The effects of yawing motion with different frequencies on the hydrodynamic performance of floating vertical-axis tidal current turbines     

《Applied Ocean Research》2016

Under real sea conditions, the hydrodynamic performance of floating vertical-axis tidal current turbines is affected by waves and currents. The wave circular frequency is a significant factor in determining the frequencies of the wave-induced motion responses of turbines. In this study, the ANSYS-CFX software (manufacturer: ANSYS Inc., Pittsburgh, Pennsylvania, United States) is used to analyse the hydrodynamic performance of a vertical-axis turbine for different yawing frequencies and to study how the yawing frequencies affect the main hydrodynamic coefficients of the turbine, including the power coefficient, thrust coefficient, lateral force coefficient, and yawing moment coefficient. The time-varying curves obtained from the CFX software are fitted using the least-squares method; the damping and added mass coefficients are then calculated to analyse the influence of different yawing frequencies. The simulation results demonstrate that when analysing non-yawing turbines rotating under constant inflow, the main hydrodynamic coefficient time-varying curves of yawing turbines exhibit an additional fluctuation. Furthermore, the amplitude is positively correlated with the yawing frequency, and the oscillation amplitudes also increase with increasing yawing frequency; however, the average values of the hydrodynamic coefficients (except the power coefficient) are only weakly influenced by yawing motion. The power coefficient under yawing motion is lower than that under non-yawing motion, which means that yawing motion will cause the annual energy production of a turbine to decrease. The fitting results show that the damping term and the added mass term exert effects of the same level on the loads and moments of vertical-axis turbines under yawing motion. The results of this study can facilitate the study of the motion response of floating vertical-axis tidal current turbine systems in waves.  相似文献   

Axial friction response of full-scale pipes in soft clays     

《Applied Ocean Research》2016

The axial friction response of subsea pipelines in soft clays is a very important aspect for designers of subsea pipelines but the response is not well understood so far. There is a pressing need for the comprehension of the response. In this paper, model tests are performed using full-scale pipes coated with polyethylene (PE) to study the effects of the set-up period, the pipe diameter, the buried depth of the pipe, the shear strength of soft clays and the loading rate on the axial friction response of pipelines in soft clays. The variations of the axial friction coefficient are analyzed using the effective stress method based on model test results. The results show that the axial friction resistance increases with the increasing pipe diameter but the effect of the pipe diameter on the axial friction coefficient can be neglected. The ultimate axial resistance also increases with the increase of the buried depth of pipelines, the undrained shear strength of soft clays and the loading rate. The axial friction coefficient increases with the increasing loading rate. However, the axial friction coefficient decreases with the increasing buried depth. The method to determine the axial friction coefficient is developed by analyzing model test results, which considers the effects of the diameter, the buried depth, the undrained shear strength of soft clays and the loading rate. The study results not only extend the industry data base but also supply a basis to determine the axial friction coefficient of PE-coated pipes in soft clays for ocean engineering geological investigations.  相似文献   

青岛冷水团的消亡机理研究   总被引：1，自引：0，他引：1  

张启龙  刘志亮  齐继峰  杨德周  郑冬梅 《海洋学报》2016,38(5):27-33

本文基于多年月平均水温资料,分析了青岛冷水团的长消过程,并利用气候态月平均大气数据和数值模拟结果,探讨了青岛冷水团的消亡机理。结果表明,青岛冷水团3月出现,4月成型,5月最盛,6月减弱,7月消失;南黄海6-7月间偏南风的增强和温跃层以下反气旋涡的减弱是青岛冷水团消亡的动力机制,而海面净热通量的下传和水平热量的输入则是青岛冷水团消亡的热力机制。  相似文献   

Calculation method for thickness of discontinuous boundary layer of engineering pavement     

ZhongQiong Zhang  QingBai Wu  Peng Zhang  SiRu Gao 《寒旱区科学》2016,8(6):461-466

The boundary layer is a buffer layer of water and heat exchange between the atmosphere and permafrost.Based on the atmospheric boundary layer and heat transfer theory,we established a method for determining the boundary layer thickness of engineering pavement(asphalt and sand pavement)in permafrost region.The boundary layer can be divided into the Boundary Layer Above Surface(BLAS)and the Boundary Layer Below Surface(BLBS).From in-situ monitoring data,the thickness of BLAS was determined through the laminar thickness,and the thickness of BLBS was determined through ground temperature,the heat conduction function,and the mean attenuation function(α).For asphalt pavement,the BLAS thickness varied between 2.90 and 4.31 mm and that of BLBS varied between 28.00 and 45.38 cm.For sand pavement,the BLAS thickness varied between 2.55 and 3.29 mm and that of BLBS varied between 15.00 and 46.44 cm.The thickness varied with freezing and thawing processes.The boundary layer calculation method described in this paper can provide a relatively stable boundary for temperature field analysis.  相似文献   

