Numerical Simulation of Waves Generated by Seafloor Movements

Waves generated by vertical seafloor movements are simulated by use of a fully nonlinear two-dimensional numerical wave tank. In the souree region, the seafloor lifts to a designated height by a generation function. The numerical tests show that the linear theory is only valid for estimating the wave behaviors induced by the seafloor movements with a small amplitude, and the fully nonlinear numerical model should be adopted in the simulation of the wave generation by the large amplitude seafloor movements. Without the background surface waves, many numerical tests on the stable maximum elevations η0^max are carried out by beth the linear theory and the fully nonlinear model. The results of two models are compared and analyzed. For the fully nonlinear model, the influences of the amplitudes and the horizontal lengths on η^max are stronger than that of the characteristic duration times. Furthermore, results reveal that there are significant differences be- tween the linear theory and the fully nonlinear model. When the influences of the background surface waves are considered, the corresponding numerical analyses reveal that with the fully nonlinear model the η0^max near-linearly varies with the wave amplitudes of the surface waves, and the η0^max has significant dependences on the wave lengths and the wave phases of the surface waves. In addition, the differences between the linear theory and the fully nonlinear model are still obvious, and these differences are significantly affected by the wave parameters of the background surface waves, such as the wave amplitude, the wave length and the wave phase.

Threshold of Sediment Movement in Different Wave Boundary Layers

A review of former studies on the onset of sediment movement under wave action reveals that the Shields criterion obtained in unidirectional steady flow can also be applicable to oscillatory unsteady flow when the boundary layer is the same. In this paper, through comparison of different boundary layers in wave and steady flow conditions, a new criterion is presented which can be used to predict the threshold of sediment movement Linder wave action. The criterion curve shows good agreement with the experimental data.

The Advection Wave-in-Secondary Saturation Movement Equation and Its Application to Concentration Tension-Driven Saturation Kinetic Flow

The deterministic description of a wave of solution particle of efavirenz is given. Simulated pharmacokinetic data points from patients on efavirenz are used. The one dimensional wave equation is used to infer on transfer of vibrations due to tension between solution particles. The work investigates movement using wave analogy, but in a different variable space. Two important movement fluxes of a wave are derived an attracting one identified as tension conductivity and a dispersing one identified as tension diffusivity. The Wave Equation can be used to describe another spin-off movement flux formed induced by vibrations in solution particle.

Experimental research on unstable movements of sandbars under wave actions

This study is motivated by recognition of complex sandbar evolution patterns under wave actions inside the surf zone. A series of physical model experiments were conducted in a wave flume to investigate sandbar migration under various wave conditions, including wave groups, regular waves, and random waves. It was observed that under certain wave conditions sandbars move alternately shoreward and seaward rather than continuously in the same direction. The measurements show that the unstable movement of sandbars is closely related to the amplitude modulation of waves. Smaller amplitude modulation tends to produce more intense unstable bar movements. Data analysis further shows that the sandbar migration does not seem to be a passive response of the sea bed to wave forcing, but is most likely caused by the feedback interaction between waves and bed topography.

Research on Measurement of Bed Shear Stress Under Wave-Current Interaction

The movement of sediment in estuary and on coast is directly restricted by the bed shear stress. Therefore, the research on the basic problem of sediment movement by the bed shear stress is an important way to research the theory of sediment movement. However, there is not a measuring and computing method to measure the bed shear stress under a complicated dynamic effect like wave and current. This paper describes the measurement and test research on the bed shear stress in a long launder of direct current by the new instrument named thermal shearometer based on micro-nanotechnology. As shown by the research results, the thermal shearometer has a high response frequency and strong stability. The measured results can reflect the basic change of the bed shear stress under wave and wave-current effect, and confirm that the method of measuring bed shear stress under wave-current effect with thermal shearometer is feasible. Meanwhile, a preliminary method to compute the shear stress compounded by wave-current is put forward according to the tested and measured results, and then a reference for further study on the basic theory of sediment movement under a complicated dynamic effect is provided.

Sediment mathematical model for sand ridges and sand waves

A new theoretical model is formulated to describe internal movement mechanisms of the sand ridges and sand waves based on the momentum equation of a solid-liquid two-phase flow under a shear flow. Coupling this equation with two-dimensional shallow water equations and wave reflection-diffraction equation of mild slope, a two-dimensional coupling model is established and a validation is carried out by observed hydrogeology, tides,waves and sediment. The numerical results are compared with available observations. Satisfactory agreements are achieved. This coupling model is then applied to the Dongfang 1-1 Gas Field area to quantitatively predict the movement and evolution of submarine sand ridges and sand waves. As a result, it is found that the sand ridges and sand waves movement distance increases year by year, but the development trend is stable.

