自制AppleⅡA/D、D/A卡

在联机状态下微机应用于物理实验常常要将各种物理系统经过适当的传感器转换成模拟电压,然后经过模数转换器 ADC 转换成数字量输入计算机进行分析处理.计算机输出的信息也需要经过数模转换器 DAC 将数字量转换成模拟电压以便送到示波器显示或控制其他仪器.本文介绍两种用于 Apple Ⅱ     

非对称空间外差光谱仪风场模拟探测实验研究

针对已搭建的非对称空间外差光谱仪开展地基风场模拟探测研究,验证该仪器进行中高层大气风场的探测精度水平.介绍了非对称空间外差光谱技术进行风场探测的基本原理以及研制的光谱仪基本性能参数,设计了风速模拟装置开展风场模拟探测实验,并对风速模拟过程中电机转速、安装机械角度、转盘半径测量值、光线入射角度等不确定因素进行了分析和计算,该装置模拟的理论风速误差不高于1.3%,能够满足风场模拟探测验证要求.利用该风速模拟装置并通过调节不同电机转速实验,获得了模拟风速在34.19~78.63m/s内的24组测量数据,模拟覆盖了中高层大气风速范围,对测量数据进行误差修正及风速反演处理,非对称空间外差光谱仪实测风速结果与理论模拟风速对比后得出了风速误差标准差3.28m/s的风速探测精度,有效验证了非对称空间外差光谱技术开展风场探测具有相位灵敏,精度高等特点.     

机动车空气动力测试风洞的声学设计

测试、鉴定并研究高速机动车对环境及在车内所产生的噪声，必须有“安静”的风洞，抑制风洞内的气流噪声，将它的本底噪声降低到车辆噪声以下，测试大厅中有足够低的以上获得应有的自由声场范围，所有的声学处理措施不影响风洞的空气动力性能；吸声构件中不含矿物性纤维材料；具有相应的阻燃性能并易于清洁，本文介绍了满足以上所有要求的斯图加特大学空气动力实验室风洞的声学设计和所采用的新型吸声材料，给出了构造大样及实测结果     

空气阻力系数测试仪

为了定量研究固态物体与空气做相对运动时,物体的受力情况与形状和相对速度的关系研制了空气阻力系数测试仪.该仪器构建了一个小型的风洞,可以随意调节风洞风速的大小,并根据流体力学中的伯努利方程采用孔板法来定量测定风速,再设计了多种不同形状的物体效应物,用力传感器来测出它们在气流中所受的阻力,由此求得不同形状物体的相对阻力系数.     

风沙流中颗粒相浓度和粒度的瞬态同步测量

本文基于激光衍射技术提出了一种新的浓度测量的改进方法。该方法可以同时获得测量颗粒的浓度和粒径分布。基于这一测量方法,通过对大型风洞风沙两相流系统中不同风速,高度条件下颗粒浓度和粒径测量,获得了跃移颗粒的空间结构信息。结果显示,颗粒浓度随来流风速线性增加,且在近床面区域内来流风速对颗粒粒径具有选择性。     

基础实验试题A-2和A-3:毛细管中液体的流动及风洞实验

介绍了第7届全国大学生物理实验竞赛基础实验试题A"流体的流动"中的第二部分"毛细管中液体的流动"和第三部分"风洞"的内容,并给出了参考答案及竞赛结果分析.第二部分试题包括基于泊肃叶定律的倾斜毛细管测量液体黏度及根据毛细管中液体流动的物理状态与雷诺数的关系进行的实验拓展.第三部分涵盖研究乒乓球在风洞内受到的摩擦阻力与风速...     

滑线变阻器的传感作用

传感器能将所感受到的物理量(如力、热、光、声等)转换成便于测量的量(一般是电学量)．其工作过程是通过对某一物理量敏感的元件将感受到的信号按一定规律转换成便于利用的信号，经相应的仪器进行处理，就可以达到自动控制等目的．如常用的光电传感器、热电传感     

风洞中投弹运动的三维高速立体摄影测量

高速立体摄影测量可获得运动物体的三维信息。我们对风洞中飞机投弹的模拟试     

热带气旋大气边界层风洞模拟

在风洞中正确复现大气边界层特性是保证风洞实验结果准确度的必要条件。本文利用三角形尖劈和粗糙元配合对风洞内热带气旋大气边界层模拟进行了研究,生成了较好反映热带气旋风特性的大气边界层,平均速度和湍流强度廓线与设计值吻合较好,同时提出了用于热带气旋大气边界层内的风力机模型的设计要求。     

