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1.
在海洋油气开发中,水下节流阀作为水下生产系统的重要组成部分,用于调节生产单元的流量,冲蚀是其主要失效因素之一,因此研究水下节流阀冲蚀失效的影响机理尤为重要。以某笼套式角型水下节流阀为研究对象,建立了水下节流阀的三维流体域模型,采用ANSYS Fluent的标准k-ε湍流模型、DPM离散相模型和Generic冲蚀模型进行了不同开度下的流场数值模拟计算和冲蚀分析,研究了流场环境参数对冲蚀的影响。对水下节流阀流场数值模拟结果进行分析,得到了水下节流阀流场内流速、压力的分布规律。对不同开度下水下节流阀的冲蚀数值模拟结果进行分析,发现节流孔处是冲蚀最为严重区域,得到了冲蚀率随开度的变化曲线。对不同流场环境参数下水下节流阀的冲蚀数值模拟结果进行分析,得到了最大冲蚀率和最大冲蚀深度随流场环境参数的变化规律。根据数值模拟的分析及结论可以对水下节流阀结构进行改进,并在油气生产中对流场环境参数进行控制,提高海洋油气开发的经济效益。 相似文献
2.
内孤立波具有振幅尺度大、能量集中的特点,其引起流场和密度场的迅速变化可能对海洋工程结构物以及水下潜体造成严重威胁。因此研究不同造波条件下生成的内孤立波运动的流场特征具有重要的学术意义和实际应用价值。采用直接数值模拟方法和给定的初始密度场密度跃迁函数,对重力塌陷激发内孤立波的运动过程进行研究,探讨了不同造波条件下,激发产生的内孤立波波型、涡度、振幅和水平速度等流场特征。结果表明:(1)直接模拟数值方法能够模拟内孤立波传播过程中的密度界面波型反转现象;(2)从定性和定量的角度,证实了不稳定内孤立波传播过程中存在能量的向后传递;(3)对于相同的台阶深度(水闸两侧初始密度界面的高度差),初始涡流保持相同,但是随着上下层水深比的减小,其强度下降显著;(4)台阶深度对初始涡流的垂直结构的影响要大于上下层水深比,且台阶深度对内孤立波的振幅、水平速度的影响显著。 相似文献
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4.
基于自编程序发展了一种平板近壁面通气气液两相湍流流动数值模拟方法,并对近壁面双孔通气气液两相流场进行了数值模拟分析。研究结果表明：建立的数值计算方法摆脱了对传统 RANS 湍流模型的依赖, 可以较好地捕捉气液界面的失稳现象,模拟结果与实验结果吻合较好。平板近壁面双孔通气气泡的掺混融合过程可以分为 3 个流动阶段：独立稳定发展阶段、初步掺混融合阶段以及充分融合阶段。流场中气泡的发展演化与旋涡结构相关,剪切层涡和反向旋转涡对在其掺混融合过程中起着主要作用。 相似文献
5.
盐指现象的数值模拟研究对理解小尺度海洋动力学过程具有十分重要的意义。本文建立了二维方腔模型,通过有限体积法求解控制方程,对盐指现象的演化过程进行了模拟计算和数值分析,在热瑞利数为(1.12～2.24)×107的变化范围内,展示并对比了不同粘滞系数、热瑞利数和盐瑞利数情况下的盐指现象,发现随着粘滞系数的增加,盐指的演变速率变慢,生成数目减少;热瑞利数的增加对盐指的演变速率具有抑制作用,而盐瑞利数的增加则对其具有促进作用。 相似文献
6.
