规则波作用下倾斜桩柱的受力研究

本文通过实验研究,测试了水平桩柱及倾斜桩柱在规则波作用下的波浪力。基于Morison方程和Stokes二阶波理论,分析研究了不同埋深情况下水平桩柱的受力及其水动力系数C_D、C_M随K_C数的变化规律;分析研究了不同倾角情况下,倾斜桩柱的受力及其水动力系数C_D、C_M随K_O数的变化规律,同时还探讨了在同一倾角情况下,桩柱在一端出水和全部埋于水下时,水动力系数C_D、C_M的差别。     

不同雷诺数下水平桩柱的水动力待征

本文介绍了均匀振荡流中光滑水平桩柱上水动力特征的试验研究.试验中,雷诺数Re=20000～260000(该区域为亚临界区与临界区),Kc=5～40.分析中,利用最小二乘法来确定Morison方程中的速度力系数C_(?)及惯性力系数C_M;还利用最大值法及均方根值法对合力系数C_F与升力系数C_L进行分析,所有的正向力与升力系数都作为Re及Kc数的函数给出,并且各系数相对于其平均值的均方差值也在图中示出.其主要研究成果如下:当Re≥80000时,所有的水动力系数(包括C_D、C_M,C_F与C_L),几乎与雷诺数Re无关,且各系数均随Kc数的逐渐增加而趋向于不同的常数;当Re<80000时,速度力系数C_D随Re数的增大而减小,而惯性力系数C_M随Re数的增大而增大.     

地震时海底悬跨管道动力特性试验研究

铺设在地震活跃区域的海底管道可能在地震荷载作用下发生破坏。利用水下振动台研究了海底悬跨管线在地震作用下的动力反应。试验中考虑了地震波输入方向、管道端部支撑情况、悬跨高度、悬跨长度和管内是否有水等因素。完成了这些因素组合的120组试验，得到海底悬跨管道动力响应特性。试验结果表明水中管道与陆地悬空管道的动力反应存在明显差别；悬跨长度是控制管道反应的关键，水平地震输入对管道反应起控制作用，海底悬跨管道在地震作用下的反应与受波和流作用下的反应也存在差别。     

垂直桩柱正向波流力的计算及水动力系数C_D、C_M分析方法的探讨

文中首先综述了目前常用的水动力系数C_D,C_M的分析方法,并通过大量实验结果的分析对比得出,只要按本文所定义的KC数相同,则无论是纯波场,还是波流共存场,不管是规则波情况下还是不规则波情况下,都应具有相近的C_D、C_M值。文中还通过计算值与实验结果的对比,验证了本文所述波流共存场中不规则波情况下桩柱波流力计算方法是切实可行的。     

海底悬跨管道在波流和地震联合作用时的模型试验研究

利用波浪-水流-地震联合模拟试验系统,研究了在波浪、水流和谐波地震荷载单独作用或联合作用时海底悬跨管道的动态响应特征。通过试验采集的加速度和动水压力数据分析了管道的悬跨长度、管内状态、外界荷载组合对于管道基频以及动力响应的影响规律。结果表明:随着悬跨长度的增加,管道自振频率减小且管道的动力响应显著增大;水流流速、波浪高度和周期在一定范围的增大会引起管道动力响应增大;三种荷载联合作用于管道时的动力响应大于荷载单独作用,且地震荷载起主要作用,波浪、水流荷载起次要作用。     

波流作用时海底悬跨管道水动力试验研究

利用造波机研究了波浪作用下海底悬空管道在恒定水流中的动力反应。试验中考虑了水流速度、悬空段长度、波浪高度、水深、管内是否有水等因素,得到海底悬跨管道的动力响应特性。试验结果表明:控制悬空段长度是控制海底悬跨管道动力反应的决定因素;悬跨管道上各测点的最大应变随着水深的增加而减小;管道的动力响应随着波浪高度的增大而减小;管道在管内无水时的动力反应要大于管内有水时的情况。海底悬跨管道在波流作用下的反应与受地震作用下的反应也存在差别。更多还原     

碾压混凝土坝坝前动水压力的模型试验研究

本文根据大坝整体模型的大型水下振动台试验结果以及有限元模型数值计算的结果,研究了地震作用下坝前动水压力的分布趋势及对整个坝体的影响,初步总结了地震作用下坝前动水压力的几点特性,并给出了进一步研究的建议。     

