顺逆铣加工刷柄曲面的若干特性分析     

李巨光  王继尚 《中国海洋大学学报(自然科学版)》1995,(Z1)

刷柄侧曲面是典型的曲线形外型表面，其加工方式有顺铣和逆铣两种方法．本文分析了两种铣削方法分别对铣削过程中的切削力，工件表面不平度等几个重要参数的影响，提出了木制品曲面加工中顺铣较逆铣具有消耗动力小，刀具耐用度高，工件不易破裂，加工表面平整等几个突出优点．  相似文献   

Sloshing in a three-dimensional rectangular tank: Numerical simulation and experimental validation   总被引：1，自引：0，他引：1  

Hakan Akyild&#x;z  N. Erdem Ünal 《Ocean Engineering》2006,33(16):2135-2149

Pressure variations and three-dimensional effects on liquid sloshing loads in a moving partially filled rectangular tank have been carried out numerically and experimentally. A numerical algorithm based on the volume of fluid (VOF) technique is used to study the non-linear behavior and damping characteristics of liquid sloshing. A moving coordinate system is used to include the non-linearity and avoid the complex boundary conditions of moving walls. The numerical model solves the complete Navier–Stokes equations in primitive variables by using of the finite difference approximations. In order to mitigate a series of discrete impacts, the signal computed is averaged over several time steps. In order to assess the accuracy of the method used, computations are compared with the experimental results. Several configurations of both baffled and unbaffled tanks are studied. Comparisons show good agreement for both impact and non- impact type slosh loads in the cases investigated.  相似文献   

Validation of a regional Indonesian Seas model based on a comparison between model and INSTANT transports     

D. Rosenfield  V. Kamenkovich  K. O’Driscoll  J. Sprintall 《Dynamics of Atmospheres and Oceans》2010

The International Nusantara Stratification and Transport (INSTANT) program measured currents through multiple Indonesian Seas passages simultaneously over a three-year period (from January 2004 to December 2006). The Indonesian Seas region has presented numerous challenges for numerical modelers — the Indonesian Throughflow (ITF) must pass over shallow sills, into deep basins, and through narrow constrictions on its way from the Pacific to the Indian Ocean. As an important region in the global climate puzzle, a number of models have been used to try and best simulate this throughflow. In an attempt to validate our model, we present a comparison between the transports calculated from our model and those calculated from the INSTANT in situ measurements at five passages within the Indonesian Seas (Labani Channel, Lifamatola Passage, Lombok Strait, Ombai Strait, and Timor Passage). Our Princeton Ocean Model (POM) based regional Indonesian Seas model was originally developed to analyze the influence of bottom topography on the temperature and salinity distributions in the Indonesian seas region, to disclose the path of the South Pacific Water from the continuation of the New Guinea Coastal Current entering the region of interest up to the Lifamatola Passage, and to assess the role of the pressure head in driving the ITF and in determining its total transport. Previous studies found that this model reasonably represents the general long-term flow (seasons) through this region. The INSTANT transports were compared to the results of this regional model over multiple timescales. Overall trends are somewhat represented but changes on timescales shorter than seasonal (three months) and longer than annual were not considered in our model. Normal velocities through each passage during every season are plotted. Daily volume transports and transport-weighted temperature and salinity are plotted and seasonal averages are tabulated.  相似文献   

Derivation and application of new equations for radiation stress and volume flux     

Baoxing Wang  Andrew J. Chadwick  Ashwini K. Otta 《Coastal Engineering》2008

In this paper, new expressions of radiation stress and volume flux for long waves have been analytically derived by inclusion of higher-order surface elevations up to the sixth-order. To quantify these expressions, surface elevations along a beach are first simulated using the fully nonlinear Boussinesq-type model COULWAVE. Then, based on the large amount of numerical data, new equations for radiation stress and volume flux are statistically formulated. The research unveils the essential roles of the Ursell parameter, Irribarren number and wave steepness described by the local wave height, wave length and bottom slope. The study shows the importance of nonlinear wave properties in wave-induced currents and mean water levels (set-up/down). The higher-order formulations produce lower values for radiation stress and volume flux than calculated from the lower-order and linear waves. Case studies suggest that the new formulations produce an accurate estimation for mean water level. However, improvement on the computed current profiles is marginal for some cases. This implies that the accurate prediction of the current profile would require more than just the proposed improvement of the radiation stress and volume flux.  相似文献   

Conditions for instabilities in collapsible solids including volume implosion and compaction banding     

Ronaldo I. Borja 《Acta Geotechnica》2006,1(2):107-122

We review conditions for material instabilities in porous solids induced by a bifurcation of solution into non-unique strain rate fields. Bifurcation modes considered include jumps in the strain rate tensor of ranks one and higher representing deformation band and diffuse instability modes, respectively. Eigenmodes (e-modes) are extracted for each type of instability to fully characterize various frameworks of deformation in collapsible solids. For diffuse instability these e-modes are determined from a homogeneous system of linear equations emanating from the condition of zero jump in the stress rate tensor, which in turn demands that the tangent constitutive tensor be singular for the existence of nontrivial solutions. For isotropic materials we describe two types of singularity of the constitutive tensor: (a) singularity of the constitutive matrix in principal axes, and (b) singularity of spin. Accordingly, we derive the e-modes for each type of singularity. We utilize the singularity of the constitutive matrix in principal axes as a precursor to volume implosion in collapsible solids such as loose sands undergoing liquefaction instability and high-porosity rocks undergoing cataclastic flow. Finally, we compare conditions and e-modes for volume implosion and compaction banding, two similar failure modes ubiquitous in granular soils and rocks.Supported by U.S. Department of Energy, Grant DE-FG02-03ER15454, and U.S. National Science Foundation, Grants CMS-0201317 and CMS-0324674.  相似文献   