台风"森拉克"的数值模拟研究:海洋飞沫的作用 总被引：7，自引：0，他引：7
台风作为一种在海洋上生成和演变的强烈天气现象，除了环境流场、自身结构以及地形等因子对它产生影响外，海气间的热量动量交换也是台风演变过程中不可或缺的因子。台风期间在海气界面生成大量海洋飞沫，这些飞沫在台风边界层的蒸发必然对海气之间的通量传输过程产生影响，进而影响到台风本身的演变。文章将海洋飞沫参数化引入大气中尺度模式中，对2002年16号台风“森拉克”的演变进行了数值模拟研究。结果表明，引入海洋飞沫参数化方案，可使台风期间海气界面的潜热通量增加50％，10m层风速最大值增加30％，从而使模拟台风的强度明显增加，使模拟结果更趋于合理。因此，在台风数值模拟和预报中考虑海洋飞沫的作用是十分必要的。 相似文献
7.
水下溢油数值模拟研究 总被引：1，自引：0，他引：1
基于Lagrange积分法和Lagrange粒子追踪法建立了一个水下溢油数值模型。该溢油模型由两个子模型组成:羽流动力模型和对流扩散模型,其中羽流动力模型用以模拟溢油的喷发阶段和浮力羽流阶段;对流扩散模型用以模拟溢油的对流扩散阶段。通过数值实验,结合实验室水槽实验和水下溢油现场实验的观测资料进行模型验证。实验结果表明,模拟结果与观测资料一致性较好,从而验证了本文溢油模型的合理性和准确性;羽流动力模型为对流扩散模型提供源,海流、海水的垂向密度结构和油滴的直径分布是影响溢油在对流扩散阶段运动和分布的主要因素。 相似文献
8.
海洋溢油溯源数值模拟可以为海上溢油事故的应急处置提供技术支撑,同时对确定溢油事故的泄漏源和责任方也具有重要的指导意义。本文概述了海洋溢油溯源数值模拟方法的最新研究成果,总结分析了包括对流扩散过程的逆运算、受体模式、粒子追踪模式和垂向溯源方法等在内的四类数值模拟方法的基础理论和研究进展。同时,归纳了三种常用的溢油溯源数值模拟结果分析方法,并给出了每种方法的优缺点及其对应的适用条件。在分析海洋溢油溯源数值模拟方法应用现状的基础上,初步探讨面临的挑战。这对全面理解溢油溯源数值模拟方法的理论和应用提供了重要参考,并可为相关工作和后续数值模拟方法的改进奠定基础。 相似文献
9.
我国是依据法制管理疏浚物海洋倾废的国家。几年来,疏浚物海洋倾废研究也相应发展到一定水平。实践经验和理论研究表明:从疏浚物排海时刻起到污染物的最后归宿止,它所经历的物理、化学、生物过程是十分复杂的过程。其中,物理过程是最基本的过程,亦即海洋自净研究的核心内容是其沉降、扩散和输运。因此,本文旨在对疏浚物海洋倾废研究现状进行概述,内容涉及基线研究,环境质量现状评价,疏浚物沉降过程实验和数值分析,声学追踪试验,同位素技术应用,流场数值分析,标识质点漂移数值跟踪试验,抛泥运移数值模拟以及环境影响预测等。最后介绍一种“疏浚物倾倒区选划模式”并对今后疏浚物海洋倾废研究提出一点建议供参考。 相似文献
10.
内孤立波对海洋平台的安全运行存在一定的威胁,基于三维数值水槽对内孤立波传播引起的半潜平台受力及其周围流场的分布进行了数值模拟研究.通过与试验对比,分析了入射波幅和分层流体深度比对半潜平台上内孤立波荷载特性的影响规律,验证了数值模拟结果是准确可靠的.研究表明,内孤立波引起的平台荷载会随着内孤立波波幅的增加而增大,随着分层流体深度比的增加而减小.基于对平台周围剖面速度场和三维涡场的演化规律研究,发现在内孤立波传播过程中,平台周围会出现明显的速度减小区,平台周围会有大量的漩涡产生并发生脱落现象. 相似文献
11.
