三翼钻头的结构改进及其在硬粘土地层中的应用     

李邵军  梁群 《地质与勘探》2000,36(2):43-44,62

针对三翼钻头在硬粘土地层的钻进所遇到的问题提出了改进措施 ,对去掉护圈、改变副吸渣口形状 ,调整前角角度、切削齿的排列等问题进行了探讨 ,基本解决了三翼钻头易糊钻、钻速缓慢的两大难题。  相似文献   

南沙群岛海域近海面粗糙度、中性曳力系数及总体交换系数研究     

高志球  马耀明  王介民  张庆荣 《热带海洋学报》2000,19(1)

根据 1 994年 9月 1 8— 30日南沙群岛海域渚碧礁的近海面大气湍流观测实验资料 ,分别计算了该海域光滑海面和粗糙海面上的空气动力粗糙度 (z0 )、中性曳力系数 (CDN)。利用Brutsaert的假定 ,推导了一组求取标量粗糙度 (zT,zQ)、整体输送系数 (感热交换系数CHN、水汽交换系数CEN)的公式。在此基础上分别计算和分析了该海域近海面光滑海面和粗糙海面上z0 ,zT,zQ,CDN,CHN,CEN 及它们关于水平风速u分量的分布 ,并得到了一些有意义的结论。  相似文献   

Hybrid Analysis Approach for Stochastic Response of Offshore Jacket Platforms   总被引：2，自引：0，他引：2  

金伟良  郑忠双  李海波  张立 《中国海洋工程》2000,14(2):143-152

The dynamic response of offshore platforms is more serious in hostile sea environment than inshallow sea.In this paper,a hybrid solution combined with analytical and numerical method is proposedto compute the stochastic response of fixed offshore platforms to random waves,considering wave-struc-ture interaction and non-linear drag force.The simulation program includes two steps:the first step is theeigenanalysis aspects associated the structure and the second step is response estimation based on spectralequations.The eigenanalysis could be done through conventional finite element method conveniently andits natural frequency and mode shapes obtained.In the second part of the process,the solution of theoffshore structural response is obtained by iteration of a series of coupled spectral equations.Consideringthe third-order term in the drag force,the evaluation of the three-fold convolution should be demanded fornonlinear stochastic response analysis.To demonstrate this method,a numerical analysis is carrie  相似文献   

海洋边界层内风、浪相互作用研究进展   总被引：1，自引：1，他引：0  

李建东  陈希  蒋国荣  刘庭杰 《海洋预报》2005,22(1):58-66

鉴于海洋边界层内风、浪相互作用在海洋、大气研究中的重要意义,本文较详细地回顾、总结了国内外有关海洋边界层风、浪相互作用的研究进展：由最初的关于风应力和空气动力粗糙长度的统计研究发展到后来的利用模式探讨海洋边界层的结构和风、浪耦合机制。最后简单讨论了风、浪耦合研究中存在亟待解决的问题以及未来的研究前景。  相似文献   

Hydrodynamic performance improvement on small horizontal axis current turbine blade using different tube slots configurations     

《Applied Ocean Research》2019

Vortex generators are used extensively as a passive flow control devices to delay or remove the boundary layer separation, which affects the hydrodynamic performance of the hydrofoil. In this paper, a new approach is introduced to overcome the boundary layer separation on the NACA S1210 hydrofoil. The outcome of tube slots combination in the S1210 hydrofoil on the boundary layer separation are numerically investigated. The performance is compared with respect to the force coefficients and glide ratio. The effects of tube slot inlet positions with different diameters on S1210 hydrofoil are presented here. The results show that the smaller diameter tube slots starting near the leading edge improves the hydrodynamics performance of the hydrofoil.  相似文献   

北冰洋浮冰站近地层参数的观测估算   总被引：1，自引：1，他引：0       下载免费PDF全文

王先桥  杨清华  李诗民  周明煜  乔然  吕洪刚 《海洋学报》2011,33(2):36-41

利用2008年8月20～27日我国第3次北极考察队在85°N附近设立的冰站上进行的湍流通量、辐射观测所获取的相关资料,采用涡动相关法对夏季北冰洋浮冰下垫面的近地层参数进行了估算.结果显示,观测期间浮冰区冰雪面的平均感热、潜热和净辐射通量分别是0.2 W/m2,1.2 W/m2和9.9 W/m2,表明下垫面获得的大部分热...  相似文献   

