海流作用下海底管道溢油扩散实验研究

采用物理模型试验研究了海流作用下海底输油管道溢油扩散特性。水槽中的原油从管道的泄漏点溢出,并从海底扩散到海面。采用非接触式光学测量技术,设计了图像采集与数据分析系统,研究原油泄漏机理和特性。通过该系统获得了溢油的轨迹、速度和海面上升时间。从定性和定量两个角度分析了水流和溢油量对溢油行为的影响。之后给出了特征物理量对各种因素的敏感性研究。溢油在水下主要以不同粒径的散状颗粒的形式分布。原油的上升过程可分为三个阶段：饱满、分散和聚集阶段。溢油量是影响油粒子上升时间的主要因素。在油粒子的上升过程中,原油的垂直速度主要受溢油量的影响,横向速度则更依赖于水流速度。不同水流与溢油量下,横向溢油速度的偏差远大于海面上升时间和垂直溢油速度的偏差。该研究可为溢油应急预测系统提供理论参考。     

浅海地转流速的计算

地转流是海洋中的一种基本流动。准确地计算和预报海洋中的地转流速,对于国防军事、航海运输以及渔业生产等方面都具有极其重要的实践意义。因此,各国海洋科学工作者,历来对地转流速的计算极为重视。本世纪初, Sandst?m 及 Helland-Hansen根据Bjerknes的环流理论,于1903年首次发表了应用温、盐度资料计算地转流速的著名的“Helland- Hansen公式”,即海流的“动力计算方法”。这是海流计算上的重要贡献之一。对深海大洋来说,通过选取“动力零面”的办法。可以得到地转流的绝对流速。如果“动力零面”选取得当,应用“动力计算方法”得到的绝对流速与实测流速极为接近。但在浅海中广泛应用这种“动力计算方法",显然遇到了不少困难。其中关于浅海“动力零面”"的恰当选取以及如何处理由于海底深度不等所引起的影响,是最为重要的两个间题。为了解决这些问题,国外的海洋科学工作者,如Helland-Hansen(1934,转引自 Φомин,1964), COMOB(1937,转引自3yσoB及Mamaeb,1956;,下称3aσon方法),斯费德鲁普等(1946)和Grcen(1948)等,都对此进行了研究,并提出过各自的“浅海动力计算方法”。总起来看这些方法,都假定海底以下的泥土岩石层中(以下通称“假想水体")某一水平面(一般取通过海底最深点)为“动力零面”作为地转流速计算的起点。对于海底及海底以下的“假想水体”中的海水比容分布。却有着几种不同的设想和处理方法。大体可分为两类:第一类(如Helland- Hansen,3yσoB等)是假定海底及其“假想水体”中流速和水平压强梯度同时消失,即那里的等比容线呈水平分布,从而采用线性内插的处理方法去确定其比容分布;第二类(如Sverdrup, Groen等)则假定海底及其“假想水体”中水平压强梯度并未消失,即那里的等比容线不,呈水平分布,从而采用灵活性和随机性较大的非线性内插的处理方法去确定其比容分布。 但迄今为止,这些研究尚未能得出令人满意的结果。我国近海是广阔的大陆架浅海,并且陆架和陆坡毗连区域的海底坡度变化很大,因此研究“动力计算方法”在浅海应用中所存在的这些问题,一直是我国近海海流研究工作中一项迫切的任务。 无产阶级文化大革命前,我们曾经分别采用过“3yσoB方法”和“Groen方法”,计算了我国近海的地转流速。实践证明,这两种“浅海动力计算方法”,还存在着不少问题;特别对海底地形变化剧烈的海区,尤为突出,其计算结果和客观实际相差甚远。针对这些问题,我们初步进行了一些探讨,提出了本文所要介绍的“浅海地转流速的计算”方法。 国外现有的“浅海动力计算方法”中的一个主要问题,是把海底以下的泥土或岩石当作水体(即“假想水体”)来处理。从而引进所谓浅海动力计算中的“订正项”(通过“假想水体”对“真实水体”予以订正)。我们认为计算浅海海水质点的运动速度,不是把基点放在真实的海水中,而是人为地放在海底以下的泥土或岩石中;这种处理方法,可能有一定的主观性。由此而确定的“订正项”也就缺乏足够的客观依据。本文将摈弃国外在“浅海动力计算方法”中迄今所采用的所谓“假想水体”,直接通过真实海水中海水密度水平梯度的差分近似计算:;在不引进任何人为的“订正项”的情况下,去确定浅海地转流速。实例计算结果表明,应用本文所提出的通过密度水平梯度去计算浅海地转流速的计算方法,比国外现有的“浅海动力计算方法”有较高的精度。     