北冰洋上层双扩散阶梯热通量的分析 总被引：1，自引：1，他引：0
北冰洋中,低温低盐的上层水与高温高盐的大西洋水之间,广泛存在着稳定的双扩散阶梯。基于锚定剖面仪、冰基剖面仪和微结构剖面仪的数据,对温盐廓线中的阶梯进行研究,分析阶梯的热通量。固定跟踪了锚定剖面仪的3个阶梯,研究阶梯参数随时间的变化。发现由经验公式得出的上下两界面的热通量差,与混合层内热量的变化有较好的相关性。利用微结构剖面仪数据,计算阶梯界面通过分子热传导输送的热通量。当选取最大位温梯度时,算出的传导热通量与经验公式算出的热通量接近。因此,实验室研究得到的热通量经验公式,可以用于计算北冰洋双扩散阶梯的热通量。 相似文献
12.
加拿大海盆深层双扩散对流的观测分析 总被引：1，自引：0，他引：1
The Canada Basin(CB) is the largest sub-basin in the Arctic, with the deepest abyssal plain of 3 850 m. The double-diffusive process is the possible passage through which the geothermal energy affects the above isolated deep waters. With the temperature-salinity-pressure observations in 2003, 500-m-thick transition layers and lower1 000-m-thick bottom homogenous layers were found below 2 400 m in the central deep CB. Staircases with downward-increasing temperature and salinity are prominent in the transition layers, suggesting the doublediffusive convection in deep CB. The interface of the stairs is about 10 m thick with 0.001–0.002°C temperature difference, while the thicknesses of the homogenous layers in the steps decrease upward from about 60 to 20 m.The density ratio in the deep central CB is generally smaller than 2, indicating stronger double-diffusive convection than that in the upper ocean of 200–400 m. The heat flux through the deepest staircases in the deep CB varies between 0.014 and 0.031 W/m2, which is one-two orders smaller than the upper double-diffusive heat flux,but comparable to the estimates of geothermal heat flux. 相似文献
13.
加拿大海盆东南部锚定观测双扩散阶梯的时间演化研究 总被引：1，自引：1，他引：0
加拿大海盆上层,分布着高温高盐的大西洋水和相对低温低盐的盐跃层下部水,两水团之间形成一系列的双扩散阶梯。通过分析2005年8月-2011年8月期间的锚定潜标数据,对双扩散阶梯和这两种水团之间的相互作用进行研究。基于固定盐度范围的方法,在盐度廓线中识别阶梯结构,在盐度34.45~34.83范围内,获取18个阶梯结构,并研究阶梯的参数。发现双扩散阶梯的位温主要受与其接近的水团的影响,同时也受其相邻的阶梯生成或消亡的影响,大西洋水对其上方的双扩散阶梯和盐跃层下部水起到加热作用;而盐跃层下部水的深度变化主导着大西洋水和双扩散阶梯的深度变化。两个相邻的阶梯具有一致的位温和深度变化趋势。通过经验公式,估计大西洋水通过双扩散阶梯向上传输的热通量为0.05~0.6 W/m2,且由下至上呈现逐渐增大的趋势。最后,估算由双扩散造成的垂向涡扩散系数为3×10-6~3.3×10-5 m2/s,且由下至上呈现逐渐减小的趋势。 相似文献
14.
The physical processes responsible for the formation in a large‐scale ice–ocean model of an offshore polynya near the Greenwich meridian in the Southern Ocean are analysed. In this area, the brine release during ice formation in autumn is sufficient to destabilise the water column and trigger convection. This incorporates relatively warm water into the surface layer which, in a first step, slows down ice formation. In a second step, it gives rise to ice melting until the total disappearance of the ice at the end of September. Two elements are crucial for the polynya opening. The first one is a strong ice‐transport divergence in fall induced by south‐easterly winds, which enhances the amount of local ice formation and thus of brine release. The second is an inflow of relatively warm water at depth originating from the Antarctic Circumpolar Current, that sustains the intense vertical heat flux in the ocean during convection. The simulated polynya occurs in a region where such features have been frequently observed. Nevertheless, the model polynya is too wide and persistent. In addition, it develops each year, contrary to observations. The use of a climatological forcing with no interannual variability is the major cause of these deficiencies, the simulated too low density in the deep Southern Ocean and the coarse resolution of the model playing also a role. A passive tracer released in the polynya area indicates that the water mass produced there contributes significantly to the renewal of deep water in the Weddell Gyre and that it is a major component of the Antarctic Bottom Water (AABW) inflow into the model Atlantic. 相似文献
15.
