ExVis and wind tunnel experiment data

Visualization specialists and aeroscientists at NASA Ames collaborated in investigating how information technology can improve the aeronautical design process. The author discusses ExVis software tool created to support interactive display and analysis of data collected during wind tunnel experiments     

一种自动校准多风表的风洞检测试验装置

针对传统风表校准方式需多次手动调节风量、操作复杂、人工读数与绘图费时费力且校准精度低等问题,设计了一种自动校准多风表的风洞检测试验装置,介绍了该装置的结构及检测试验原理。试验结果表明,该装置风流稳定,可自动调节风量,操作简单,可1次校准多个风表,校准精度高,并能对校准结果进行记录、存储、处理,适合于低、中、高3档多风表自动校准。     

风洞测控技术展望

介绍风洞测控系统在工控技术、总线技术、嵌入式系统、数采系统、传感器技术等方面的发展。     

Exact solution for wind tunnel interference using the panel method

Wind tunnel wall interference effects on lifting and non-lifting bodies are computed here for incompressible two-dimensional flows. The flows around bodies under consideration are computed by a panel method using linearly varying vortex distributions. The method is regarded as an exact numerical method. Also to exactly compensate for the wind tunnel wall, we use the method of images of the complete body in the wind tunnel. The image system consists of two cascades which extend infinitely on both sides of the wind tunnel. Thus, the exact wind tunnel wall interference effects are obtained for circular and elliptic cylinders, NACA 23012, NACA 64A010 and NACA 0010 airfoils. The velocity distributions and lift coefficient variations are presented for different blockages. The effects of airfoil incidences and the relative proximity of the two walls are also investigated. The present analysis has given rise to some results which otherwise would not have been possible by earlier existing very approximate methods. Wind tunnel walls are found to change the circulation around the body in the wind tunnel. This effect is further accentuated if we either change the incidence or change the relative proximity of the wind tunnel walls.     

Virtual wind tunnel: An alternative approach for the analysis of bridge behaviour under wind effects

The study of bridge responses under wind-induced loads is based upon full aeroelastic model testing or hybrid methods which use section model tests and subsequent computer analysis. Both methodologies present several strong points and some shortcomings, specially related with the visualization of the bridge dynamic behaviour. Nowadays, advances and improvements in computational power and computer aided design technologies make possible a new way towards the feasible design of long span bridges considering its aerodynamic and aeroelastic behaviour. The virtual wind tunnel (VWT) technique developed by the authors joins together accurate section model testing with computer aided design in order to obtain a detailed computer visualization of the complete bridge behaviour under wind flow. The results obtained for the Tacoma Narrows Bridge and the Messina Strait Bridge are presented.     

基于虚拟检测技术的隧道交通参数检测方法研究

针对隧道监控中的交通参数检测问题，提出了一种基于虚拟检测技术的隧道参数检测方法，挖掘隧道几何模型，定义虚拟线圈和虚拟检测线，根据虚拟线圈感应变化，检测隧道中的车流量；通过拟合投影关系，检测车速，实验结果表明：该方法具有较高检测概率，满足系统的实时要求，并且具有很高的抗噪声干扰能力。     

Numerical study of the injection process in a transonic wind tunnel: The numerical details

Numerical prediction of an injection process was successfully performed. The physical problem corresponds to the mixing of a number of parallel supersonic jets with a subsonic main stream, in the presence of solid walls. In practice, this arrangement is to be used as a boosting device in a transonic wind tunnel, with the ultimate objective of extending the tunnel’s envelope without penalizing the main compressor. Five supersonic nozzles are installed at the floor and five at the ceiling of the transition module’s entrance section. Due to the great difference between cross-sectional typical lengths of nozzles and tunnel, the numerical tool has to have a three-dimensional capability. The core of the code is an adaptation of the finite-difference diagonal algorithm, and turbulence effects are properly tackled by the use of the Spalart and Allmaras one-equation scheme. Some simplifications were adopted in order to render the problem minimally tractable, especially in this initial numerical simulation stage, which is the reporting objective of this article. Albeit this, and due to the magnitude of the problem in hand, these simplifying initiatives were not sufficient to bring the calculations down to a scale of reasonable computer costs. Hence, a sequence of grids, coupled with a division of the computational domain, was adopted. Boundary conditions were thoroughly worked, especially the ones related to the domain of calculation’s entrance plane. This plane is important because of the many viscous gradient regions that project against it. Among the many settings under which a tunnel can operate there is one defined as the “design condition”, or else as the “design point”, as it is sometimes called. For a tunnel equipped with an injection system, the design point asks (besides many other specifications) for equal static pressures at the section where the supersonic jet meets for the first time the main stream coming from the tunnel circuit. We have simulated five different operating settings of the tunnel and among them the design condition. Therefore, we have results for the design as well as for many off-design points. The idea was to simulate the many tunnel settings and also to test the code’s ability to handle all these different situations. The code was duly validated and verified, and in the sequel the steady flow field in the mixing region was calculated. Many interesting and very important results were obtained, among which we would point out the existence of compression and expansion domes at the supersonic regions, the calculation of the many engineering parameters related to the injection process, and especially the determination of the injection’s gain threshold.     

