Estimation of eddy viscosity on the South China Sea shelf with adjoint assimilation method   总被引：2，自引：0，他引：2  

ZHANGYanwei  TIANJiwei  XIELingling 《海洋学报(英文版)》2009,28(5):9-16

The eddy viscosity of the ocean is an important parameter indicating the small-scale mixing process in the oceanic interior water column.Ekman wind-driven current model and adjoint assimilation technique are used to calculate the vertical profiles of eddy viscosity by fitting model results to the observation data.The data used in the paper include observed wind data and ADCP data obtained at Wenchang Oil Rig on the SCS (the South China Sea) shelf in August 2002.Different simulations under different wind conditions are analyzed to explore how the eddy viscosity develops with varying wind field.The results show that the eddy viscosity endured gradual variations in the range of 10^-3-10^-2 m²/s during the periods of wind changes.The mean eddy viscosity undergoing strong wind could rise by about 25% as compared to the value under weak wind.  相似文献   

Suppression of Flow Separation Around A Circular Cylinder by Utilizing Lorentz Force   总被引：2，自引：0，他引：2  

张辉  范宝春  陈志华  周本谋 《中国海洋工程》2008,22(1):87-95

Both experimental and numerical investigations on the flow past a cylinder under the influence of Lorentz force （electromagnetic force） were conducted in an electrically low-conducting fluid. The Lorentz force is applied beth locally, wholly and periodically on the surface of the cylinder, and their control effects for flow ,separation were investigated Both experimental and numerical results show that Lorentz force can suppress the flow separation with Lorentz force applied on beth local and whole surface of the cylinder. However, when the periodic and opposite Lorentz force adopted, the cylinder wake cannot be stabilized.  相似文献   

大亚湾海水污染扩散试验及涡动扩散系数的估计     

张观希  黄小平  杜完成  郑庆华  何清溪 《热带海洋学报》1997,(1)

水质数学模拟扩散系数大亚湾现场求取实验，采用示踪剂扩散实验法。示踪剂扩散实验的目的，在于了解水流运动的稀释扩散能力，根据示踪剂运动轨迹和浓度分布，求出水平纵向扩散系数和横向扩散系数，供水质数学模拟应用。  相似文献   

碳化作用对水泥固化/稳定化铅污染土溶出特性影响   总被引：1，自引：0，他引：1  

《岩土力学》2016,(1)

采用室内加速碳化试验方法,分析了碳化作用对水泥固化/稳定化重金属污染土淋滤特性的影响规律。对人工配制的不同浓度铅污染土进行水泥固化/稳定化处理,标准养护28 d后对部分土样进行加速碳化试验,剩余试样继续标准养护。通过半动态淋滤试验方法测试了碳化后试样和标准养护试样的铅溶出量,并计算铅扩散系数、固化/稳定化土淋滤指数,分析碳化作用对水泥固化/稳定化铅污染土环境安全性以及铅溶出机制的影响。结果表明,单位面积上铅的溶出速率随淋滤时间的增加而降低;浸出液中铅累计溶出量与淋滤时间的平方根呈近似线性关系;碳化养护试样的铅累计溶出量是标准养护试样的0.68~0.91倍,碳化有利于铅的固化/稳定化。固化稳定化处理后铅的扩散系数在2.12×10-12~1.39×10-9 cm~2/s之间,淋滤指标在8.86~11.7之间,且碳化作用下铅的扩散系数进一步降低,淋滤指标略有升高。低铅含量土样中铅溶出机制为表面侵蚀,而高铅含量试样中铅溶出机制为表面侵蚀和扩散共同作用,并以扩散为主。  相似文献   

一种井中瞬变电磁异常反演方法   总被引：2，自引：0，他引：2  

杨毅  邓晓红  张杰  武军杰  王兴春 《物探与化探》2014,(4)

井中瞬变电磁法在深部找矿中得到广泛应用并取得丰硕成果,然而解释技术目前仍以定性和半定量为主,这在很大程度上制约了该方法的运用和推广。鉴于此,笔者采用遗传算法开展了基于等效涡流的井中瞬变电磁纯异常反演研究,反演以导体内感应电流环为对象,能够准确地确定井中或井旁异常体的尺度、倾角、中心坐标等参数。对Maxwell软件薄板模型的正演数据和实测数据的反演结果进一步验证了算法的正确性和适用性。  相似文献   

Estimation of eddy heat transport in the global ocean from Argo data   总被引：6，自引：2，他引：4  

ZHANG Zhiwei  ZHONG Yisen  TIAN Jiwei  YANG Qingxuan  ZHAO Wei 《海洋学报(英文版)》2014,33(1):42-47

