汽车模型风截面测量中的图像处理技术

利用现代光力学方法进行汽车模型风截面面积的测量 ,在满足大景深和大视场的同时 ,整个系统的相对精度能达到± 1‰的要求 .对汽车模型风截面测量系统中的核心部分———“数字图像信号采集及分析处理系统”中有关风截面计算的三个关键算法进行了重点阐述 。

光力学法在汽车模型风截面测量中的应用

本文在满足大景深、大视场和高精度的同时,利用现代光力学方法首次实现了汽车模型风截面的非接触、全场、实时测量,并研制出了具有独创性的“汽车模型风截面光学式实时测量装置”。对桑塔纳2000型轿车1/4模型进行了风截面测试,并将本文结果与德国斯图加特大学汽车风洞实验室中的结果进行了对比,由此证明该法是成功的。

大截面尺寸风管快速连接施工技术

为解决传统角钢法兰风管成本高、施工速度慢和共板法兰风管在中高压系统中漏风量大的问题,本文提出一种采用螺栓连接的增强型共板法兰连接方法。该方法将普通共板法兰风管弹簧夹连接形式调整为共板法兰增加螺栓固定的形式,能够有效提高大截面风管连接强度、刚度。同时研究了风管预制加工设备与运输方法,降低了施工成本,提高了施工效率。

大截面风管安装结构优化及变形控制研究

针对超过规程限值的大截面风管在设计和施工中遇到的问题仍没有完善的解决方法,笔者以实际工程为依托,主要探讨了大截面风管的吊点布置和内支撑方案选择问题,并对内支撑和吊杆的稳定性进行了验算,最后通过通用有限元软件ANSYS对风管变形和应力分布进行了数值模拟,验算结果与实际的测量结果很贴近.

带内支撑的超宽大截面风管阻力特性研究

在需要输送大量空气且对层高有一定要求的场合,超宽大截面风管的应用越来越多,但是在设计和施工方面,并没有相应的参考依据。为此,结合此类风管的强度要求及结构特点,提出了集板面加强筋、套管内支撑为一体的加固吊装方案,并采用理论分析、CFD模拟和试验测试的方法,对带有内支撑的超宽大截面风管的阻力特性进行了研究,定量分析了风管宽高比、加强筋以及内支撑对摩擦阻力和局部阻力的影响。结果表明,这些特殊结构对风管的阻力有较大的影响,并给出了相应的计算方法和修正依据。

变截面风管空调房间气流组织的数值模拟

为使主风管的风速经过各支风管后仍保持一致,通常使用改变风管截面积的方法。本文以变截面积风管的空调房间为研究对象,各支风管设为送风口,利用计算流体动力学(Computational Fluid Dynamics,CFD)方法,建立空调房间有孔板和无孔板的物理模型,并对有孔板情况进行设计风量和两倍设计风量的模拟对比。通过流场分析,发现气流均匀性要求较高的场合宜采用孔板送风,孔板作用体现在其对送风气体运动轨迹的限制,对上下部区域速度进行调整,使得工作区域风速降低,消除风速不利影响,送风速度越大,该作用越明显。

大截面风管装配式施工管理

采用BIM技术对综合枢纽暖通工程进行三维建模,可以大大提高设计、施工效率和质量,有效协同优化各专业管线,解决各专业碰撞问题。通过拆分大截面风管、标注管段并编码,可以实现整个风管系统预制、运输、拼装等环节的验收及交接状态追踪,从而提高施工效率和质量。此外,根据管道长度进行地面管道组装、抬升至施工高度进行高空拼接和固定,可确保风管工程的施工质量和安全。最后,采用风管工厂内预制、现场装配化施工的方法,可以合理穿插加工和安装工序,从而保障大型综合枢纽工程机电施工的有序进行和优质高效。

