探针杆挠曲对水流场测量的影响研究

绕流阻力引起探针杆弹性挠曲，针头挠度和转角造成测点位置误差和流速方向或分量测量误差。本文提出根据探针测定的原始速度分布求解针头在各测点处的转角，进而确定实际流速方向、流速分量和测点位置误差。方法成功地用于探针测定的三维流场的误差计算和修正。结果表明，沿杆长方向的流速误差最大，不能忽视。最后，给出误差修正计算实用近似方法。     

螺旋桨尾流场的数值计算方法

通过解析公式计算得到面源和面偶的诱导速度,在面偶附近区域,用涡环代替面偶,计算得到螺旋桨的速度场,根据尾涡面必须和当地流体流速相切的原则,修正原来尾涡面的形状,逐步迭代直至螺旋桨的尾涡形状收敛。将这种方法计算得到的螺旋桨水动力性能和试验结果进行了比较分析,证明该方法可以提高螺旋桨水动力性能在非设计工况下的预报精度。     

基于负荷裕度最大化的发电出力优化（二）模型求解

在修正方向已知的条件下,首先建立了修正步长的优化模型,并通过对前后2次出力方式修正角度的限制,使模型只需进行一次迭代即可确定较优的修正步长,在保证收敛精度的同时大大减小了计算量;然后通过已知的修正方向和步长更新发电机出力方式,并在新的发电机出力方式下重新计算崩溃点,通过交替迭代使负荷裕度和发电机出力方式逐步收敛于最优值。在多个IEEE标准算例上验证了所提出方法的快速、有效性,并根据仿真结果对有功出力优化在提升系统负荷裕度方面的作用进行了总结。     

河流可视化模型研究与开发

应用VB6.0集成平台,对河道水流一维、二维数学模型进行可视化开发。系统主要的关键技术有河网断面图、二维矢量场、二维标量场、流速、流向验证等的显示。应用该系统,模拟了西江河网各断面的水力要素(水位和流量)、长江昌门溪—大埠街河段的流场和水位场,计算条件的输入、计算结果的显示,都可通过界面输入和菜单操作,实现了河流数值模拟的可视化。该系统人机交互方便、集成度高、模拟精度较高。     

测深杆固定流速仪在河道测流中的应用

本文探讨使用测深杆固定流速仪测流,对测深杆的抗剪、抗弯性能进行计算分析,说明测深杆固定流速仪测流是可行的。     

一种简便的非交错曲线网格三维水流数值模型

在平面非正交曲线，垂向采用σ-坐标系统条件下，建立非交错网格变量布置的水深-流速迭代计算模式。由水深校正法求解水体自由表面和流速场耦合问题，为避免压力场波动，采用动量插值方法计算交界面处流速插值。运用该模式模拟了南京河段天然“S”型弯道三维水流流动。     

大型卧式液压油缸挠度与稳定性计算

 大型卧式液压油缸挠度与稳定性计算是实际工程需要解决的问题。以油缸的阶梯形压弯杆模型为基础，通过建立和求解挠曲方程， 获得了其挠度及临界压力的解析计算方法。经计算与试验实例验证表明，该算法具有较高的计算精度。还分析了油缸挠度对稳定性的不利影响，提出对于具有较大初始挠度的油缸，除关心其临界压力外，还应以极限压力作为其次稳定性设计的控制因素。     

水深测量误差对流量资料整编精度的影响分析

为了研究在测深杆悬挂流速仪法实测流量时,水深观读误差对流量成果精度的影响,作者采用实例数据进行了对比分析。结果表明,在测深杆迎水面和背水面观读水深时所产生的误差都会给流量测验精度带来较大影响,而且会引起水位～流量关系曲线的明显偏离,给流量资料整编成果带来较大误差,在一定程度上降低了河流流量资料的使用价值和精度标准。针对误差来源,提出了减少水深测量误差的具体建议。     

三峡临时船闸3号坝段位移场时空分布模型

以空间多个测点的观测资料为依据，引入测点坐标而建立的时空分布模型可动态监测任一组荷载时的坝体位移场，当固定坐标时该模型就演变为测点的监测模型。应用上述场理论，用线弹性、粘弹性有限元数值计算方法建立三峡临时船闸３ 号坝段梁挠曲线的时空分布模型     

二滩水电站1号泄洪洞水力特性与掺气减蚀的三维数值模拟

基于VOF法和k-ε紊流模型,对二滩1#泄洪洞进行了全流道三维数值模拟计算,获得了泄洪洞的流场及速度场、压力分布、水相分布及空腔、流速矢量等水力特征参数。计算结果表明:在原有体型通气孔侧墙部位,水流掺气不充分,出现局部负压,是造成该部位发生空蚀破坏的主要原因。本文所采用的数值模拟模型计算可以成为研究泄洪洞水力特征和掺气减蚀的一种方法。     

Estimating discharge in gravel‐bed river using non‐contact ground‐penetrating and surface‐velocity radars

Discharge measurement is a critical task for gravel‐bed channels. Under high‐flow conditions, the elevation of the riverbed changes significantly by intensive torrential flow. The stage–discharge relations commonly used for stream discharge estimation may no longer be adequate. The contact‐type velocity measuring is also subject to measurement errors and/or instrument failures by the high‐flow velocities, driftwood, stumps, and debris. This study developed a new real‐time method to estimate river discharge in gravel‐bed channels. A systematic measuring technology combining ground‐penetrating radar and surface‐velocity radar was employed. The rating curves representing the relations of water surface velocity to the channel cross‐sectional mean velocity and flow area were established. Stream discharge was then deduced from the resulting mean velocity and flow area. The proposed method was examined in a steep gravel‐bed reach of the Cho‐Shui River in central Taiwan. The estimated stream discharge during three flood events were compared to the prediction by using the stage–discharge relation and the index‐velocity method. The proposed method of this study is capable of computing reasonable values of discharge for an entire flood hydrograph, whereas the other two methods tend to produce large extrapolation errors. Moreover, when the computed discharge is used in 2D flood flow simulation, the proposed method demonstrates better performance than the commonly used stage–discharge and index‐velocity methods.     