Convergence to unconfined flow of the three-dimensional transonic self-correcting wind tunnel

The mixed difference method (ref. [1]) is used to investigate the convergence problem of the three-dimensional transonic self-correcting wind tunnel. The interior wind tunnel and the exterior unconfined flow-fields are described by the transonic small disturbance equation. In order to determine whether the unconfined-flow is obtained in the interior tunnel, two flow variables at a control surface are needed. They are the perturbation velocity components parallel to the free stream and perpendicular to the control surface. Their distributions are evaluated at the control surface for both the interior and exterior regions. The results of the numerical calculations indicate that after several iterations of one flow variable at the control surface the interior wind tunnel flowfield converges to the free-air flowfield.     

Pressure regulation inside a hypersonic wind tunnel using H-infinity optimization control

Hypersonic wind tunnel is a ground-based facility used to study the aerodynamic properties of space vehicles during re-entry. This paper aims at designing an H-infinity controller with krill herd optimization algorithm to regulate pressure inside the settling chamber of a hypersonic wind tunnel. The krill herd algorithm is a novel stochastic algorithm for improving the performance characteristics by optimizing the H-infinity controller parameters. The proposed algorithm minimizes the H-infinity norms by tuning the controller weighing function parameters. The dynamic characteristics of the settling chamber pressure with H-infinity and H-infinity control based on krill herd algorithm is studied by numerical simulations. The proposed algorithm is highly efficient and robust in controlling the settling chamber pressure in terms of performance parameters.     

一种基于组件的风洞通用测控平台设计

为了提高风洞测控系统及其软件的可扩展性和重用性,缩短软件开发周期,从风洞测控系统的特性与需求出发,综述了风洞测控软件通用化的现状,并基于面向对象思想和系统架构设计理念,提出了组件化风洞测控软件平台的层次结构,分析了用户定制层和功能实现层的组件划分、组件通信模式/接口和组件封装,讨论了基于组件的风洞测控平台原型系统设计,为风洞测控系统软件的进一步通用化提供了一种思路和方法。     

Complex automation of aerodynamic experiment in T-106 transonic wind tunnel

The system of complex automation of aerodynamic experiment in T-106 TsAGI transonic wind tunnel is presented. Data acquisition processes, as well as control processes for the model’s Mach number and angle of attack are automated on the basis of new data acquisition and control system involving IVK M2 data acquisition software package and VMIC control software package. The results of balance and pressure experiments (and of the combined ones) are presented. Stages of experimental results processing are described.     

Measuring and computational system of TsAGI T-128 transonic wind tunnel

Having been developed at TsAGI, measuring and computational system of T-128 transonic wind tunnel is presented. Structure of the system, as well as basic characteristics of the subsystems used for measuring the aerodynamic loads, pressure distribution and flow parameters are described. Specific features of the system’s software for the given wind tunnel are discussed. Application of the system enables to improve the accuracy of evaluating the aerodynamic characteristics of aircraft models by ten times.     