Numerical simulation of sediment lifted by waves and transported by tidal currents

The analysis of the scabed processes of a muddy coast has been described in this paper. On the basisof the basic differential equation of tidal current and sediment movement influenced by waves, a numerical simulation system for sediment lifted by waves and transported by tidal currents and scabed processes has been established by using MADI method, and applied to the sea area of Tianjin Port with good results.

Rheological fluid motion in tube by metachronal waves of cilia

This paper presents a theoretical study of a non-linear rheological fluid transport in an axisymmetric tube by cilia. An attempt has been made to explain the role of cilia motion in the transport of fluid through the ductus efferent of the male reproductive tract. The Ostwald-de Waele power-law viscous fluid is considered to represent the rheological fluid. We analyze pumping by means of a sequence of cilia beats from rowto-row of cilia in a given row of cells and from one row of cells to the next(metachronal wave movement). For this purpose, we consider the conditions that the corresponding Reynolds number is small enough for inertial effects to be negligible, and the wavelengthto-diameter ratio is large enough so that the pressure can be considered uniform over the cross section. Analyses and computations of the fluid motion reveal that the time-average flow rate depends on ε, a non-dimensional measure involving the mean radius a of the tube and the cilia length. Thus, the flow rate significantly varies with the cilia length.Moreover, the flow rate has been reported to be close to the estimated value 6 × 10ml/h for human efferent ducts if ε is near 0.4. The estimated value was suggested by Lardner and Shack(Lardner, T. J. and Shack, W. J. Cilia transport. Bulletin of Mathematical Biology, 34, 325–335(1972)) for human based on the experimental observations of flow rates in efferent ducts of other animals, e.g., rat, ram, and bull. In addition, the nature of the rheological fluid, i.e., the value of the fluid index n strongly influences various flow-governed characteristics. An interesting feature of this paper is that the pumping improves the thickening behavior for small values of ε or in free pumping(?P = 0) and pumping(?P > 0) regions.

Numerical Simulation of Wave Field at the Kemena River Mouth in Kalimantan Island

By use of the parabolic equation of numerical simulation of wave which is suitable for large-angle propagation anti Crank-Nicolson differential method, the wave field at the Kemema River mouth has been studied for analysis of sediment movement in the area. In order to reflect wave energy loss accurately, the Bretchneider-Reid formula is quoted and the friction coefficient in the formula is discussed in this paper. The calculation results indicate that the wave becomes a little damped at the mouth of Kemena River influenced by the topography and bottom friction, and the wave at the east beach is higher than that at the west beach, because the east beach extends out.

Analysis of the rising and sinking movement of the crust in Qinghai－Xizang Plateau，China

The average swelling height of Qinghai-Xizang Plateau(Tibet) is about 4.1 km.The area is about 2 300 000 km2.It is the highest and the largest plateau in the world.Mount Qomolangma,the highest peak in the world,is located in the southern fringe of the plateau,and its height is still increasing.What is the driving force for the rising of the Qinghai-Xizang plateau?How high will the plateau still rise from now on? These questions are much concerned by people.In this paper the distribution of the pressure at different depths in the region of Qinghai-Xizang Plateau are derived according to the three-dimensional structures of the S-wave velocity in the crust and upper mantle.The crust and upper mantle structures of the Qinghai-Xizang Plateau is deliberated on the basis of the distribution with a comprehensive analysis on the rock types,earthquakes and the relative crust movements.Then the two questions raised above are discussed.

Application of the Non-Local Physics in the Theory of the Matter Movement in Black Hole

The theory of the matter movement in a black hole in the frame of non-local quantum hydrodynamics (NLQHD) is considered. The theory corresponds to the limit case when the matter density tends to infinity. From calculations follow that NLQHD equations for the black hole space have the traveling wave solutions. The domain of the solution existence is limited by the event horizon where gravity tends to infinity. The simple analytical particular cases and numerical calculations are delivered.

