Wind tunnel tests on train scale models to investigate the effect of infrastructure scenario

The cross wind risk analysis is today, within the European railway operators, one of the most important items related to the safety problem. In order to define the risk associated with the cross wind along a railway line, the effect of the infrastructure scenario on the aerodynamic loads acting on a vehicle have to be investigated. A typical railway line is mainly characterized by two main types of scenario: viaduct and embankment. In this work, the aerodynamic coefficients of the ETR500 train, measured through wind tunnel tests, for the standard TSI infrastructure scenarios (flat ground with and without ballast and rail and 6 m-high embankment) and for a typical Italian viaduct are presented. Moreover, each infrastructure is characterized in terms of flow modification with and without train. A comparison between the experimental results obtained with the different scenarios allows to point out the effects of the infrastructure on the aerodynamic loads.     

Wind tunnel tests on a savonius rotor

Tests have been made in a wind tunnel on a number of Savonius rotor configurations in wind speeds of 6–9 m/s. The variables tested were blade aspect ratio, blade overlap and gap and the effects of adding end extensions, end plates and shielding.For low aspect ratios (～1) with no additions the efficiency was low (～0.065) but for higher aspect ratios (～5) with optimum blade configuration and shielding a maximum value of efficiency of 0.25 was obtained. Tests with three and four bladed configurations gave appreciably lower values of efficiency.A special study was made of wind tunnel corrections for blockage ratios up to 0.3.     

大跨度铁路站房屋盖结构风洞试验与等效静风荷载研究

以哈尔滨西客站站房屋盖结构为研究对象,采用刚性模型同步测压风洞试验对建筑表面的平均及脉动风荷载进行测定,结合本征正交分解技术对风压场进行重构及预测,解决了风压测点与结构有限元模型节点的不匹配问题。分别建立整体结构和屋盖结构有限元模型,利用时程分析方法考察了下部结构对风致响应的影响,研究表明下部结构会导致屋盖结构的刚度弱化,建模中忽略下部结构可能导致对屋盖结构位移和内力响应的低估。引入多目标等效静风荷载分析方法,以结构在风荷载作用下的最大动力响应为控制指标获得针对多个等效目标的静风荷载分布,并对等效结果进行了验证,结果表明该方法可以实现以少量静风荷载分布形式实现所有响应均与动力极值响应等效。     

Wind tunnel tests on model crane structures

Empirical methods for calculating wind forces on latticed tower-like structures at any angle to the wind and that had been developed earlier by the authors, are here extended to the calculation of wind forces on crane jibs. Wind-tunnel tests on model latticed and telescopic crane jibs and the model of a complete mobile crane are described. The patterns of forces and moments on the two types of jib are compared and tentative methods of calculation proposed. Higher lift forces were found with the telescopic than with the latticed jib and the overturning moment resulting from wind action on a mobile crane was found to be due almost entirely to the jib.     

Wind tunnel tests on a 3m diameter Musgrove windmill

A 3m diameter model of a two bladed Musgrove vertical axis windmill has been tested in the British Aerospace wind tunnel at Filton. Tunnel constraints were kept to a minimum by using a low flow blockage and appropriate corrections were applied to the measurements.

The results of these tests demonstrate the good performance of this type of windmill. Comparison of the measured performance with predictions from a simple mathematical model show excellent agreement.

Maximum loads measured on the windmill are not well predicted by the mathematical model. In order to reconcile measurement and prediction large induced crossflows must be postulated at some blade rotational positions.     

紊流积分尺度对典型桥梁断面静力#br# 系数影响规律的风洞试验研究

为研究紊流积分尺度对典型桥梁断面静力系数影响的规律,文章通过在风洞中模拟紊流对典型桥梁断面进行测力试验。借助尖塔,格栅等方式模拟紊流的传统试验方法,难以模拟实际风场中的大紊流积分尺度。文章采用自主研制的主动控制翼栅,有效增大试验中风场的紊流积分尺度,通过控制主动控制翼栅的振动频率产生不同紊流积分尺度的风场。对单箱梁、双箱梁、桁架梁、边主梁、边箱梁五种典型桥梁断面在紊流下和均匀流下的静力系数进行了测定,其中紊流由主动控制翼栅产生。将五种典型桥梁断面在紊流下的静力系数和均匀流下的静力系数进行对比分析,结果表明在大紊流积分尺度下,阻力系数随紊流积分尺度增大而增大,且小于均匀流下的阻力系数值。结果也表明,在均匀流来测定桥梁断面静力系数对于实际工程应用是偏于安全的考虑,因此建议进行节段模型测力试验时,在均匀流中进行。     

