Drag reduction using riblets downstream of a high Reynolds number inclined forward step flow

Micro-riblet is an efficient passive method for controlling turbulent boundary layers, with the potential to reduce frictional drag. In various applications within the transportation industry, flow separation is a prevalent flow phenomenon. However, the precise drag reduction performance of riblets in the presence of flow separation remains unclear. To address this, an inclined forward step model is proposed to investigate the interaction between riblet and upstream flow separation. The large eddy simulation (LES) method is applied to simulate the flow over geometries with different step angles and riblet positions. The results show riblets still reduce wall frictional resistance when subjected to the upstream flow separation. Remarkably, as the angle of the step increases from 0 degrees to 30 degrees, the drag reduction experiences an increment from 9.5% to 12.6%. From a turbulence statistics standpoint, riblets act to suppress the Reynold stress in the near-wall region and dampen ejection motions, thus weakening momentum exchange. Quadrant analysis reveals that with the augmentation of flow separation, the Q2 motion within the flow field intensifies, subsequently enhancing the riblet-induced drag reduction. Moreover, the position of the rib lets has a significant impact on the pressure drag. Riblets close to the point of separation enhance flow separation, altering the surface pressure distribution and thus increasing the resistance. The results reveal that when the riblets are positioned approximately 160 riblet heights away from the step, their effect on the upstream flow separation becomes negligible. The precise performance of riblets under complex flow conditions is important for their practical engineering application

Influence of the topological structures of the nose of high-speed maglev train on aerodynamic performances

In the past few years, considerable attention has been paid to high-speed maglev train in the field of rail transit. The design speed of the high-speed maglev train is 600km/h, which is significantly higher than that of the high-speed train. With the increase in operating speed, high-speed maglev trains have higher requirements for aerodynamic shape. Superior performance, the beautiful aerodynamic shape is an important direction for the development of high-speed maglev trains. Based on the Vehicle Modeling Function (VMF) method, the current research has developed a parametric shape design method suitable for the aerodynamic shape of the maglev train s nose. This method can obtain different topological structures of the high-speed maglev train s nose. The current research uses this method to generate four maglev train noses with large appearance differences and uses these train noses to construct four simplified high-speed maglev models. Then this study numerically analyzes the flow fields of different train models and compares the differences in aerodynamic performance including aerodynamic drag, aerodynamic lift and wake characteristics. The Q-criterion is used to study the vortex structure and mechanism of different train wake regions, and the vortex propagation process is studied by turbulence kinetic energy (TKE). Studying the difference in the aerodynamic force of different topological shapes will help to improve the aerodynamic performance of high-speed maglev trains. © 2021 American Society of Mechanical Engineers (ASME). All rights reserved

双层动车组列车风特性研究

列车行驶过程中会诱导周围空气流动形成列车风，较大强度列车风会危及行人和轨道旁工作人员的安全，甚至会卷起附近的货物和杂物。通过数值模拟的方法研究不同行驶速度的五编组双层车厢动车组周围的流场结构和列车风。结果表明：列车风主要由尾流区域涡脱落诱导产生，头车流线型区域、转向架等附属结构和地面效应对诱导列车风也有重要作用。列车周围靠近地面的区域受到附属结构和地面效应直接影响，列车风强度大于远离地面的区域。依据TSI 130—2014,行驶速度在200 km/h及以下速度级的双层车厢动车组符合列车风风速的安全标准，行驶速度250 km/h及以下速度级的双层车厢动车组符合车头压力脉冲要求

沟槽微结构尺寸对高速列车横风特性影响研究

随着列车运行速度的不断提升,气动效应对列车运行安全性产生的影响越来越突出。目前针对高速列车横风效应的研究通常假定列车表面光滑,实际上列车表面是非光滑的,边界层内的流动特性有所不同。利用微结构进行非光滑表面设计的新型技术手段可能改善高速列车在横风条件下的气动性能。以在车顶加设矩形条带组的方式,对1∶25比例的列车模型进行局部非光滑设计;采用改进的延迟分离涡模拟(IDDES)方法对横风作用下光滑表面和粗糙表面的列车模型进行气动性能模拟。结果表明,与光滑模型相比,粗糙模型下的侧向力系数和倾覆力矩系数分别降低了3.71%和10.56%。选取条带的宽度、高度和长度为设计变量,基于正交试验设计方法设计不同的数值模拟方案,利用方差分析和极差的方法探索矩形条带几何参数与列车侧向力和倾覆力矩间的关系,给出条带外形设计的优选方案。本研究可为横风作用下如何提升高速列车的气动性能提供理论依据

Robust optimisation of the streamlined shape of a high-speed train in crosswind conditions