Experimental Measurements of Solitary Wave Attenuation Over Shallow and Intermediate Submerged Canopy     

王千  郭晓宇  王本龙  房詠柳  刘桦 《海洋工程》2016,(3):375-392

Attenuations of solitary wave over a patch of submerged canopy are experimentally investigated. The submerged canopy is modeled by a group of circular cylinder array. The decay coefficients of different wave heights in two water depths along the wave flume are measured for six canopy models, including two canopy heights and three styles of arrangements. The relationships among the decay coefficient, and the dimensionless wave height, submergence ratio, relative height and arrangement of the canopy are experimentally studied. 2D PIV technique is employed to measure the representative flow field inside the canopy. A four-deck flow structure is proposed for wave flow field over shallow submerged canopy. The characteristics of shear flow inside the aligned canopy region are discussed.  相似文献   

区域地球化学评价中变异系数校正参数的意义     

刘明义  张晶  孟广路  胡立 《现代地质》2018,32(5):1074

通过对我国新疆西天山各地球化学区数据的归纳和研究,计算西天山12种常见成矿元素在各地球化学区的富集系数,提出校正系数公式,并将变异系数进行合理的校正与排序。与实际矿床和矿点结合,验证校正系数的正确性和适用性,预测元素成矿有利顺序和规律,总结出西天山富集系数与变异系数在成矿中的制约关系。该方法实现了不同成矿元素之间成矿条件的对比,拓宽了地球化学参数的适用性,提高了在勘探程度较低的地区地球化学评价方法的准确性,为地球化学评价提供科学依据。  相似文献   

基于边坡稳定性计算方法比较分析     

陈卫华  胡福洪  陈锋 《探矿工程》2018,45(9):71-74

将强度折减法应用于边坡稳定性分析中,折减土体强度,代入有限元程序进行计算,直至计算不收敛,此时的折减系数即为安全系数。结合工程实例,将强度折减法应用于边坡稳定性的分析,利用瑞典圆弧法,结合岩土工程设计类软件天汉以及有限元分析软件ABAQUS分析边坡稳定性,并对安全系数进行对比,3种计算方法得出的安全系数差别不大,安全系数精度都能满足工程要求。  相似文献   

崩塌堆积体启动坡面泥石流判别与防治 ——以北川县开坪乡平石板泥石流为例          下载免费PDF全文

佘涛  李金洋  陈欢  孙金辉  李波 《探矿工程》2018,45(8):88-92

强震区地震后大量的崩塌堆积体堆积于高陡斜坡中上部,堆积体远离居民点,一旦诱发为坡面泥石流,形成新的次生地质灾害,将严重威胁下方居民的生命财产安全。本文以北川县开坪乡平石板坡面泥石流为例,平石板沟“5.12”地震崩塌堆积体在2010、2013年强降雨作用下失稳转变为坡面泥石流淤积场镇。在平石板泥石流暴发特征介绍基础上,通过粒径不均匀系数、堆积体启动判别指标、后缘汇水面积等来分析崩塌堆积体启动条件及影响因素,并针对此类灾害发育特征,提出了通过上游稳拦固源方法进行治理的防治思路。以期为研究高陡斜坡堆积体的启动机制及防治提供一定的借鉴意义。  相似文献   

积雪升华过程对高寒湿地陆气相互作用的影响     

张海宏  苏永玲  姜海梅  晁红艳  苏文将 《冰川冻土》2018,40(6):1223-1230

利用青海玉树隆宝地区2014年12月积雪升华过程的观测资料,分析了积雪升华过程中高寒湿地陆气相互作用特征及积雪深度对陆气相互作用的影响。结果表明：在降雪和积雪升华过程中,高寒湿地浅层土壤温度在短时期内有所升高,而深层土壤温度和土壤体积含水量对降雪过程的响应不敏感。积雪升华过程中净辐射、感热通量和潜热通量的日平均值增加,向上短波辐射的日平均值减少。积雪逐渐升华导致地表吸收的能量增加,同时地表向大气传递的能量也随之增加。随着积雪的逐步升华,感热占比和潜热占比逐渐升高,而土壤热通量占比和热储存占比逐渐降低。积雪深度增加会导致地表反照率和地表比辐射率增大,感热输送系数减小。  相似文献   

逻辑回归模型在边坡稳定性分析中的应用     

王艳龙  杜立志  何赛  蔡伟嘉 《世界地质》2018,37(3):945-951

采用逻辑回归模型和确定性系数CF建立概率模型,使用收集到的22个边坡实例,将重度、内聚力、坡角、坡高、内摩擦角和孔隙压力比六个影响因子作为自变量,边坡状态作为因变量,应用SPSS取不同的滑坡概率P与不滑坡概率1-P的比值的自然对数Z进行回归分析。将获得的滑坡概率拟合模型反馈到样本参数上,对比其误差,选取Z=±10时的函数模型对另外8组边坡进行验证,证明预测模型的合理性。  相似文献