基于散射中心的风电机RCS数据压缩重构

为解决风电机对雷达信号干扰的实时处理问题,必须将数据量超过十亿量级的风电机全姿态雷达散射截面(Radar Cross Section,RCS)数据进行有效压缩重构。针对传统阈值离散傅里叶变换(Threshold Discrete Fourier Transform,TDFT)由于阈值选取困难而压缩重构效果不佳的问题,避开阈值的选取问题,基于电磁散射理论,提出了一种采用风电机散射中心参数集表征大量RCS数据的思想。基于几何绕射理论散射中心模型,采用总体最小二乘-旋转不变技术信号参数估计(Total Least Squares-Estimated Signal Parameters via Rotational Invariance Technique,TLS-ESPRIT)法,求解了由风电机RCS数据所构成的两个子向量间的旋转因子矩阵,进而获取了风电机一维散射中心参数集,最终实现风电机RCS数据的有效压缩重构。以金风77/1500型风电机为算例。结果表明,与TDFT相比,在同一重构误差范围内,基于散射中心的压缩重构方法数据压缩比最高可达31.25。

自行车运动中长距离与短距离骑行技术差异的生物力学分析

一个自行车运动员要创造良好的运动成绩,首先要掌握正确的骑行姿态。轻松蹬踏,自如操车,可避免不必要的肌肉紧张,降低能量消耗,保证力量和技术得到充分的发挥。 根据竞赛规则,多数在赛车场内进行的比赛距离短、强度大,骑行时肌肉、神经高度紧张;而公路比赛的特点则是进间长、距离长、平均强度低。由此可见,这两种比赛必然要求两种不同的技术。根据自己的运动实践,我认为骑车技术上存在的差异,主要体现在长距离骑行技术与短距离骑行技术之间的差异。本文讨论是在选择了合适的赛车的基础之上进行的。

A Physics-Based Dual-Frequency Approach for Altimeter Wind Speed Retrieval

The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study.

Repair wind field in oil contaminated areas with SAR images

In this paper,we compared the normalized radar cross section in the cases of oil spill,biogenic slicks,and clean sea areas with image samples made from 11-pixel NRCS average,and determined their thresholds of the NRCS of the synthetic aperture radar. The results show that the thresholds of oil and biogenic slicks exhibit good consistency with the corresponding synthetic aperture radar images. In addition,we used the normalized radar cross section of clean water from adjacent patches of oil or biogenic slicks areas to replace that of oil or biogenic slicks areas,and retrieve wind field by CMOD5.n and compare wind velocity mending of oil and biogenic slicks areas with Weather Research and Forecasting modeled data,from which the root mean squares of wind speed(wind direction) inversion are 0.89 m/s(20.26°) and 0.88 m/s(7.07°),respectively. Therefore,after the occurrence of oil spill or biogenic slicks,the real wind field could be repaired using the method we introduced in this paper. We believe that this method could improve the accuracy in assessment of a real wind field on medium and small scales at sea,and enhance effectively the monitoring works on similar oil or biogenic slicks incidents at sea surface.

Wind response of high-rise building in diversified inlets to construct wind turbine system on roof

Many skyscrapers have installed wind turbine systems to use new renewable energy. In particular, building an integrated wind power generation system by installing a wind power generator inside a building is an attractive method to secure safe energy. However, most studies have dealt with the efficiency of wind turbines and the response effects of wind induced vibration; space preparation for wind turbine installations has not been sufficiently considered. This work reviewed the shapes of openings where wind turbines can be installed in skyscrapers, and the characteristics of wind induced vibration responses occurring in the building with changes in cross sectional area. Nine wind power models were constructed to carry out the experiment. According to the experimental results, wind speed varies with shape of opening in the order of C-type>S-type>R-type. Moreover, wind speed increases as the area is reduced.

Vibration and flutter of wind turbine blade modeled as anisotropic thin-walled closed-section beam

Based on a variational asymptotic analytical model, vibration and aeroelastic stability of rotor blades modeled as anisotropic thin-walled closed-section beams are systematically addressed. The analysis is applied to a laminated composite construction of the circumferentially asymmetric stiffness (CAS) that produces bending-twist coupling. The vibration characteristics of composite beam are determined by the Extended Galerkin Method. The unsteady aerodynamic loads and centrifugal force are integrated with the classical aerodynamic model to deal with aeroelastic stability analysis. The influence of some related factors, ply angle, rotating velocity, and wind speed, is investigated. The paper gives methods of eigenvalue analysis and aeroelastic response, and gives the approaches to restrain classical flutter.