几种传感器的应用举例

传感器是把非电物理量(如位移、加速度、压力、温度、流量、声强、光照度等)转换成电学量(如电压、电流等)的一种元件．传感器输人的是非电物理量X，输出的是电学量Y，如图1所示．将非电物理量转换成电学量之后，测量比较方便，能够用于电路控制，而且能输入电子计算机进行处理．     

Numerical simulation and experimental validation of multiphysics field coupling mechanisms for a high power ICP wind tunnel

We take the established inductively coupled plasma(ICP) wind tunnel as a research object to investigate the thermal protection system of re-entry vehicles. A 1.2-MW high power ICP wind tunnel is studied through numerical simulation and experimental validation. The distribution characteristics and interaction mechanism of the flow field and electromagnetic field of the ICP wind tunnel are investigated using the multi-field coupling method of flow, electromagnetic, chemical, and thermodynamic field. The accuracy of the numerical simulation is validated by comparing the experimental results with the simulation results. Thereafter, the wind tunnel pressure, air velocity, electron density, Joule heating rate, Lorentz force, and electric field intensity obtained using the simulation are analyzed and discussed. The results indicate that for the 1.2-MW ICP wind tunnel, the maximum values of temperature, pressure, electron number density, and other parameters are observed during coil heating. The influence of the radial Lorentz force on the momentum transfer is stronger than that of the axial Lorentz force. The electron number density at the central axis and the amplitude and position of the Joule heating rate are affected by the radial Lorentz force. Moreover, the plasma in the wind tunnel is constantly in the subsonic flow state, and a strong eddy flow is easily generated at the inlet of the wind tunnel.     

利用干涉成像光谱技术测量大气风场

以大层大气中的气辉（极光）为被探测源,利用干涉成像光谱技术和电磁波的多普勒效应对上层大气风场进行测量,分析和计算了大气风场的速度和温度,并就被探测源和探测器之间的相对速度与其连线成任意角时的情形进行了讨论。采用计算机模拟,分析了大气风场的测量效果。     

光学信号互相关法烟气流速测量的研究

工业环境中的烟气流速测量是一个很重要的问题。研究了利用抗干扰能力强、能适应恶劣环境的非介入式的光学信号互相关技术测量烟气流速。利用光学传感器获取由烟气造成的光学闪烁信号,通过高性能数据采集卡进行数据采集和A/D转换,在计算机上编制软件,对由烟气造成的光学闪烁信号进行了互相关处理,求得了烟气流经上游和下游传感器的渡越时间,从而计算出了烟气流速值。通过风洞实验,比较了该方法与传统的皮托管法的测量结果,分析了流速反演方法存在的问题及解决方法。在此基础上获得了较为满意的结果。     

Interference image spectroscopy for upper atmospheric wind field measurement

Based on the observation of natural airglow and auroral visible emission lines in the upper atmosphere as the explored source, we have surveyed the upper atmosphere wind field through interference imaging spectroscopy coupled with the Doppler effect of electrical and magnetic waves. The velocity and temperature of the upper atmospheric wind field are analyzed and studied. The survey theory and calculation formula of atmosphere wind field in all directions and multi-directions are presented when the relative velocity of the explored source to the detector and their linking line have an arbitrary angle. We also analyzed the effects of the measurement of the upper atmospheric wind field using computer simulation, and explained the reason why the auroral emission line is thought as Gaussian profile.     

Measurement and simulation of sand saltation movement under fluctuating wind in a natural field environment

Extensive research on the near surface movement of sand particles has focused on wind tunnel experiments, theoretical analysis, and numerical simulation of sand saltation under ideal and controllable conditions. Most field observations are results on the average rate of sand transport over some hours or the whole day. However, researchers found recently that the effect of turbulent characteristics of near surface wind in real atmospheric boundary layers on the sand transport rate was obvious. The turbulent characteristics would cause a significant discrepancy between field observation and simulation of sand transport rate. In this work, a field experiment in a real-time system was designed to synchronously measure physical quantities, such as fluctuating wind velocity in the near surface region, sand transport intensity, temperature, and humidity, with the frequency of 1 Hz, at two points on a homogeneous flat sand surface located in the Minqin area, which is between the edges of the Badain Jaran Desert and the Tengger Desert. The relationship between the saltation events and some physical properties, such as the fluctuating wind velocity, temperature, and humidity, was studied. On the basis of the field observation results, a numerical model was developed to simulate sand movement under the fluctuating wind. The overall features of the experimental measurements were reproduced by simulation.     