波浪条件下养殖浮球水动力系数的试验研究

该文通过试验研究获取了三种常见养殖浮球在固定状态下的水平受力,并基于改造后的Morison方程,探讨了波高参数KH、波浪周期参数KT、雷诺数Re对水动力系数DC、MC取值的影响。研究发现,波浪条件下球形结构物的受力主要是惯性力。水动力系数DC和MC基于实测历时数据,采用整体拟合法获得。研究表明,波浪参数KH、KT以及雷诺数Re对水动力系数的取值有显著影响:拖曳力系数DC与波高参数KH有较为显著的幂函数递减关系,而与波周期参数KT和雷诺数Re的关系较为离散;惯性力系数MC与波高参数KH和波周期参数KT均存在较为明显的递减规律,而随雷诺数Re的变化总体不大。最后该文给出了三种典型的养殖浮球在波浪条件下水动力系数DC和MC的经验计算公式。     

深水斜拉桥主塔模型水下振动台动力试验研究

为了探究动水压力对斜拉桥主塔地震响应的影响,探索并完善大型斜拉桥桥塔抗震分析方法 及设计理论,通过实施水下振动台模型试验,对拟设计的国内主跨最长的深水斜拉桥主塔结构在地震作 用下的动力响应进行了系统研究。通过采集并分析应变、加速度和动水压力数据,探讨了模型结构的抗 震性能和动力响应受动水压力的影响,同时验证了将动力模型试验应用于大型工程结构抗震研究的有 效性。     

大型渡槽流固动力耦合效应试验研究

以南水北调工程穿黄箱形渡槽为研究对象,采用大比尺水弹性振动渡槽模型在水平振动台上进行试验,研究了地震作用下和谐激励下水体与槽体相互作用效应和机理,并将试验结果和Housner模型计算结果进行了对比分析.结果表明流固耦合作用对渡槽结构的动力特性、振动位移和动应力响应以及槽内水体的动水压力特性有很大影响,弹性槽壁上的动水压力远大于刚性槽壁上的动水压力.试验条件下,由槽内水体晃动产生的动水压力很小.基于研究结果最后对Housner模型在抗震分析中的应用提出了修正建议.     

3-D numerical investigation of the wall-bounded concentric annulus flow around a cylindrical body with a special array of cylinders

Concentric annulus flow around a combinational cylindrical body with a special array of cylinders at five high Reynolds numbers is investigated numerically using Fluent 6.3.26 in this paper. The numerical results show a good agreement with the experimental data in regard to the axial velocity of the flow. This study focuses on the flow structure and the hydrodynamic characteristics based on the velocity distribution, the pressure distribution, streamlines and vectors under 1-D, 2-D and 3-D conditions. Meanwhile, some global parameters including the pressure coefficient, the drag coefficient and the lift coefficient are analyzed. Numerical results show that the high velocity region and the reverse wake zone with low velocity exist in some spaces due to the disturbance of the cylindrical body. Negative pressures appear in some regions. Neither a wide area vortex nor the vortex shedding appears in the wall-bounded domain. The drag along the axial direction is the main force acting on the cylindrical body in the pipe domain. The annulus flow around the cylindrical body is analyzed to reveal the hydrodynamic characteristics of the complex turbulent concentric annulus flow field due to the multi-effects in the pipeline.     

东海大桥桥梁桩柱承台水动力模型试验研究--第二部分:作用于群桩及承台上的波流力

在本系列研究第一部分单桩试验的基础上,对不规则波与均匀流共同作用于斜群桩的水动力特征进行了试验研究。由于群桩效应使得各组成桩的受力不均匀,通过试验研究,分析了群桩中各组成桩及群桩总体折减系数随KC数的变化、受水深及流速的影响。在频域内采用相关函数法进行了谱分析,得到波面谱与波力谱的相关关系。初步讨论了作用在斜群桩和承台结构上的波流力。     

波流作用下海底管道的水动力和在位稳定性研究的近代进展

近年来，随着海上油、气田的相继开发，海底管道作为输送近海油、气产品至岸上终端这样的连续结构物，其工程地位十分重要，国内外建设的数量是与日剧增。海底管道设置在恶劣的海洋环境中，将承受各类环境载荷，其中流、流引起的水动力载荷最为重要。对海底管道这样的海洋工程，保证其正常运行和结构自下而上期的安全，是直接与海底管道所受的水动力及其在位稳定性密切相关的。     

基于重叠网格技术数值模拟船舶纯摇首运动

该文采用基于非定常RANS方程的黏性数值模拟方法,对标准船模DTMB5512裸船体在平面运动机构(PMM)控制作用下的纯摇首运动进行了数值模拟。文中数值计算采用基于开源CFD工具包Open FOAM和重叠网格技术开发的多功能水动力学求解器naoe-FOAM-SJTU。根据SIMMAN2014提供的标准算例,对同一运动频率下,在Fn=0.28工况下的3种不同运动幅值的纯摇首运动进行了数值计算,得出了船舶不同工况下的阻力、侧向力和转首力矩的历时曲线。并且根据操纵性数学模型(MMG)推导出相应的水动力导数值,所有计算结果同模型试验数据吻合较好,验证了采用当前处理方法数值求解纯摇首运动的可靠性。     