低速增压风洞风扇段温度监控系统研究

介绍了在低速增压风洞安全连锁系统中对风扇段轴承进行温度监控的监控系统。它是针对低速增压风洞内部的高压力、高雷诺数、多连锁节点的特点,基于单总线建立的温度监控系统。此监控系统由6只温度传感器组成,采用单总线方式,通过温度采集仪并入风洞安全连锁系统中,在满足监控精度的同时避免了多传感器带来的系统布线,有效地满足了风洞对高压力密封性多节点同时监控的要求,并保障了风扇段轴承温度监控数据的可靠性。     

基于CompactRIO的风洞喷管执行器位置监测系统开发

针对大型超声速风洞喷管设备,采用Compact RIO模块化仪器架构和LabVIEW开发平台,通过传感器、数据采集卡及上/下位机软件实现了对喷管执行器位置数据的采集、状态显示、分析、存储和预警等功能。利用该系统对2米超声速风洞喷管执行器进行监测分析,实验表明,该系统能实时显示喷管型面工作状态,及时判断故障产生的位置和超限情况,满足了执行器位置监测的实际需求,为操作者提供了有效的监测工具,提高了风洞喷管运行的安全性和可靠性。     

基于MSP430F5529的简易风洞控制系统设计

基于MSP430F5529设计了一个简易风洞控制系统。选用超声波传感器检测乒乓球在简易风洞中的位置,微控制器MSP430F5529通过对乒乓球当前位置的分析判断控制直流电机的转速,从而完成对乒乓球升降高度的实时控制。     

基于DSP的杆式风洞天平实时动态补偿系统

杆式应变天平是一种六维力传感器,在风洞试验中测量飞行器模型所受的各个方向的力和力矩。但是,其动态响应超调量大,调节时间长,无法满足动态测试的要求。选用数字信号处理器(DSP)TMS320F2812,研制了一种实时动态补偿系统,实现对应变天平六路输出信号的动态补偿,加快应变天平的动态响应速度。     

Numerical study of the injection process in a transonic wind tunnel. Part II: The off-design points

For many years now, injection has been of great utility in the wind tunnel activity. Sometimes injection is the sole source of power. Other times it is used in an auxiliary fashion in conjunction with the main compressor. This paper focuses on this last instance. In a transonic facility, some supersonic injectors are installed at the entrance of the transition section, with the ultimate aim of expanding the Reynolds number envelope without demanding extra power of the main compressor. The objective of this work is the numerical investigation of the mixing process between the supersonic streams coming out of the injectors, and the tunnel main subsonic current. In a first part of this reporting, the present authors have advanced the basic information, and discussed the results for the physical situation that was designated as “the design point”. This corresponds to a setting such that, exactly at the entrance of the mixing section — where the two flows start to interact —, the static pressures of the two mixing streams are equal. To obtain such state, one acts upon the stagnation pressure of the supersonic nozzles. The design point corresponds to a working condition, for which, in principle, losses are minimized. The aim of the present paper is to report upon a set of conditions that we refer to as the “off-design points”; here, the initial static pressures of the two currents are not equal. Besides investigating these new settings, many comparisons with the operation at the design point are also performed. Initially, an overview of the flow field for all cases is presented, and attention is called to the expansion and compression domes, that now, for the off-design points, are much more illustrative. After that, a thorough study is undertaken comprising the mixing layers growth behavior, and the performance of the mixing chamber in terms of pressure losses, overall gain and efficiency. As a consequence of these analyses, the nozzles stagnation pressure for a zero gain was obtained. This is an important result, because it represents the threshold for the efficient use of the injection process.     

The virtual magistrate

If mere ever was a glimmer of hope for me utopian paperless law office, it has long since vanished. Gone are the notions of unlimited online access to court dockets, filing of briefs over the Internet, and fully stocked cyber law libraries. In their place has come the Virtual Magistrate Project, a joint venture of the Cyberspace Institute, the American Arbitration Association, the National Center for Automated Information Research, and the Villanova Center for Information Law and Policy. The Virtual Magistrate is the first rapid-response, online dispute resolution system designed to arbitrate on issues of online messages and postings.     

Numerical model of a turbulent flow behind a heated grid in a wind tunnel

A closure of the Corrsin equation is performed using the gradient hypothesis connecting a third-order mixed correlation moment with a second-order two-point correlation function of a passive scalar field. A numerical model of the locally isotropic turbulence is constructed based on the closed system of the Kolmogorov and Yaglom equations. On the assumption of constant Loitsiansky and Corrsin invariants, a self-similar solution of the Corrsin equation is constructed corresponding to infinitely large Reynolds and Peclet numbers. A numerical model of the turbulence dynamics and temperature fluctuations behind a heated grid in a wind tunnel is constructed based on the closed Karman-Howarth and Corrsin equations.