Intensification of nonlinear wind waves on clean water and in the presence of an oil film

The intensification of gentle plane waves at the initial stage of their generation by a steady wind flow in a laboratory setup is investigated. It is found that the wave form is changed by eddies that are formed in the viscous layer of a steady air flow on the leeward slope: the water surface rises under the action of eddies to form a complexly shaped slope. Calculated and measured data for gentle nonlinear waves on clean water are in good compliance with each other. It is shown that, in the presence of an oil film, the region of eddy separation encompasses the wave trough as well, because oil flows down and the film is thickened in passing from the slope to the trough. The water-surface rise by eddies in the trough restricts an increase in the amplitude and steepness of the wave.     

N,N-二烷基酰胺类物质的膜状态及其在水面溢油集油剂中的应用研究

合成了 5种 N,N-二烷基酰胺型表面活性剂 ,并对其所成膜的状态进行了测定。表明当N,N-二烷基酰胺类物质单独成膜时获得的集油膜为多层膜 ,而当选用合适的溶剂与其配制成溶液以后 ,所成的集油膜则为转变膜或液态凝聚膜。在 5种 N,N-二烷基酰胺类物质中 ,酰基碳链越长、氮烷基碳链越短则其集油能力越强。应用 N,N-二烷基酰胺类物质配制了 4个配方 ,均具备良好的集油能力 ,并且对原油的集油能力大于对柴油的集油能力     

深海悬垂取水管振动特性研究

深海悬垂取水管的设计趋向于大直径、高内流流速,内流对取水管振动特性的影响不可忽略,分析内部流动引起的管道动态失稳行为以及评估失稳临界流速具有重要工程意义。基于小尺度模型试验,研究内流对深海悬垂取水管道振动特性的影响规律,结果表明：随着内流流速增加,取水管模型会发生动态失稳行为,表现为一种间歇性的近周期运动,该运动主要由管道一阶弯曲模态引起的不稳定性诱导。管道材料、顶端连接方式及底部配重块均影响其动态稳定性,顶端固定连接时质量比小的管道更易发生动态失稳;顶端变为铰接时,质量比大的管道失稳临界流速变小,质量比小的管道失稳临界流速变大。相比顶端边界条件,底部配重块对管道失稳临界流速影响不显著但可以减小其振动幅值。     

Numerical Study on the Vertical Water Exit of A Cylinder with Cavity

When a high-speed body with cavity passes through water-air free surface and exits water, its mechanical environment and dynamic characteristics change significantly due to the great difference in density and viscosity between water and air. With focusing on this problem, the Computational Fluid Dynamics (CFD) method is applied to perform numerical calculation on the process of this vapor-liquid-gas flow during the water exit of a high-speed cylinder, with the Volume of Fraction (VOF) multiphase flow interface-capturing techniques and the overset grid technology. After the verification and validation of the CFD model through mesh convergence study and a water-entry experiment, cavity evolution and flow characteristics including pressure and velocity distribution during the water exit are analyzed. The effects of different initial velocities on the pressure distribution and drag characteristics of the cylinder are investigated. Calculated results show that the cavity collapse during water exit causes strong pressure fluctuation on the cylinder; when the cylinder exits water enveloped in a supercavity, the pressure distribution on its wall surface and surrounding water region is relatively uniform, and the drag changes gently, and thus the cylinder has good motion stability.

     

聚丙烯-分子筛测油法的研究

聚丙烯纤维是一种良好的吸油材料。它具有吸油率高和吸油速度快的优点。将它装入油膜采集器,可以吸收漂浮于水面上的同面积的油膜。聚丙烯纤维在吸油的同时,也能吸收一部分水,用3A型的分子筛将水吸出,即可得到吸收的油重。用该方法可以较准确地测定漂浮于水面上的油膜重量和厚度。     

Hydrodynamics of oil jets without and with dispersant: Experimental and numerical characterization

In this paper, we present the analysis of an underwater horizontal oil jet experimental measurement and Computational Fluid Dynamics (CFD) using the Reynolds Averaged Navier Stokes (RANS) equations. Two oil subsurface releases were conducted: one with crude oil and another with crude oil premixed with dispersant at the dispersant to oil ratio (DOR) of 1:20. The jet profile was captured by a camera at moderate resolution, and the instantaneous velocity was measured by a Vectrino Profiler. The velocity components, turbulence kinetic energy, and turbulence dissipation rate from the experiment agreed well with those from the CFD simulation using the k-epsilon turbulence model. The spread angle of the jet was found to be around 21° and 24° from the experiment measurement, for oil without dispersant and oil with dispersant, respectively. The latter is close to the angle of miscible jets at 23°. The jet profile of oil with dispersant had a smaller buoyancy than that without dispersant, which is probably due to the large water entrainment for the oil with dispersant jet. The cross sections of the jet for both cases gradually became flattened with distance, as the plume turned upward.     