Traditional deterministic aerodynamic optimisation cannot consider environmental uncertainty, which may lead to sensitivity issues. The present study proposes a robust design framework for the aerodynamic optimisation of high-speed trains, which accounts for the uncertain wind and its impact on crosswind stability. In this framework, a variance analysis method based on the Non-Intrusive Polynomial Chaos is proposed to determine the deformation area, and a parametric model is subsequently established. The Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is used as the optimiser to minimise the mean and variance of the aerodynamic response. The mean and variance can be quickly predicted by an uncertainty analysis approach combining Monte Carlo simulation and Kriging model. The framework is then applied to the optimisation of a high-speed train under crosswind. The results of the robust optimisation are compared with those of the baseline geometry and deterministic optimisation. The mean and variance of the rolling moment under crosswind are reduced by 2.26% and 3.37% respectively after optimisation, indicating that the performance and robustness are both improved. The proposed framework is effective for the engineering design of high-speed trains and can also provide a reference for the robust design of other aerodynamic shapes

长航程水下滑翔机

本实用新型属于水下滑翔机领域，具体地说是一种长航程水下滑翔机，采用鱼雷式外形模块化设计,包括艏部舱段、姿态调节舱段、传感器舱段、能源舱段、浮力调节舱段、艉部舱段及水平翼，艏部舱段搭载高度计用于滑翔机水下避障，姿态调节舱段安装俯仰调节装置，用于调整水下滑翔机俯仰角，传感器舱段搭载探测传感器采集海洋数据，能源舱段搭载高能量密度电池提升续航能力，浮力调节舱段安装浮力调节装置，通过改变载体的排水体积实现升沉运动，艉部舱段安装有转向装置用于调整滑翔机航向，组合天线用于载体定位与通信，各舱段由内部拉杆依次连接，水平翼固定在能源舱段两侧。本实用新型具有长续航能力、功能性强、高可靠性、结构紧凑、便于装配及维护

Formation control method for underwater gliders

本发明涉及一种水下滑翔机的编队控制方法及系统，包括利用滑翔机自身数据和感知的流场数据进行滑翔机状态估计，用于多水下滑翔机编队控制；结合多机器人协同路径跟踪，用于多水下滑翔机协同速度控制和多水下滑翔机航点生成；调整多水下滑翔机组成的多边形位置关系及状态，用于输出多种编队控制行迹。本发明利用三台水下滑翔机进行三角形编队控制试验，试验测试的编队功能包括编队定向航行、顶点跟踪、中心跟踪、队形缩放、队形旋转、收敛控制和队形随动等，以及两种或多种功能组合，取得了正三角形编队的实际与期望边长误差标准差控制在1KM范围内，队形跟踪误差小于0.5KM的良好效果

一种水下滑翔机远程程序升级的方法及设备

本发明属于水下机器人电控系统领域，具体说是一种水下滑翔机远程程序升级的方法及设备。本发明包括以下步骤：1)接收更新指令：水下滑翔机收到通过无线传输的更新程序指令；2)应用程序流程：设置接收应用程序位置，启动接收程序写入相应的Flash；接收完成后进行数据校验；检验数据无误后，修改当前应用程序位置标志位，写入Flash保留区后系统进行重启；否则，返回启动接收程序写入相应的Flash的步骤；3)引导程序流程：设备重启后，引导程序通过查询Flash保留区，设置应用程序首地址并跳转相应的应用程序，实现程序升级。本发明的优点在于，主要升级程序在用户程序中，而跳转程序只负责跳转，大大减少了跳转程程序的负担，有效的提高了可靠性

水下机器人用机械式通断电开关

本实用新型涉及一种水下机器人用机械式通断电开关，开关底座密封安装于水下机器人舱壁上，开关底座的一端内部螺纹连接有开关旋钮，开关旋钮的一端与开关底座的一端内部之间形成螺旋副，开关旋钮的另一端螺纹连接有导通铜柱绝缘件，导通铜柱的一端与导通铜柱绝缘件螺纹连接，另一端为接触端；开关底座的另一端内部螺纹连接有触点电极绝缘件，触点电极绝缘件上安装有多个在断电状态互不导通的触点电极，各触点电极的一端围成供导通铜柱插入的空间，每个触点电极的另一端均预留有用于焊接线缆的焊接点。本实用新型工作可靠、使用寿命长，通断电操作方便，最大深度可以应用于全海深，可以广泛适用于各类水下机器人

Aerodynamic-Aeroacoustic Optimization of a Baseline Wing and Flap Configuration

Optimization design was widely used in the high-lift device design process, and the aeroacoustic reduction characteristic is an important objective of the optimization. The aerodynamic and aeroacoustic study on the baseline wing and flap configuration was performed numerically. In the current study, the three-dimensional Large Eddy Simulation (LES) equations coupled with dynamic Smagorinsky subgrid model and Ffowcs-William and Hawkings (FW-H) equation are employed to simulate the flow fields and carry out acoustic analogy. The numerical results show reasonable agreement with the experimental data. Further, the particle swarm optimization algorithm coupled with the Kriging surrogate model was employed to determine optimum location of the flap deposition. The Latin hypercube method is used for the generation of initial samples for optimization. In addition, the relationship between the design variables and the objective functions are obtained using the optimization sample points. The optimized maximum overall sound pressure level (OASPL) of far-field noise decreases by 3.99 dB with a loss of lift-drag ratio (L/D) of less than 1%. Meanwhile, the optimized performances are in good and reasonable agreement with the numerical predictions. The findings provide suggestions for the low-noise and high-lift configuration design and application in high-lift devices