基于垂线流速模型的雷达法断面流量测流精度分析

利用雷达多普勒流速仪进行测流是目前成本较低的实时自动测流方法。传统的雷达多普勒流速仪获得断面单条垂线上的表面流速,一般采用代表流速法建模计算断面流量,导致水位变幅剧烈的断面测流误差较大。本文基于表面流速数据的垂线法测流模型,采用雷达式二合一传感器获得断面的垂线表面流速和水深实测数据计算断面流量,并以新田水文站断面测流为例,与缆道流速仪法的测流数据结果进行对比验证。结果表明垂线平均流速相对误差在 5%以内的合格率达到 75%,断面平均流速相对误差和断面流量相对误差在 5%以内的合格率均达到 67%,故仅需布设两个雷达测速仪即可达到相对误差小于 5%的高精度测流,在自动测流站中有较好的应用。     

NUMERICAL INVESTIGATION ON EXTRUDATE SWELL FOR VISCOELASTIC FLUID： USING MAXWELL MODEL

The numerical investigation on extrudate swell through capillary die for viscoelastic fluid characteried by integral-type Maxwell constitutive equation was conducted by employing the finite element method with the calculation of viscoelastic extra stress in the conventional finite element. The method of avoiding singularity was also adopted by integrating the strain history of the Gauss points for each element near the wall and the free surface. The convergence solutions at high Weissenberg number can be obtained by using the appropriate methods to reduce errors and improve the speed of convergence of the calculation, which include adding a relaxation factor of velocity in iteration process, or enlarging the reference viscosity, or reducing the elapsed time. The highest Weissenberg number obtained here is up to 3. 8, while the solution at the Weissenberg number of 3. 75 was given in the previous work with similar extrudate swell ratio and the exit pressure drop by using differential Maxwell model with Elastic-Viscous Stress Split (EVSS) combined with Streamline Upwind Petrov-Galerkin (SUPG) scheme. The calculations indicated that the method of dealing with integral consti- tutive equation introduced in this paper is suitable in simulating viscoelastic flow characterized by integral constitutive equation at high elastic level.     

A NEW NUMERICAL METHOD FOR GROUNDWATER FlOW AND SOLUTE TRANSPORT USING VELOCITY FIELD

A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.     

基于液态缩尺模型的大空间下送中回分层空调回风汇流速度场研究

选择某大空间实型建筑,根据相似理论建立液态模型实验台,研究大空间下送中回分层空调回风流场的汇流特性。论文利用二维微元汇流叠加方法获得汇流速度理论公式,利用粒子图像测速技术PIV(Particle Image Velocimetry)拍摄回水流场,获得其速度矢量信息;实验发现计算得到回风流场的理论速度值与实验速度值存在较大的偏差,对二维汇流速度理论公式修正后,平均相对误差减少到8.5%。论文最后通过相似比例提出大空间下送中回分层空调回风二维汇流速度半经验公式,这为大空间建筑下送中回热环境研究提供了理论参考。     

A NEW NUMERICAL METHOD FOR GROUNDWATER FIOW AND SOLUTE TRANSPORT USING VELOCITY FIELD

A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.     

水文测验中两种测速垂线精简算法比较研究

随着中小河流治理项目的推进,改革水文测验方式,探索测流方式方法技术创新势在必行。本研究依托南京信息工程大学学生水文测验教学实习过程中组织开展的2次测速垂线优化精简实验,收集了渔梁水文站2次多测速垂线流量测验数据,针对原精简算法在流量误差最小的寻优过程中可能删去最有代表性的垂线这一问题,设计了直接寻求流量误差最小的测速垂线组合的新算法,并深入分析了两种精简算法对流量误差的影响。结果表明:测站目前采用的常测法选取的13根固定垂线代表性较好,流量测验精度较高;对比原算法,新的垂线精简算法在相同垂线数目下,流量误差更小,测验精度更高;由新算法,特殊水情下单垂线测流可考虑将垂线位置布设在起点距84 m处;流量相对误差大小随着优选垂线数量的增加呈指数递减规律。本研究所提的垂线精简算法有助于提高实验的精度,可为基层水文站开展垂线精简分析工作,进行测流方式改革提供参考。     

VOF方法模拟水面振荡流场

应用VOF(Volume of Fluid)方法结合不可压缩流体的N-S方程和连续性方程对矩形水池中的水面振荡流场进行数值模拟.采用共轭剩余法结合差分法求解N-S方程和连续性方程,采用施主-受主法求解流体体积函数控制方程.计算得到一个振荡周期内典型时刻矩形水槽水面振荡流场分布情况并与理论分析结果进行比较.并将计算得到的...     

天然河道一维非恒定流数学模型

天然河道水流计算中，洪水漫滩时横向流速分布极不均匀，直接用一维非恒定流方程进行模拟会产生较大误差，以前的处理方法其假定与实际差距较大，作者对此作了一些探索性研究，将横断面划分成若干个子断面，动量方程中的动量项取为各子断面动量之和，从而消除了横向流速分布不均匀的影响，并对渭河下游一次洪水过程进行了计算。     

H网格数值求解粘性不可压缩叶型绕流

本文用H型网格和特殊的差分格式数值求解了粘性不可压缩叶型绕流。为了加速速度和压力迭代的收敛性成功地引入了质量流量校正法。