The Argo data are used to calculate eddy(turbulence)heat transport(EHT)in the global ocean and analyze its horizontal distribution and vertical structure.We calculate the EHT by averaging all the v′,T′profiles within each 2×2 bin.The velocity and temperature anomalies are obtained by removing their climatological values from the Argo"instantaneous"values respectively.Through the Student’s t-test and an error evaluation,we obtained a total of 87%Argo bins with significant depth-integrated EHTs(D-EHTs).The results reveal a positive-and-negative alternating D-EHT pattern along the western boundary currents(WBC)and Antarctic Circumpolar Current(ACC).The zonally-integrated D-EHT(ZI-EHT)of the global ocean reaches 0.12 PW in the northern WBC band and–0.38 PW in the ACC band respectively.The strong ZI-EHT across the ACC in the global ocean is mainly caused by the southern Indian Ocean.The ZI-EHT in the above two bands accounts for a large portion of the total oceanic heat transport,which may play an important role in regulating the climate.The analysis of vertical structures of the EHT along the 35 N and45 S section reveals that the oscillating EHT pattern can reach deep in the northern WBC regions and the Agulhas Return Current(ARC)region.It also shows that the strong EHT could reach 600 m in the WBC regions and 1 000 m in the ARC region,with the maximum mainly located between 100 and 400 m depth.The results would provide useful information for improving the parameterization scheme in models.  相似文献   

Energetics of lateral eddy diffusion/advection：Part Ⅰ. Thermodynamics and energetics of vertical eddy diffusion   总被引：2，自引：2，他引：0  

HUANG Rui Xin 《海洋学报(英文版)》2014,33(3):1-18

Two important nonlinear properties of seawater thermodynamics linked to changes of water density, cabbeling and elasticity(compressibility), are discussed. Eddy diffusion and advection lead to changes in density; as a result, gravitational potential energy of the system is changed. Therefore, cabbeling and elasticity play key roles in the energetics of lateral eddy diffusion and advection. Vertical eddy diffusion is one of the key elements in the mechanical energy balance of the global oceans. Vertical eddy diffusion can be conceptually separated into two steps: stirring and subscale diffusion. Vertical eddy stirring pushes cold/dense water upward and warm/light water downward; thus, gravitational potential energy is increased. During the second steps, water masses from different places mix through subscale diffusion, and water density is increased due to cabbeling. Using WOA01 climatology and assuming the vertical eddy diffusivity is equal to a constant value of 2×103 Pa2/s, the total amount of gravitational potential energy increase due to vertical stirring in the world oceans is estimated at 263 GW. Cabbeling associated with vertical subscale diffusion is a sink of gravitational potential energy, and the total value of energy lost is estimated at 73 GW. Therefore, the net source of gravitational potential energy due to vertical eddy diffusion for the world oceans is estimated at 189 GW.  相似文献   

Effect of tropical cyclone intensity and instability on the evolution of spiral bands     

Hong Huang  Yongqiang Jiang  Zhongyi Chen  Jian Luo  Xuezhong Wang 《大气科学进展》2014,31(5):1090-1100

The evolution of spiral-band-like structures triggered by asymmetric heating in three tropical-cyclone-like vortices of different intensities is examined using the Three-Dimensional Vortex Perturbation Analyzer and Simulator （3DVPAS） model. To simulate the spiral bands, asymmetric thermal perturbations are imposed on the radius of maximum wind （RMW） of vortices, which can be considered as the location near the eyewall of real tropical cyclones （TCs）. All the three vortices experience a hydrostatic adjustment after the introduction of thermal asymmetries. It takes more time for weaker and stable vortices to finish such a process. The spiral-band-like structures, especially those distant from the vortex centers, form and evolve accompanying this process. In the quasi-balance state, the spiral bands are gradually concentrated to the inner core, the wave behavior of which resembles the features of classic vortex Rossby （VR） waves. The unstable vortices regain nonhydrostatic features after the quasi-balance stage. The spiral bands further from the vortex center, similar to distant spiral bands in real TCs, form and maintain more easily in the moderate basic-state vortex, satisfying the conditions of barotropic instability. The widest radial extent and longest-lived distant bands always exist in weak and stable vortices. This study represents an attempt to determine the role of TC intensity and stability in the formation and evolution of spiral bands via hydrostatic balance adjustment, and provides some valuable insights into the formation of distant spiral rainbands.  相似文献   

Effect of Baroclinicity on Vortex Axisymmetrization.Part Ⅰ：Barotropic Basic Vortex     

Melinda S.PENG  ;Jiayi PENG  ;Tim LI  ;Eric HENDRICKS 《大气科学进展》2014,31(6):1256-1266

The barotropic and baroclinic disturbances axisymmetrized by the barotropic basic vortex are examined in an idealized modeling framework consisting of two layers.Using a Wentzel-Kramers-Brillouin approach,the radial propagation of a baroclinic disturbance is shown to be slower than a barotropic disturbance,resulting in a slower linear axisymmetrization for baroclinic disturbances.The slower-propagating baroclinic waves also cause more baroclinic asymmetric kinetic energy to be transferred directly to the barotropic symmetric vortex than from barotropic disturbances,resulting in a faster axisymmetrization process in the nonlinear baroclinic wave case than in the nonlinear barotropic wave case.  相似文献   

海域湍流扩散系数的确定     

王发君 《海洋通报》1992,11(2):9-12

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