This paper concerns mathematical modeling of the processes of false bottom evolution taking into account water freezing in
the opposite direction from the cooled boundary with the atmosphere. The model of the crystallization process is based on
the two-phase zone theory complicated by the moving boundaries of phase transitions and turbulent flows of fluid in the ocean
near the false bottom boundary. Analytical solutions of the nonlinear problem are found (the distributions of the temperature
and the salinity, the proportion of the solid fraction, the laws of the motion of the boundaries between the phase transitions,
and the heat fluxes) and a comparative analysis of the results with the field data observations is performed. It is shown
that the heat flux caused by the growing false bottom makes a significant contribution to the heat exchange processes between
the ocean and the atmosphere. 相似文献
16.
The sensitivity of the North Atlantic gyre circulation to high latitude buoyancy forcing is explored in a global, non-eddy resolving ocean general circulation model. Increased buoyancy forcing strengthens the deep western boundary current, the northern recirculation gyre, and the North Atlantic Current, which leads to a more realistic Gulf Stream path. High latitude density fluxes and surface water mass transformation are strongly dependent on the choice of sea ice and salinity restoring boundary conditions. Coupling the ocean model to a prognostic sea ice model results in much greater buoyancy loss in the Labrador Sea compared to simulations in which the ocean is forced by prescribed sea ice boundary conditions. A comparison of bulk flux forced hindcast simulations which differ only in their sea ice and salinity restoring forcings reveals the effects of a mixed thermohaline boundary condition transport feedback whereby small, positive temperature and salinity anomalies in subpolar regions are amplified when the gyre spins up as a result of increased buoyancy loss and convection. The primary buoyancy flux effects of the sea ice which cause the simulations to diverge are ice melt, which is less physical in the diagnostic sea ice model, and insulation of the ocean, which is less physical with the prognostic sea ice model. Increased salinity restoring ensures a more realistic net winter buoyancy loss in the Labrador Sea, but it is found that improvements in the Gulf Stream simulation can only be achieved with the excessive buoyancy loss associated with weak salinity restoring. 相似文献
17.
The resolution of the sea-ice component of a coarse-resolution global ocean general circulation model (GCM) has been enhanced to about 22 km in the Southern Ocean. The ocean GCM is designed for long-term integrations suitable for investigations of the deep-ocean equilibrium response to changes in southern hemisphere high-latitude processes. The space and time scales of the high-resolution sea-ice component are commensurate with those of the resolution of satellite passive-microwave sea-ice data. This provides the opportunity for a rigorous evaluation of simulated sea-ice characteristics. It is found that the satellite-derived continuous high ice concentration of the interior winter ice pack can only be captured when vertical oceanic mixing is modified in a way that less local, intermittent convection occurs. Furthermore, the width and the variability of the coastal polynyas around the Antarctic continent and its ice shelves are best captured when some form of ice-shelf melting is accounted for. The width of the wintertime ice edge is reasonably reproduced, while its variability remains underestimated, closely following the coarse-grid pattern of the ocean model due to its high dependence on ocean temperature. Additional variability besides daily winds, e.g. in form of idealized tidal currents, improves the temporal and spatial ice-edge variability, while leads in the interior ice pack become more abundant, more in line with the fine-scale satellite-derived texture. The coast- or ice-shelf line is described on the fine grid based on satellite passive-microwave data. This method requires parts of a coarse coastal ocean grid cell to be covered by an inert layer of “fast ice” or “ice shelf”. Reasonable long-term global deep-ocean properties can only be achieved when these areas are not inert, i.e. are exposed to heat flux and ice growth, or when the vertical mixing parameterization allows for excessive open-ocean convection. The model area exposed to cold high-latitude atmospheric conditions thus being most decisive for a realistic representation of the long-term deep-ocean properties, suggests that high-latitude coastlines are definitely in need of being represented at high resolution, including ice sheets and their effects on the heat and freshwater flux for the ocean. 相似文献
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19.