微灌管道局部水头损失扩大系数的修正

根据微灌水力学原理,修正了微灌管道局部水头损失扩大系数,并对影响局部水头损失扩大系数的因素进行了敏感性分析。结果表明:当微灌管道出水口较少及进口端长度不等于出水口间距时,采用修正后的微灌管道局部水头损失扩大系数可以提高管道总水头损失的计算精度。     

FLOW AND HEAT TRANSFER OF OLDROYD-B FLUIDS IN A ROTATING CURVED PIPE

The flow and convected heat transfer of the Oldroyd-B fluids in a rotating curved pipe with circular cross-section were investigated by employing a perturbation method. A perturbation solution up to the second order was obtained for a small curvature ratio, κ. The variations of axial velocity distribution and secondary flow structure with F, Re and We were discussed in detail in order to investigate the combined effects of the three parameters on flow structure. The combined effects of the Coriolis force, inertia force and elastic force on the temperature distribution were also analyzed, which are greater than the adding independent effects of the three forces. The variations of the flow rate and Nusselt number with the rotation, inertia and elasticity were examined as well. The results show the characteristics of the heat and mass transfer of the Oldroyd-B fluids in a rotating curved pipe.     

Hydrodynamic behaviour of European black poplar (Populus nigra L.) under coppice management along Mediterranean river ecosystems

This study examined the hydrodynamic behaviour of European black poplar (Populus nigra L.) under coppice management in riparian areas with a multidisciplinary approach. An innovative procedure on the basis of the combination of plant allometric relations and hydrodynamic models was applied to assess drag forces and plant hydrodynamic bending as function of the basal diameter and module of elasticity, with a probabilistic approach. Cuttings of European black poplar from 2 close riverine environments of Southern Italy have been planted and subjected to the same coppice management strategy. The 2 different 3‐year‐old shoot poplar ensembles exhibited statistically similar morphological traits but stems with different module of elasticity. Drag forces were simulated with a model on the basis of the vegetative Cauchy number. Plant deformation under the hydrodynamic load was modelled as a base‐mounted cantilever beam. The differences in the observed elasticity were verified to be also significant from a hydrodynamic perspective. Diagrams were drawn to describe plant bending, drag forces, and basal momentum as function of basal diameter, accounting for the uncertainty in the module of elasticity. These results can be exploited for identifying objective hydrodynamic criteria to be adopted for coppice management of riparian woody vegetation in human controlled river ecosystems.     

Theoretical and numerical study of hydraulic characteristics of orifice energy dissipator

Different factors affecting the efficiency of the orifice energy dissipator were investigated based on a series of theoretical analyses and numerical simulations.The main factors investigated by dimension analysis were identified,including the Reynolds number(Re),the ratio of the orifice diameter to the inner diameter of the pipe(d/D),and the ratio of distances between orifices to the inner diameter of the pipe(L/D).Then,numerical simulations were conducted with a k-ε two-equation turbulence model.The calculation results show the following:Hydraulic characteristics change dramatically as flow passes through the orifice,with abruptly increasing velocity and turbulent energy,and decreasing pressure.The turbulent energy appears to be low in the middle and high near the pipe wall.For the energy dissipation setup with only one orifice,when Re is smaller than 105,the orifice energy dissipation coefficient K increases rapidly with the increase of Re.When Re is larger than 105,K gradually stabilizes.As d/D increases,K and the length of the recirculation region L1 show similar variation patterns,which inversely vary with d/D.The function curves can be approximated as straight lines.For the energy dissipation model with two orifices,because of different incoming flows at different orifices,the energy dissipation coefficient of the second orifice(K2)is smaller than that of the first.If L/D is less than 5,the K value of the L/D model,depending on the variation of K2,increases with the spacing between two orifices L,and an orifice cannot fulfill its energy dissipation function.If L/D is greater than 5,K2 tends to be steady; thus,the K value of the L/D model gradually stabilizes.Then,the flow fully develops,and L has almost no impact on the value of K.     

斜向波浪作用下海底管线周围水动力特性数值研究

管线周围的水动力因素是管线冲刷的主要原因之一。基于OpenFOAM开源程序,结合改进后的速度入口造波法,建立三维波浪数值水槽,耦合分离涡紊流模拟方法,对管线周围水动力特性进行研究。分析了波浪入射角为30°、45°、60°和90°和KC数为5、8和11的波浪作用下,管线周围的流场结构进行分析,探讨入射角和KC数对管线周围水流结构的影响规律。结果表明:波浪作用下,入射角和KC数对管线周围水流结构具有较明显的影响。且随入射角增大,管上表面水流分离现象明显,管后正负涡量相邻分布的特征减弱;随KC数增大,管线附近涡量分布范围增大,正负涡量逐渐分离。