Three-dimensional tidal current numerical model of the Oujiang Estuary

The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.

A three-dimensional numerical calculation of the wind-driven thermohaline and tide-induced Lagrangian residual current in the Bohai Sea

On the basis of a three-dimensional weakly nonliear theory of Lagrangian residual current in the Baroclinic shallow seas, a diagnostic numerical calculation of wind-driven, thermohaline and tide-induced Lagrangian residual current in the Bohai Sea is made. The model involves the Richardson number in the eddy viscosity coefficient, wind, thcrmolialine and tidal effects in the focing terms. The runoff of the Huanghe River and a part of the Huanghai Warm Water coming from the Huanghai Sea through the Bohai Sea Strait is also considered. The velocity-splitting method is adopted. The wind-driven circu lation, thermohaline circulation and the tide-induced Lagrangian residual circulation are also obtained individually and analysed. The dynamics of the three main eddies in the Lagrangian mean circulation is discussed. Finally, the numerical result is partly verified with the observed data.

Numerical simulation of three-dimensional tidal current in the Bobal Sea

The model equations with tbree-dimensional, time-dependent, nonlinear Navier-Stokes equations are transformed by sigma-transformation.On the basis of the process splitting technique, the fluid flow problems are divided into two parts:the vertically-intopated equations (external mode) and the vertical structure equations(internal mace). The first set of equations being the propagation of the tidal weves and the ADI numerical scheme has ben chosen to solve them. Conerning the vertical structure equations, they are solved by means of leapfrog stepping procedure.The main features of the tide and associated tidal current in the Bohai Sea are examined with this 3-D model.To have a good reproduction of vertical structure, the column is divided into 10 layers and the M2 tidal current is computed in detail. The simulation reveal the spetial structure and some important characteristics of the tidal current of the Bohai Sea. The application of the 3-D madel to forecasting of the tidal current in the Bobal Sea has been Performed as an illustration.

Numerical Simulation of the Three-Dimensional Wave-Induced Currents on Unstructured Grid

By coupling the three-dimensional hydrodynamic model with the wave model, numerical simulations of the three- dimensional wave-induced current are carried out in this study. The wave model is based on the numerical solution of the modified wave action equation and eikonal equation, which can describe the wave refraction and diffraction. The hydrodynamic model is driven by the wave-induced radiation stresses and affected by the wave turbulence. The numerical implementation of the module has used the finite-volume schemes on unstructured grid, which provides great flexibility for modeling the waves and currents in the complex actual nearshore, and ensures the conservation of energy propagation. The applicability of the proposed model is evaluated in calculating the cases of wave set-up, longshore currents, undertow on a sloping beach, rip currents and meandering longshore currents on a tri-cuspate beach. The results indicate that it is necessary to introduce the depth-dependent radiation stresses into the numerical simulation of wave-induced currents, and comparisons show that the present model makes better prediction on the wave procedure as well as both horizontal and vertical structures in the wave-induced current field.

Persistent currents in three-dimensional shell-doped nanorings

The persistent current in three-dimensional （P × N2） nanorings as a function of the unit cell number （P）, the channel number （M =N2）, surface disorder （ζ）, and temperature （T） is theoretically investigated in terms of rotational symmetry. On the whole, the typical current increases linearly with √M but decreases exponentially with P, while wide fluctuations exist therein. In the presence of surface disorder, the persistent current decreases with ζ in the regime of weak disorder but increases in the regime of strong disorder. In addition, it is found that the persistent current in perfect rings decreases exponentially with temperature even at T 〈 T＊, while in most disorder rings, the typical current decreases slightly with temperature at T 〈 T＊.

基于改进WOA-MP算法的多普勒海流计回波信号频率估计研究

受海洋环境复杂干扰影响,多普勒式海流计的超声波回波信号易受干扰影响,包含多种频率成分,这给海流流速信息的解算带来困难。为解决多普勒海流计回波信号频率估计精度较差的问题,提出一种基于信号匹配追踪(MP)的频率估计方法,并融合改进型鲸鱼优化算法(MWOA)提高估计过程的效率。该方法利用混沌映射提升初始种群多样性,并引入自适应权重和非线性收敛因子提高算法局部寻优能力、搜索速度和求解精度。而后,对改进算法与其他优化算法进行对比测试,结果显示所设计改进算法在收敛速度和寻优能力上具有有效性和优越性。此外,通过对多普勒回波信号进行特征重构,开展MWOA-MP算法在噪声环境下的频率估计精度性能测试。在回波信号信噪比为–10 dB条件下,MWOA-MP算法相对传统方法抗噪声能力提高30%。与其他智能方法融合MP后的频率估计算法相比,MWOA-MP算法的估计误差在10 Hz以内,可满足多普勒海流计频率测量精度要求。