Wind tunnel tests on compartment fires with crossflow ventilation

When a fire occurs in a room at ground level or a compartment located in the higher floors of a very tall building , the strong ambient wind will play an important role in fire spreading and smoke movement behavior. However, wind effect on compartment fire in cross ventilation condition has not been fully studied so far. In the present study, an effort has been made to study the wind effect on compartment fire in cross ventilation condition through experimental investigations. The experimental fire was generated by 250 ml n-heptane on the floor center of a cube enclosure with two opposite vents on the walls. The inside and outside gas temperature profiles at different vertical and horizontal locations were recorded by two thermocouple matrixes. The ambient wind velocity was set to 0, 1.5 and 3 m s⁻¹. It is observed that the ambient wind would enhance the fire severity by increasing the compartment fire temperature and reducing the time to flashover. The spilled-out flame/plume would extend horizontally farther with the increase of wind speed. Simple theoretical analysis shows that there is a critical wind velocity, or a dimensional number, to differentiate whether the gas flow across the vents is bidirectional or unidirectional, which is believed to influence enclosure fire behavior greatly.     

Model scale tunnel tests with water spray

A model scale study (1:23) was carried out in order to improve the basic understanding of water spray systems in longitudinal tunnel flow. The water spray system consisted of commercially available axial-flow hollow cone nozzles. Tests with both a deluge system made of 12 nozzles placed directly above the fire source and a water curtain system consisting of four nozzles placed either downstream or upstream of the fire source were carried out. A wood crib was used to simulate the fire source, which was designed to correspond to a HGV (heavy goods vehicle) fire load in large scale. A second wood crib was used as a target pile and was placed downstream the ignited wood crib. The parameters varied were the water flow rate and water pressure, the longitudinal ventilation rate and the arrangement of the nozzle system. Possible fire spread between wood cribs, with a free distance corresponding to 15 m in large scale, was investigated.     

大跨车站隧道施工技术探讨

就改建铁路襄渝线安康至重庆增建二线新月河隧道出口车站段隧道施工,探讨了大跨隧道施工采用中壁法、三台阶法隧道施工方法的特点,为以后同类隧道施工提供借鉴。     

Wind tunnel simulation on re-circulation of air-cooled condensers of a power plant

The criteria as well as the methods and measurements of wind tunnel simulation on wind effects on air-cooled condensers in a power plant were discussed. The parameter of re-circulation was suggested to describe the wind effects on the efficiency of the condenser. The result of practical project models shows that great wind effects of both wind speed and the angle of the incident flow on the efficiency of the condenser. It is recommended that in the initial stage of a new or an extension power plant, which is equipped with an air-cooled system, the wind tunnel simulation is necessary and helpful. Combined with the local wind climate data, a more reasonable, economic and safety schematic design of a power plant could be achieved.     

球面壳体表面风压分布特性风洞试验研究

球面壳体是工程中一种常用的屋面结构形式。本文通过刚性模型风洞试验,对不同场地类别下球面壳体表面风压分布进行了同步测量。根据测到的同步风压分布数据,对壳体表面风压场特性进行了分析,包括平均风压系数及脉动风压系数分布、脉动风压的自功率谱及互功率谱分布、风压场的本征正交分解特性、雷诺数对壳体表面风压分布的影响等。结果表明,球面壳体模型表面风压分布受雷诺数的影响明显,且模型的曲面特性使得由风场本征正交分解得到的前几阶特征模态对整个风压分布的贡献增大。该研究为这类结构在抗风分析中风荷载的确定及数值模拟提供试验依据。     

Model scale tunnel fire tests with automatic sprinkler

The study focuses on the performance of an automatic sprinkler system in a model scale tunnel with longitudinal ventilation. A total of 28 tests were carried out in a 1:15 model scale tunnel using an automatic sprinkler system with glass bulbs. The maximum heat release rate, energy content and failure of the automatic sprinkler system were analysed. The results show that high ventilation rates and low water flow rates result in a failure of the automatic sprinkler system in a longitudinal ventilated tunnel fire. The main reason for the failure under the tested water flow rates was the effect of the longitudinal flow on the fire development and the hot gas flow close to the sprinklers. The fire development and the activation heat release rate of the first activated bulb are intimately related to the ventilation velocity. The fire spread to the neighbouring wood crib was investigated and a presentation of tests conducted using a deluge system are given.     