The Influence of Advection Schemes and Turbulence Closure Models on Drag Coefficient Calculation Around a Circular Cylinder at High Reynolds Number     

LIN Zhenhua  ZHAO Dongliang  SONG Jinbao 《青岛海洋大学学报(英文版)》2011,(3):229-233

  相似文献   

Characteristics of Drag Coefficient in Different Coastal Regions of the South China Sea Under Tropical Cyclones–An Observational Study     

袁金南  宋丽莉  陈雯超  植石群  毕雪岩  刘春霞  黄辉军 《热带气象学报(英文版)》2020,26(4):417-427

To investigate the values of 10-m drag coefficient (CD) in different coastal areas under the influence of tropical cyclones, the present study used the observational data from four towers in different coastal areas of the South China Sea (SCS) during six tropical cyclone (TC) passages, and employed the eddy covariance method and the flux profile method. The analysis of footprint showed that the fluxes at Zhizai Island (ZZI), Sanjiao Island (SJI) and Donghai Island (DHI) were influenced basically by the ocean, and the flux at Shangyang Town (SYT) was influenced mainly by the land. The results showed that the dependence relationships of CD on 10-m wind speed (U10) in four different coastal areas under the influence of TCs were different. CD at ZZI and SJI initially increased and then decreased as U10 increased, similar to the pattern over the ocean. CD at ZZI and SJI represented the values over shallow water with seawater depths of ~7 m and ~2 m, respectively. Moreover, the critical wind speed at which CD peaked gradually decreased as the seawater depth became shallower in the coastal areas. CD at DHI and SYT decreased monotonously as U10 increased, similar to the pattern over the land. CD at DHI represented the value over the transition zone from shallow water to coastal land, and CD at SYT represented the value over the coastal land. Meanwhile, the eddy covariance method and the flux profile method were compared at ZZI and SYT during TC passages. It was found that their CD values obtained by the two methods were close. Finally, the parameterizations of observed u* and CD as a function of U10 over four different coastal areas were given under the influence of high winds. These parameterizations of observed C may be used in high-resolution numerical models for landfalling TC forecast.  相似文献   

STUDY ON FLUXES OF MOMENTUM AND SENSIBLE HEAT,THE DRAG COEFFICIENT C_D AND ROUGHNESS Z_O     

宋西龙  胡敦欣 《中国海洋湖沼学报》1994,(3)

In this paper,fluxes of momentum and sensible heat are discussed with the data callected by tetheredballoon sounding system over the Philippine Sea during the cruise of the R/V SCIENCE 1 from Septem-ber through October in 1987.These fluxes were calculated using the semiempirical flux-profile relationshipsof Monin-Obkhov similarity theory with observed data.The friction velocity U.was determined by theobserved data's least-square fit with the similarity formulae under stable,neutral and unstable conditions.The roughness Z_0 was determined by Z_0=a_1(U./g),then substituted into the similarity formulae to com-pute U.again.The final values of U.and Z_0 could be determined through this iteration.The fluxtemperature θ.was calculated from the temperature profile with Z_0 determined above.Finally the fluxes'of momentum and sensible heat,and the drag coefficient C_D were obtained by computation with U.,θ.and the wind speed(U_(10))at 10 meters above the sea surface.  相似文献   

磁感应阻力对导体卫星在圆形轨道上的摄动影响     

李林森 《天文研究与技术》2004,1(4):274-281

用功能转换原理和摄动理论的两种方法重点研究了导体卫星在地球磁场和有电导率介质空间飞行时磁感应阻力对圆形轨道半径的摄动影响。理论研究表明：导体卫星在圆形轨道上受磁感应阻力后轨道半径有随时间变化的长期摄动效应外还有周期性变化。此外，文中还讨论了磁感应阻力对圆形轨道的其它要素的摄动影响概况。  相似文献