体元结构模型在三维地震模型正演模拟研究中的应用   总被引：7，自引：0，他引：7       下载免费PDF全文

毛小平  黄延祜 《地球物理学报》1998,41(6):833-840

本文采用双三次康氏（Coons）曲面模拟地震界面,提出了用体元结构来表示复杂构造地区的三维地震模型,同时以此为基础建立了灵活的动态射线追踪过程,实现了快速的、更具实用性的三维地震模型的正演模拟．  相似文献   

频域激发极化法中体极化与面极化内在联系的探讨   总被引：2，自引：0，他引：2  

王继伦 《地球物理学报》1989,32(5):593-599

矿化的体极化介质,其激发极化效应来自其中所含电子导电矿物颗粒的表面极化效应。基于上述认识,本文从理论上推导出含球状电子导体的体极化介质复电阻率的“微观”数学表达式。将它与体极化介质复电阻率的“宏观”表达式--Cole-Cole模型相比较,得出了:1.Cole-Cole模型中的特征参量与球状电子导体的表面极化系数、含量以及导体半径等的综合关系式;2.电子导体表面极化系数在频域中的一般表达式。这表达式同目前在实验室中观测到的结果是一致的。  相似文献   

地热资源评价的蒙特卡罗法   总被引：2，自引：0，他引：2  

王心义  廖资生  韩星霞  王金生 《水文地质工程地质》2002,29(4):10-13

目前国内外评价地热资源的方法 ,均将热储参数作为定值而未考虑其随机特性。蒙特卡罗法是以热储参数的随机特征为基础建立的 ,并且通过计算可以给出结果的可信度。本文在论述蒙特卡罗法基本原理的基础上 ,结合开封市地热系统 ,分别利用蒙特卡罗法和单元热储体积法对地热资源进行了计算 ,经对比分析得出的地热资源量为 133 0 95 5×10 1 3 Kcal,相当于 1 5 476× 10 1 2 度电或 7 7381× 10 8t煤所产生的热量 ,为开封市地热资源的合理开发提供了科学依据。  相似文献   

Numerical simulation of fluid–structure interaction using a combined volume of fluid and immersed boundary method     

Linwei Shen  Eng-Soon Chan 《Ocean Engineering》2008,35(8-9):939-952

In this work, a combined immersed boundary (IB) and volume of fluid (VOF) methodology is developed to simulate the interactions of free-surface waves and submerged solid bodies. The IB method is used to account for the no-slip boundary condition at solid interfaces and the VOF method, utilizing a piecewise linear interface calculation, is employed to track free surfaces. The combined model is applied in several case studies, including the propagation of small-amplitude progressive waves over a submerged trapezoidal dike, a solitary wave traveling over a submerged rectangular object, and wave generation induced by a moving bed. Numerical results depicting the free-surface evolutions and velocity fields are in good agreement with either experimental data or numerical results obtained by other researchers. In addition, the simplification of the initial free-surface deformation used in most tsunami earthquake source study is justified by the present model application. The methodology presented in the paper serves as a good tool for solving many practical problems involving free surfaces and complex boundaries.  相似文献   

Water masses and currents of deep circulation southwest of the Shatsky Rise in the western North Pacific     

Masaki Kawabe  Shinzou Fujio  Daigo Yanagimoto  Kiyoshi Tanaka   《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1675-1687

We conducted full-depth hydrographic observations in the southwestern region of the Northwest Pacific Basin in September 2004 and November 2005. Deep-circulation currents crossed the observation line between the East Mariana Ridge and the Shatsky Rise, carrying Lower Circumpolar Deep Water westward in the lower deep layer (θ<1.2 °C) and Upper Circumpolar Deep Water (UCDW) and North Pacific Deep Water (NPDW) eastward in the upper deep layer (1.3–2.2 °C). In the lower deep layer at depths greater than approximately 3500 m, the eastern branch current of the deep circulation was located south of the Shatsky Rise at 30°24′–30°59′N with volume transport of 3.9 Sv (1 Sv=10⁶ m³ s⁻¹) in 2004 and at 30°06′–31°15′N with 1.6 Sv in 2005. The western branch current of the deep circulation was located north of the Ogasawara Plateau at 26°27′–27°03′N with almost 2.1 Sv in 2004 and at 26°27′–26°45′N with 2.7 Sv in 2005. Integrating past and present results, volume transport southwest of the Shatsky Rise is concluded to be a little less than 4 Sv for the eastern branch current and a little more than 2 Sv for the western branch current. In the upper deep layer at depths of approximately 2000–3500 m, UCDW and NPDW, characterized by high and low dissolved oxygen, respectively, were carried eastward at the observation line by the return flow of the deep circulation composing meridional overturning circulation. UCDW was confined between the East Mariana Ridge and the Ogasawara Plateau (22°03′–25°33′N) in 2004, whereas it extended to 26°45′N north of the Ogasawara Plateau in 2005. NPDW existed over the foot and slope of the Shatsky Rise from 29°48′N in 2004 and 30°06′N in 2005 to at least 32°30′N at the top of the Shatsky Rise. Volume transport of UCDW was estimated to be 4.6 Sv in 2004, whereas that of NPDW was 1.4 Sv in 2004 and 2.6 Sv in 2005, although the values for NPDW may be slightly underestimated, because they do not include the component north of the top of the Shatsky Rise. Volume transport of UCDW and NPDW southwest of the Shatsky Rise is concluded to be approximately 5 and 3 Sv, respectively. The pathways of UCDW and NPDW are new findings and suggest a correction for the past view of the deep circulation in the Pacific Ocean.  相似文献