基于混合铁心的新型电流互感器研究

传统电流互感器铁心饱和会导致其二次电流波形发生畸变,进而可能影响电能计量的精度或引起继电保护设备错误动作,威胁电网的安全稳定运行。针对此类问题,提出了基于混合铁心的新型电流互感器(CCCT)。CCCT主要由混合铁心、二次绕组、二次电阻、磁场传感器与信号处理电路组成,其中混合铁心包含完整的内铁心与带气隙的外铁心,磁场传感器放置在外铁心的气隙中,其输出信号用于补偿发生畸变的二次电流。为验证该结构的有效性,进行了有限元仿真,制作了CCCT样机并进行了正弦交流电流、正弦半波电流、短路电流和直流电流的测量实验。有限元仿真与实验结果表明,CCCT在额定电流下的复合误差小于0.2%,稳态对称短路电流下的复合误差为2.04%,暂态短路电流下的峰值瞬时误差为4.25%,直流条件下输出与输入的拟合优度为0.999 9,既基本保留了传统电流互感器的测量精度,也具有良好的暂态响应特性与抗直流特性,可同时满足相关标准对测量、保护用电流互感器的精度要求,具备在实际工程中应用的潜力。

海流探测仪器与技术研究现状及展望

精准、实时的海流数据是海洋资源开发与利用、海洋科学研究等方面的重要输入参数之一。海流探测仪器按照测量原理主要分为机械式、电磁式、声学多普勒式和声学时差式4类传统海流计,以及当前结合了光纤传感等技术的新型海流计。在本文中,作者从探测原理、优缺点、应用领域、发展现状等方面对传统海流计与光纤类海流计进行了梳理与总结,展望了未来海流探测仪器的发展趋势,并提出了一种基于连续时差法的光致超声测流方法。旨在对海流计的开发与研究提供借鉴与参考,在增进海洋探测技术的发展、加快实施海洋强国战略中具有一定的意义。

基于动网格6DOF模型的框架式流速仪水力特性数值模拟与明渠测流速率常数预测

为分析明渠内框架式流速仪流场特性与运动姿态,同时对流速仪倍常数K和摩阻系数C进行率定,根据不可压缩流体流动的Navier-Stokes方程和SST k-ω湍流模型,结合VOF多相流模型,建立动态网格下的6自由度(6DOF)刚体动力学耦合数值仿真模型,对水冲击流速仪旋桨使之被动旋转过程进行了仿真,分析了流速仪在不同位置对流速仪倍常数K和摩阻系数C的影响规律。结果表明:采用动网格6DOF模型可以较好地模拟框架式流速仪在明渠的流动状态,仿真结果可靠性较高;通过对不同时刻转速与流速拟合曲线分析可知,流速仪位置不同会影响流速仪摩阻系数C,对流速仪倍常数K影响不大。研究结果可为进一步研究框架式流速仪优化和不同含沙水流条件下对流速仪的磨损提供参考。

基于时差法的低功耗超声波三维海流测量系统

声学时差海流计具有高精度、高采样率、无盲区和不受海洋散射条件限制的优点,目前国内尚无时差海流计系统样机以及核心部件(四声道双晶换能器)的报道。为了实现对海洋矢量流速的长期精确测量,设计并研制了基于时差法的低功耗超声波三维海流测量系统,构建了四声轴三维矢量流速测量模型,通过有限元仿真设计并制备了小体积异形异构V形双晶换能器。系统采用低功耗STM32L431和MSP4306288为主控芯片,由TDC-GP22高精度时间测量模块、换能器驱动电路、低功耗放大滤波电路、SD卡存储模块等组成测量电路,通过测量换能器4个声轴上的超声波飞行时间差,得到海水的三维矢量流速。系统采用低功耗硬件系统设计,配合软件低功耗管理降低系统功耗。经实际测试,所研制的三维海流测量系统具有测量准确、低功耗、存储方便等优点。

直流充电桩电能计量关键技术设计

针对当前直流(DC)充电桩电能计量存在计量效率低、误差大、电源纹波大、无法远程监控的问题,设计了充电桩计量电路。通过硬件乘法器级联原理实现三相交流有功功率的瞬时值硬件电路,能够快速获取交流(AC)有功功率在时域上输出的数据信息。将原始的多种信息输出变成单一的DC信号,为双通道模数转换器(ADC)同步测量提供了μs级别的AC有功功率信号。通过增量补偿控制输出模块对电网电压和实际输出电压的差值进行补偿,提高了充电桩测试电源的精度。DC充电桩能够远程无线通信,实现了多地区多客户端界面和现场操作终端界面的操作流程和数据的实时同步,大幅提升了DC充电桩电能计量能力。试验结果证明,该设计误差低、计量效率高。

圆筒形FPSO浪流仪自动升降装置撬装化设计研究

针对圆筒形FPSO浪流仪自动升降装置的安装效率和操作便捷性问题,设计一种撬装化系统,旨在提升设备的安装效率、操作便捷性及使用寿命,以满足深海油气资源开发的实际需求。通过深入研究圆筒形FPSO浪流仪自动升降装置的工作原理和结构特点,提出一种撬装化设计方案,同时采用结构强度分析和疲劳分析来验证设计的可行性及安全性。研究结果表明,撬装化设计方案可以有效提高圆筒形FPSO浪流仪的安装效率和操作便捷性,同时满足工程安全要求,保障设备的使用寿命。研究为圆筒形FPSO浪流仪安装提供了一种有效的解决方法,具有显著的工程实用价值和广泛的应用前景。