Effects of Topography and Current on Horizontal Irrotational Waves in Shallow Water

Based on the Boussinesq assumption,derived are couple equations of free surface elevationand horizontal velocities for horizontal irrotational flow,and analytical expressions of the correspondingpressure and vertical velocity.After the free surface elevation and horizontal velocity at a certain depth areobtained by numerical method,the pressure and vertical velocity distributions can be obtained by simplecalculation.The dispersion at different depths is the same at the O(ε)approximation.The waveamplitude will decrease with increasing time due to viscosity,but it will increase due to the matching ofviscosity and the bed slope.thus,flow is unstable.Numerical or analytical results show that the waveamplitude.velocity and length will increase as the current increases along the wave direction.but theamplitude will increase.and the wave velocity and length will decrease as the water depth decreases.     

Nonlinear output feedback control of underwater vehicle propellersusing feedback form estimated axial flow velocity

Accurate propeller shaft speed controllers can be designed by using nonlinear control theory and feedback from the axial water velocity in the propeller disc. In this paper, an output feedback controller is derived, reconstructing the axial flow velocity from vehicle speed measurements, using a three-state model of propeller shaft speed, forward (surge) speed of the vehicle, and the axial flow velocity. Lyapunov stability theory is used to prove that a nonlinear observer combined with an output feedback integral controller provide exponential stability. The output feedback controller compensates for variations in thrust due to time variations in advance speed. This is a major problem when applying conventional vehicle-propeller control systems. The proposed controller is simulated for an underwater vehicle equipped with a single propeller. The simulations demonstrate that the axial water velocity can be estimated with good accuracy. In addition, the output feedback integral controller shows superior performance and robustness compared to a conventional shaft speed controller     

Numerical simulation of oblique water entry of an asymmetrical wedge

The hydrodynamic problem of a two-dimensional asymmetrical wedge entering calm water obliquely at constant speed is analyzed based on the velocity potential theory. The gravity effect on the flow is ignored based on the assumption that the ratio of the entry speed to the acceleration due to gravity is much larger than the time scale of interest. The problem of this similarity flow is solved by a boundary element method together with an analytical solution for the jet based on the shallow water approximation. Various results are provided for the wave elevation, pressure distribution and force at different deadrise angles and at different oblique entry. The effects of asymmetry and horizontal speed on these results are investigated.     

均匀剪切流场中的强非线性波及其色散关系

考虑了剪切流场中强非线性波,唯一的假设是水深与特征波长之比是小量,建立了基于任意水深处速度而不是通常所用的平均速度为速度变量的模型。不仅改进了色散关系,使模型的水深适用范围更大,而且由于整个推导过程对波的振幅没有做任何假设,因而所获得的模型可以用于任何振幅的波。     

释放角对水下溢油的羽流动力学特性的影响

在考虑羽流阻力的情况下,采用拉格朗日控制单元积分法建立了羽流动力学模型,并采用数值技术对水下溢油羽流动力学特性进行了模拟,详细分析了释放角对羽流运动的影响。模拟结果及分析表明,当释放方向不同时,浮力在羽流轴线上的投影分量不同。在不同的浮力分量作用下,羽流的运动轨迹及羽流速度、浓度和半径随着流程的变化会呈现不同的特点。羽流的这些运动特点可能会使得溢油到达水面的时间及位置随释放角的不同而发生变化。     

海面水包油乳化液溢油量等效估算方法研究

激光诱导荧光(LIF)是一种主动光学探测技术,该技术已在海面未乳化溢油油种鉴别及油膜厚度评估方面取得了一定的研究成果,但乳化溢油的监测理论基础和探测方法尚未成熟。溢油乳化物的量化会直接影响溢油污染的应急处理和灾害评估,但目前对溢油乳化液溢油量的计算尚未有研究报道。本文以水包油乳化液为研究对象,基于等效思想,根据油量相等建立了水包油乳化液与油膜的荧光检测等效模型,并依据光的辐射传输机理推导出等效油膜厚度的估算公式,最后采用仿真实例对估算方法的适用性和有效性进行了验证。实验结果表明,当水包油乳化液含油率小于12×10^-6,厚度小于5.98 cm时,利用所提出的等效方法能有效计算出水包油实际溢油厚度。该方法可为海面乳化溢油量的估算提供一种创新性的方法,具有良好的借鉴意义和实际应用价值。     