Aeolian transport layer

We investigate the airborne transport of particles on a granular surface by the saltation mechanism through numerical simulation of particle motion coupled with turbulent flow. We determine the saturated flux q(s) and show that its behavior is consistent with classical empirical relations obtained from wind tunnel measurements. Our results also allow one to propose and explain a new relation valid for small fluxes, namely, q(s) = a(u*-u(t))alpha, where u* and u(t) are the shear and threshold velocities of the wind, respectively, and the scaling exponent is alpha approximately 2. We obtain an expression for the velocity profile of the wind distorted by the particle motion due to the feedback and discover a novel dynamical scaling relation. We also find a new expression for the dependence of the height of the saltation layer as a function of the wind velocity.     

磁流体加速和磁流体加速风洞

高超声速飞行器对于更高飞行速度的追求，给地面风洞设备模拟能力提出了新的要求，磁流体加速成为一个重要突破方向.文章介绍了国内外在磁流体加速基本原理以及磁流体加速技术应用于地面风洞试验方面的研究工作.基于磁流体（magneto-hydro-dynanic，MHD）加速的高超声速风洞设备可以模拟高超声速飞行器的试验条件，复现超高速的飞行环境，是突破超高速飞行器再入研究地面试验模拟能力的关键技术，在航空航天领域具有重要的研究意义和应用前景.      

Electrical crosstalk-coupling measurement and analysis for digital closed loop fibre optic gyro

The phase modulation and the closed-loop controller can generate electrical crosstalk-coupling in digital closed-loop fibre optic gyro. Four electrical cross-coupling paths are verified by the open-loop testing approach. It is found the variation of ramp amplitude will lead to the alternation of gyro bias. The amplitude and the phase parameters of the electrical crosstalk signal are measured by lock-in amplifier, and the variation of gyro bias is confirmed to be caused by the alternation of phase according to the amplitude of the ramp. A digital closed-loop fibre optic gyro electrical crosstalk-coupling model is built by approximating the electrical cross-coupling paths as a proportion and integration segment. The results of simulation and experiment show that the modulation signal electrical crosstalk-coupling can cause the dead zone of the gyro when a small angular velocity is inputted, and it could also lead to a periodic vibration of the bias error of the gyro when a large angular velocity is inputted.     

Design and performance of a small-scale aeroacoustic wind tunnel

The D5 aeroacoustic wind tunnel at Beihang University is a newly commissioned small-scale closed-circuit wind tunnel with low turbulence intensity and low background noise. The wind tunnel is built to study both aerodynamic and aeroacoustic performance of aircraft components or scaled models. The wind tunnel has two types of test sections, the closed type test section is used for aerodynamic tests while the open type test section is mainly used for aeroacoustic experiments. Both types of test section are 1 m in height and 1 m in width, and the maximum wind velocity in the test section can be up to 80 m/s. An anechoic chamber is built surrounding the test section to provide the non-reflecting condition. This paper provides an overview of design criteria and performance of the small-scale wind tunnel. The layout of the wind tunnel and some critical design treatments to improve aerodynamic and acoustic performance are discussed in detail. Some experiments are conducted to verify the performance of D5 wind tunnel, results confirm that the turbulence intensity is less than 0.08% in the core of test section and the background noise is comparable with other aeroacoustic wind tunnels. A scaled simplified nose landing gear model is also measured as a benchmark test, results reveal that noise radiated from the model is adequately higher than the background noise for a wide frequency range and remarkably consistent with other results from literatures.     

基于风洞的设备健康管理与数据有效性判定平台研究

低速增压风洞是满足我国航空工业科技发展而建设的一座气动力重大基础试验设施。为了保障该设施的高效率和可靠地运行,以各机电设备、电气测控设备、机械装置为对象,根据其故障模式和故障特点选取合适的监测点,获取实时工作状态数据,再以数据为基础,进行状态监测、故障诊断、故障预测,实现预先性决策和针对性快速维修。基于OSA-CBM 体系构建的风洞健康管理系统,根据设备的运行状态,实现对试验数据的有效性进行实时判定,并实现了风洞装备由事后维修向视情维修转变;实现了装备从使用、维护、管理模式由分散式管理向集约式管理的转变;实现了装备系统故障诊、预测及判读从人工智能向机器智能的转变。