Model scale tunnel fire tests with longitudinal ventilation

Results from a series of tests in a model tunnel (1:23) are presented. Tests were carried out with longitudinal ventilation under different fire conditions. Wood cribs were used to simulate the fire source, which was designed to correspond to a scaled-down HGV (Heavy Goods Vehicle) fire load. The parameters tested were: the number of wood cribs, type of wood cribs, the longitudinal ventilation rate and the ceiling height. The heat release rate, fire growth rate, maximum gas temperature beneath the ceiling, temperature distribution, total heat flux at floor level, flame length, and back-layering length were investigated. Correlations for these parameters were investigated and proposed for longitudinal flow in tunnels.     

Wind tunnel tests for mean wind loads on partially clad structures

Many structures, such as buildings under construction, industrial process structures, and manufacturing and storage facilities, are temporarily or permanently partially clad. Scant wind load data for these structures are available in the literature and wind codes. An investigation was undertaken at the L.S.U. Wind Tunnel Laboratory to study the aerodynamic behavior of these structures. Mean force coefficients for various cladding arrangements are reported for models of a 10-storey structure for two plan aspect ratios (1:1 and 3:1) in smooth, grid turbulent, and boundary layer flow. Three flow regimes were tested to validate results against published data and to investigate the possibility of reducing the number of key variables. Results for the fully clad and unclad cases compared well with available data for ground-mounted prisms and lattice frames, respectively. It was found that force coefficients for some of the cladding configurations significantly exceeded those for a fully clad structure of the same overall geometry. Additionally, the manner in which the force coefficients varied with wind direction was found to differ dramatically from the fully clad cases for some of the cladding arrangements. The conditioning of the approach flow was found to be less important for unclad models than for partially or fully clad configurations.     

Wind tunnel tests of effects of atmospheric stability on turbulent flow over a three-dimensional hill

This paper presents a wind tunnel study on the turbulent structure of the airflow around a three-dimensional hill model placed in a boundary-layer flow. The effect of atmospheric stability: stable, neutral and unstable on the flow field of the boundary layer is examined. The wind velocity is measured with a three-dimensional laser doppler anemometer (LDA). Measurements analysis includes mean velocity, turbulent velocity, Reynolds stress and turbulence energy profiles around the hill. The main results are as follows: (1) The mean wind velocity does not vary with the stability at the hilltop; it reaches a maximum at the back of the hill, for the unstable case. (2) The turbulent velocity at the back of the hill reaches its peak value at the height of the hilltop. It takes maximum value for the stable boundary layer flow, and become smaller for the neutral flow and the unstable flow. Buoyancy production has little effect on the turbulence energy. (3) A clear peak of /U_H² is observed at a height near Z/H=1. The peak value becomes the largest for the stable case and the smallest for the unstable case.     

Measurement of smoke in large scale fire tests

Large scale fire tests involving actual products and prototypes are of major importance in that they enable the interactions of various materials, prototypes and design features to be evaluated. The fire regime can be selected to reproduce the anticipated end-use hazard.This paper discusses the various approaches used to measure smoke in large scale fire tests, and their requirement and their limitations, as well as correlations between full scale test rigs.     

Wind forces on and excitation of a 130-m concrete chimney

A field experiment concerned with wind forces on a large concrete chimney and the vibrations caused by these forces is presented.Some preliminary results concerning the consistency of the measurements are discussed, and some conclusions regarding chimney vibrations are given.A method for on-line dynamic calibration of wind pressure transducers is presented. The method has worked satisfactorily, but improvements concerning zero-pressure biases are needed.A universal mean-pressure distribution for the Stigsnaes chimney is presented. An estimated drag coefficient of 0.64 (independent of height above the ground) seems reasonable for transcritical Reynolds numbers.The roughness parameter of the sea for on-shore wind directions is found to be of the order of centimetres. A slight indication of increasing roughness with increasing wind speed is observed.     

Wind tunnel tests and manoeuvre simulator tests with different types of sails and ships

The present paper describes how wind tunnel tests combined with manoeuvring simulator tests and wind statistics can be used to estimate the mean reduction in power consumption for larger ships equipped with sail systems for auxiliary propulsion purposes. The results presented is based on wind tunnel tests with a 60, 000 tdw bulk carrier carried out for the Burmeister & Wain Ship Design in Denmark.     

全站仪大比例尺数字化地形测量精度研究

以吕梁市煤炭工业学校校内地形测量为例,通过全站仪与CASS7.0成图软件的综合应用,阐释了数字化地形测图的主要原理及步骤,包括测区概况、图根控制测量、碎步采集和CASS7.0成图,最后提出了提高数字化测图精度的有效措施。