水平螺旋槽微肋管壁面升膜流动特性的研究

对蒸发状态下水平螺旋槽微肋管管外壁面升膜的形成机理和流动特性进行研究。对驱动液膜形成的润湿力进行分析,建立单组分流体的数学模型,得出壁面液膜蒸发时的速度和厚度分布,并对影响水平螺旋槽微肋管升膜的流动特性的因素进行分析,得出水平螺旋槽微肋管更有益于形成连续均匀的液膜,有更好的流动特性,增强传热传质效果。     

海底峡谷内浊流流动与沉积特征数值模拟研究

数值模拟已成为研究海底浊流的重要方式,开展海底浊流的流动与沉积特征的数值模拟,对深水沉积体系特征研究、海底工程设施稳定性评价以及深海油气勘探均具有重要意义。本文基于不可压缩流体Navier-Stokes方程与湍流k-ε模型构建了浊流数值计算模型,设定不同粒径、速度与悬浮颗粒物浓度等初始条件,模拟并分析了单粒径悬浮颗粒驱动的持续入流的海底浊流沿海底连续坡折带的流动过程及沉积特征。模拟结果显示,浊流在斜坡段处于加速状态,水平段流速骤减并逐渐沉积,且浊流在小坡度的加速不改变浊流的沉积趋势。浊流由于环境水体的夹带效应逐渐增厚,且浊流头部形态与流动特征与实测资料吻合良好。本文另对多频次持续入流浊流进行了模拟,并将模拟结果与实测地层沉积特征对比,结果显示,多频次持续入流的海底浊流在纵向上可能会形成多个不连续鲍玛层序的叠积。     

一种水驱剩余油物模实验相似转化方法数模验证

在水驱剩余油物理模拟实验研究中,目前提出了一种新的相似转化方法,即通过运动速度（渗流真实速度）相等求取的物模实验排量,在岩心物性、流体性质相似,几何尺寸成比例的不同物理模型中驱替,其剩余油分布规律及开采效果相似,该规律是文中相似方法的核心规律,它可以有效地应用到室内物理模型实验对矿场剩余油分布规律的研究中去.此文重点考虑了重力、毛管力对运动速度相似转化方法的影响与修正,并设计了20余套数值模拟方案,验证了这种方法的准确性及实用性.     

油气混输系统的实验研究与实验模拟准则

描述了油气混输系统的实验研究,特别是多相流的流态、增压、计量系统的实验研究,并用动力相似理论分析了油气混输两相管流实验模拟所需满足的相似参数,提出了各种简化条件下的相似规律,讨论了用水和空气的两相流动来模拟原油和天然气的两相流动的可靠性和提高实验精度的手段和方法。     

溢油乳化过程C波段微波散射特性实验研究

本文基于水槽溢油观测实验,研究溢油乳化过程中表面散射特性的变化。利用全极化C波段微波散射计和矢量网络分析仪等测量设备对易发生乳化反应沥青含量小于3%的原油（A型油）、油田中开采出的新鲜原油（B型油）和经过脱水去杂质处理的工业原油（C型油）进行观测。文中详细分析了在C波段微波下乳化油膜与平静水面的后向散射差异,以及油膜乳化过程对后向散射的影响,结果显示在低风速、无浪的条件下（最大波高低于3mm）,原油的乳化反应可通过表面粗糙度和自身介电常数的变化来调制雷达后向散射,并且这两种方式中表面粗糙度的影响占主导地位。对比B型和C型原油在乳化状态和未乳化状态下的表面后向散射,结果显示在各状态下B型油膜表面后向散射均大于C型油,且在VV、HH、HV/VH极化方式下两者后向散射平均差异分别为2.19 dB、2.63 dB、2.21 dB,在20%油膜含水率的乳化状态下差异较未乳化状态时小,平均差异分别为0.98 dB、1.49 dB、1.5 dB,结果表明不同类型油种间由于成分和油膜属性的不同会在一定程度上导致油膜表面粗糙度存在差异,影响油膜表面后向散射。