《Ocean Modelling》2002,4(2):137-172
A new sea ice model, GELATO, was developed at Centre National de Recherches Météorologiques (CNRM) and coupled with OPA global ocean model. The sea ice model includes elastic–viscous–plastic rheology, redistribution of ice floes of different thicknesses, and it also takes into account leads, snow cover and snow ice formation. Climatologies of atmospheric surface parameters are used to perform a 20-year global ocean–sea ice simulation, in order to compute surface heat fluxes from diagnosed sea ice or ocean surface temperature. A surface salinity restoring term is applied only to ocean grid cells with no sea ice to avoid significant surface salinity drifts, but no correction of sea surface temperature is introduced. In the Arctic the use of an ocean model substantially improves the representation of sea ice, and particularly of the ice edge in all seasons, as advection of heat and salt can be more accurately accounted for than in the case of, for example, a sea ice–ocean mixed layer model. In contrast, in the Antarctic, a region where ocean convective processes bear a much stronger influence in shaping sea ice characteristics, a better representation of convection and probably of sea ice (for example, of frazil sea ice, brine rejection) would be needed to improve the simulation of the annual cycle of the sea ice cover. The effect of the inclusion of several ice categories in the sea ice model is assessed by running a sensitivity experiment in which only one category of sea ice is considered, along with leads. In the Arctic, such an experiment clearly shows that a multicategory sea ice model better captures the position of the sea ice edge and yields much more realistic sea ice concentrations in most of the region, which is in agreement with results from Bitz et al. [J. Geophys. Res. 106 (C2) (2001) 2441–2463]. 相似文献
20.
Akio Ishida Kisaburo Nakata Shigeaki Aoki Hiroshi Kutsukake Michio J. Kishi Masahisa Kubota 《Journal of Oceanography》2001,57(4):433-450
Distributions and characteristics of water mass and chlorofluorocarbons (CFCs) in the North Pacific are investigated by using
a General Circulation Model (GCM). The anthropogenic CO2 uptake by the ocean is estimated with velocity fields derived from the GCM experiments. The sensitivity of the uptake to
different diffusion parameterizations and different surface forcing used in the GCM is investigated by conducting the three
GCM experiments; the diffusive processes are parameterized by horizontal and vertical eddy diffusion which is used in many
previous models (RUN1), parameterized by isopycnal diffusion (RUN2), and isopycnal diffusion and perpetual winter forcing
for surface temperature and salinity (RUN3). Realistic features for water masses and CFCs can be simulated by the isopycnal
diffusion models. The horizontal and vertical diffusion model fails to simulate the salinity minimum and realistic penetration
of CFCs into the ocean. The depth of the salinity minimum layer is better simulated under the winter forcing. The results
suggest that both isopycnal parameterization and winter forcing are crucial for the model water masses and CFCs simulations.
The oceanic uptake of anthropogenic CO2 in RUN3 is about 19.8 GtC in 1990, which is larger by about 10% than that in RUN1 with horizontal and vertical diffusive
parameterization. RUN3 well simulates the realistic water mass structure of the intermediate layer considered as a candidate
of oceanic sink for anthropogenic CO2. The results suggest that the previous models with horizontal and vertical diffusive parameterization may give the oceanic
uptake of anthropogenic CO2 underestimated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献