数据驱动的电能计量装置电流积分法差错电量估算误差评估

为了减少电能计量装置故障期间使用电流积分法计算差错电量的计量误差,该文引入配对t检验和Bootstrap抽样方法,科学计算差错电量校正系数。首先,基于配对t检验的方法,在小样本集的基础上,检验传统电流积分法计算得到的正常时间段预估用电量与实际用电量之间是否存在显著差异;然后,利用基于滚动Bootstrap抽样的方法得到大样本数据集,计算两者比值得到预估用电量的校正系数;最后,通过计算实验验证了上述流程。结果表明,小样本配对t检验能够减少差错电量计算工作量,大样本估算能够使校正系数的估算更具可靠性,减少估算误差。

直流电能表计量信号自适应降噪方法

直流用电负荷包含DC/DC变换器等电力电子器件,非线性特性显著,导致直流输出端电压、电流信号存在大量纹波,需通过滤波降噪处理提升直流电能计量的准确性。针对现有的滤波降噪方法参数设置缺乏优化、滤波降噪效果尚待提升问题,提出了基于自适应变分模态分解与小波阈值去噪相结合的直流电能表计量信号降噪方法。建立输出端直流电压、电流信号变分模态分解的参数最优化模型,并联合互信息分析,实现原始信号的有效模态分量与噪声模态分量的自适应区分。在此基础上,建立以信噪比、均方根误差、平滑度、相关系数复合评价指标最优的小波阈值去噪参数最优化模型,实现噪声模态分量的最优滤波降噪。通过实测数据计算分析,验证所提方法的有效性。

基于红外测温技术的电能表电流采样回路失流故障分析

研究基于红外测温技术的电能表电流采样回路失流故障分析方法,保证电能表安全运行。构建电压火线断线故障与电流采样回路故障模型,分析电能表电流采样回路失流故障原因,以此为基础,利用红外热成像原理采集电能表电流采样回路、大气以及周围物体的辐射能量,生成展现电能表电流采样回路温度的二维红外图像,为后续电能表电流采样回路失流故障定位提供图像信息;采用灰度差异加成法处理多层级红外二维图像,结合插值算法组建三维图像,依据三维图像中电能表电流采样回路与周围状态的轻微差异定位失流故障位置。实验表明,该方法能够实时监测电能表电流采样回路的温度,直观发现问题,可靠且准确地定位电能表电流采样回路失流故障位置。

导轨式多回路计量电能表

介绍了一种多路计量三相电能表,电能表采用外置的开口电流互感器,通过RJ12端子连接在电能表上。电能表最多可以计量4路三相四线电能。电能表采用导轨式DIN-35安装方式,可以轻松安装在配电箱内。电能表具有RS485端口,支持Modbus-RTU协议,可以远程方便采集电能表数据。

电能表复电装置的研制

智能电能表现场编程须满足主回路电压达到78%以上,因此在主回路无电压时,无法实现电能表的现场编程或拆旧表计时读取表底度。对此,部分技术人员会在现场其余回路搭接电压,启动电能表完成编程,此种情况下极易造成人身或设备的安全事故。为此,研制一款便携式复电装置能够输出50、100、220 V 3个档位的交流电压,具备过流、过压安全保护功能,提升现场作业安全和工作效率。

大电流圆表的设计与实现方法

介绍了设计与实现大电流圆表的方法。通过确定设计需求,选择合适的测量方法,设计电路,选择显示器件,设计外部接口,进行硬件实现、软件编程、测试和校准、优化和改进及批量生产等步骤,实现了一种功能齐全、精确可靠的大电流圆表,为工程师和研究人员提供全面指南,以帮助他们设计和实现大电流圆表,并应用于相关领域。

电波流速仪在赵石窑水文站渠道的应用分析

赵石窑水文站渠道位于横山区响水镇无定河左岸,常年平均流量六点多立方米每秒,下游一公里有发电站一座,水流流态常年受其影响,水位变幅较大。平常测验使用的是旋浆式流速仪进行测验,由于北方地区泥沙大,漂浮物多,旋浆式流速仪易被水草缠绕,对测验影响较大,且测验时间较长。而电波流速仪属非接触水面式的,测验时间短且安全。对赵石窑水文站渠道电波流速仪法和旋浆式流速仪法进行比测分析,率定电波流速仪的水面系数。

计量站来油分配偏流影响因素分析

为了研究计量站来油分配规律,明确并联管路“偏流”工况的影响因素,利用流体软件Fluent对进站管路流量分配均匀性的影响因素进行理论研究和数值模拟,分别改变分配管间距、入口流速、入口管直径、分配管长度和分配管管径与初始模型软件计算数据进行对比,研究不同条件对流量分配均匀性的影响。研究结果表明:相同的条件下,适度增大分配管管间距有利于提高流体在管道内流动均匀性;适度降低流体在进站管道中流速,可提高流量分配均匀性;增加分配管长度可改善流量分配均匀性;适度减小集管和分配管的直径可使流量分配更加均匀。