simulations were conducted. The computed forces and moment as a function of drift angle during the steady turn are mostly in close agreement with available experimental data. Though the difference between the pressure coefficients around the hull form was observed, they always show the same trend. It was demonstrated that using sufficiently fine grids and advanced turbulence models will lead to accurate prediction of the flow field as well as the forces and moments on the hull.     

Snow disaster characteristics in Palongzangbu River Basin and mitigation countermeasures for road engineering

The Palongzangbu River Basin contains the highest number of maritime province glaciers in China.There are 130 glacial lakes,64 snow avalanche sites and 28 glacial debris flow gullies distributed within the basin.Snow disasters play a controlling role in the Sichuan-Tibet Highway construction,due to the terrain's special characteristics of high altitude and large height differential.Segmentation mitigation countermeasures for the Sichuan-Tibet Highway are presented based on snow disaster severity level and damage mode of the road.In the Ranwu to Midui section,snow avalanches are regional disasters, so the line should be placed in sunny slopes.In the Midui Gully to Yupu section,the line should be placed in shady slopes and at higher elevations to reduce the risk of glacial lake outburst.In the Yupu to Guxiang section,all three snow disasters are minimal.In the Guxiang to Tongmai section,glacier debris flows are the major threat,thus the road should be placed in shady slopes.     

脐带缆在潜器下放过程中的运动建模与仿真

潜器在下放布置过程中需要考虑变长度的脐带缆对其运动的影响,在考虑流的情况下,对脐带缆的有限差分模型进行了改进,并采用最小二乘方法求解由时间和空间上的中心差分格式离散后的非线性方程组。为了验证模型改进的有效性,将潜器在均匀定常流中水平匀速直航时的数值解与该特殊情况下的解析解进行比较,两组解的吻合不仅证实了模型改进的有效性,而且表明上述数值计算方法是可靠且有效的。在潜器下放布置运动给定的情况下,脐带缆的运动仿真结果表明,潜器姿态角的调整会对拖曳点处的缆绳张力大小和变化趋势产生显著的影响,流在改变缆绳空间形状的同时引起了缆绳对潜器作用力和力矩的非线性和时变性,脐带缆总是阻止潜器自身动力对运动速度和姿态角的改变,且对纵荡运动的影响最大。     

鄂尔多斯盆地南部地区延长组深水沉积构造特征及地质意义

鄂尔多斯盆地南部地区上三叠统延长组长7段发育有典型的重力流沉积。对野外露头剖面进行大量调查研究,发现研究区重力流沉积发育丰富的沉积构造,底层面构造、软沉积变形构造是主要的两种类型。这种深水沉积构造组合能够很好地揭示研究区广泛发育的一定坡度背景下深水重力流沉积体系。滑移-滑塌沉积、砂质碎屑流沉积、浊流沉积是研究区发育最为广泛的深水重力流沉积类型,滑移-滑塌及软沉积变形构造为触发机制沉积响应,底层面构造为砂质碎屑流沉积及浊流沉积响应。综合分析研究区地层发育的大量凝灰岩夹层、深水泥岩中发育的植物碎屑、深水砂岩中发育的大量浅黄色泥砾等沉积特征,认为地震、火山喷发及季节性洪水为研究区深水重力流沉积最有利的触发因素。