航行面波动干扰对目标磁定位的影响

针对传统水下目标磁定位时因未考虑海平面波动造成磁场信号测量不准确进而引起磁定位误差较大的问题,通过在原有测磁深度上叠加海平面在该处的铅直位移,将叠加后的深度引入仿真模型的系数矩阵中,再利用仿真模型计算测量深度中包含海面波动的测量点处的磁场,以该磁场作为磁定位的数据源。采用三维LonguetHiggins模型描述10个组成波形成的波面运动,分析组成波中最大振幅取0.5 m和1 m两种情况。仿真结果表明,其对应的波面铅直位移在某些点处将大于2 m和4 m。船模试验证实,在不考虑舰船在海面波动下产生的纵倾横摇对磁场测量的影响的条件下,当组成波的最大振幅小于0.5 m,波面的最大铅直位移小于2 m时,海平面波动对磁定位结果的影响不大。

面向非稳态场景的生命体征监测优化方法

使用基于调频连续波的毫米波雷达监测生命体征信息,具有无接触、隐私保护性好、高分辨率以及抗干扰性好等优势,逐渐成为研究热点.然而,目前研究者主要关注如何提高被测对象处于稳态(如静止)时的体征监测效果,但受制于肢体运动对雷达信号的干扰,使得该技术在非稳态场景中的应用受到限制.提出一种基于人体运动状态识别的非稳态场景体征监测方法,以best-effort方式实现了存在大幅度肢体动作的场景中对体征信息的监测,并且能够识别对应的动作类型.首先,根据运动特征计算出带有距离-主导速度信息的特征频谱图.其次,使用一种滑动窗口采样方法以采集连续样本.随后训练ResNet-18网络来识别运动状态以及分类运动类型.最后,基于运动状态分类结果,在运动间歇期提取信号的相位信息,采用变分模态分解算法进行呼吸速率和心率的提取.实验结果表明,训练后的网络可以精确地识别运动状态和运动类型,识别准确率接近97%,识别延迟小于1.1 s.对呼吸和心率的监测结果的平均绝对误差(MAD)下降到1.7 bpm和3.4 bpm.

冷战视野下1960年美国黑人入座运动及其影响

1960年,非洲掀起民族独立浪潮,17个国家摆脱了白人的殖民统治,而自诩为“自由世界领袖”的美国,在废除种族隔离上却步履蹒跚。这种强烈的反差刺激美国黑人创新斗争方式。1960年,4名黑人大学生在北卡罗来纳州格林斯博罗市发起入座运动,抵制午餐柜台的种族隔离。该运动迅速发展到其他南部州,把斗争目标扩大到所有的公共场所。其发展规模之大、持续时间之长、席卷城市之多、涉及领域之广,远超之前的民权斗争。入座运动吸引了广大黑人和白人大学生,他们取代职业民权活动家,成为民权运动的主要参与者,并把被捕入狱的斗争经历看作是一种荣誉。入座运动推动民权运动从法庭斗争转向大规模非暴力直接行动。它重塑了民权运动,标志着民权运动高潮的到来。

规则波与浮式防波堤相互作用的SPH模拟研究

相较于传统防波堤,浮式防波堤因具有方便安装、可实现水质交换、可在多种环境下施工以及可移动等优点得到了广泛发展。采用光滑粒子流体动力学(SPH)方法,研究规则波与浮式防波堤的相互作用。首先在空水槽中基于规则波传播算例进行粒子间距的收敛性分析,然后基于验证的水槽模型模拟规则波与单浮体、双浮体的相互作用,并分析了浮体前后波形、浮体的运动及浮体附近的流速场。结果表明,双浮体防波堤相比单浮体防波堤能够显著提升消波性能。

洗涤条件和织物运动对纤维微塑料释放的影响

为研究不同洗涤条件和织物运动状态对纤维微塑料释放的影响,选择波轮洗衣机为研究对象,收集不同洗涤参数下纤维微塑料的释放量。记录织物在洗涤过程中水平和垂直两个方向的运动形态,提取织物运动轮廓和8个织物运动指标,研究织物运动指标与纤维微塑料释放量的关系,探讨纤维微塑料的释放机制。结果表明:随着负载量、水量、洗涤剂用量的增大和温度的升高,纤维微塑料的释放量逐步增加,为4000~7000根/m^(2),平均长度为300~400μm。纤维微塑料脱落量与织物覆盖面积、织物运动高度/宽度差均存在正相关关系,与质心-筒中心距离、质心高度/宽度差存在负相关关系,说明织物在运动中受到的各种机械力会影响纤维微塑料的释放。

海浪背景下舰船尾流感应磁场特性

基于麦克斯韦方程组以及海浪和尾流的速度场表达式得到无限深海水中海浪背景下舰船尾流感应电磁场的表达式,根据分界面处感应电磁场的连续性条件确定表达式中的待定系数。利用所得到的表达式分析无限深海水中尾流感应磁场、海浪感应磁场和海浪背景下舰船尾流感应磁场的特性。结果表明:舰船尾流感应磁场各分量的幅度在靠近海面的海水中均存在极大值点,且这些极大值点的数值和对应的海水深度均随船速的增大而增加;在海水中某一深度处舰船尾流感应磁场主要集中分布在一个“V”形平面区域内,且船速越大,“V”形区域内感应磁场周期性振荡的幅度越大,沿尾流运动方向振荡的空间间隔越大;海浪对舰船尾流感应磁场z分量的影响大于对x分量的影响。风向对尾流感应磁场的影响存在周期为π的周期性;当风速小于船速时,海浪对舰船尾流感应磁场的影响较弱,在“V”形区域内尾流感应磁场占主导作用;当风速继续增加时,海水中海浪感应磁场的强度显著增大,对尾流感应磁场的影响明显增强,在“V”形区域内尾流感应磁场逐渐被海浪感应磁场所覆盖;与风速变化所产生的影响差异比较明显相比,风向变化对尾流感应磁场影响的差别相对要小。

针对一次对流云降水反演大气垂直运动速度及雨滴谱

反演大气垂直速度和雨滴谱分布是研究云降水机制和云微物理信息的重要内容,对人工预报天气、干预天气都有重要意义。针对2021年8月29日安徽省内毫米波雷达探测到的一次对流云降水过程,处理毫米波雷达的功率谱数据并进行大气垂直速度和雨滴谱反演。在小粒子示踪法的基础上引入改进小粒子示踪法:选取有效云信号段中最小功率对应的谱点作为反演大气垂直速度的示踪物。首先,根据改进前后的小粒子示踪法分别从功率谱数据中反演大气垂直速度,并跟基数据反演大气速度的结果展开对比分析。进一步得到粒子在静止空气中的下落速度,根据现有粒子下落速度-粒子直径之间的经验公式计算反演粒子直径。研究表明:(1)采用改进后的小粒子示踪法反演大气垂直速度得到的结果比小粒子示踪法得到的结果更精确,在云层内部两者误差较大;(2)进一步得到粒子下落速度,结合探测时段的天气状况,得到的粒子速度与大气速度可很好地契合,跟对流云天气情况信息大致吻合;(3)粒子浓度是反演雨滴谱分布时需要注意的主要参数,云在快速发展过程中,内部粒子持续朝外部扩张,云内部的粒子浓度较小,云边界的粒子浓度反而较大。

南海东沙群岛以北海底沙波稳定性分析

利用在南海东沙群岛北部至西北海域为工程目的所采集的海底地形测量、底质取样、海底底流测量资料,以及以往的区域地质、地球物理资料,采用沉积学、构造学和海洋水动力学综合研究方法,对该区海底沙波形成及稳定性进行了综合分析。认为该区海底沙波是在目前水动力环境下所形成,为今生,海底表层沉积物为晚更新世地层受到冲刷改造的再沉积。沙波形成主要受潮流底流的水动力作用控制,并与构造抬升有关。沙波具有一定的活动性,主要由SE向NW方向移动,且活动性逐渐减弱。北区段海底沙波稳定,中区段海底沙波较稳定,它们对海底工程建设不会造成影响;而南区段海底沙波较为活动,当沙波发生较大规模移动时,对海底工程建设会造成一定影响。

船舶系泊动力分析数值模拟计算研究

利用动力分析方法的数学模型SHIP-MOORINGS对船舶系泊过程中的运动、波浪载荷及橡胶护舷的碰撞力进行了数值模拟计算。试验中,系泊船舶运动量、系缆力和撞击力随着波高的增大而增大,随着波浪周期的增大一般也增大,其变化关系还与船舶本身的自摇周期有关。当45°斜浪和90°横浪作用时,横移<1.0 m(PIANC,1995)的要求最容易超标,为该浪向作用下船舶作业标准的主要控制指标;当0°顺浪作用时,升沉<1.0 m的要求最容易超标,为顺浪作用下船舶作业标准的主要控制指标。在45°斜向浪作用时,沿船长方向布置的护舷所受碰撞力分布不均衡,艏、艉处的碰撞力较大,而在90°横浪和0°顺浪作用时,作业和系泊条件略好,因此控制浪向为艏来45°斜浪作用。其中,10 000DWT的船型由于吨位相对较小,风浪流作用下,运动量较大,其中横摇、横移表现最为明显。对于各泊位所选择的护舷型号,计算表明,系缆力控制工况下,护舷所受到的最大撞击力均小于其设计反力,护舷型号选择合理。