Wind Tunnel System Research Articles

Magnetic Suspension and Balance System for High-Subsonic Wind Tunnel

A magnetic suspension and balance system (MSBS) was successfully developed for suspending a model against a high-subsonic flow. In the high-subsonic regime, the aerodynamic loads acting on the model increase with increasing flow speed and the fluctuation forces increase accordingly. The pitch/yaw directional instability of the model increases in the high-subsonic regime. To solve these problems, the power of the amplifiers and the controlling frequency of an MSBS for a 10 cm low-speed wind tunnel were increased to improve the control system response. A magnetic field was also introduced to compensate for the directional instability of the model by increasing the output of the front drag coil and decreasing that of the rear drag coil. This modification of the magnetic field enabled an ogive-cylinder model with a diameter of 10 mm and a length of 156 mm to be suspended in the MSBS up to a Mach number of 0.6.

Gust Alleviation Control using Prior Gust Information: Wind Tunnel Test Results

Abstract This paper reports dynamic wind tunnel test results of gust alleviation using preview control. The wind tunnel tests are conducted as a part of validation of gust alleviation control using an onboard Doppler LIDAR (Light Detection and Ranging) system, which was developed by JAXA (Japan Aerospace Exploration Agency) and can measure wind velocities in front of an aircraft. The wind tunnel system is composed of a gust wind generator, a half-span rigid aircraft model, a model support system and a digital controller unit. The aircraft model is allowed to move pitch direction by the support system. It is equipped with two control surfaces, which are controlled by commands from the controller unit. Since the LIDAR system cannot be used in the wind tunnel system, the LIDAR information is emulated using the predetermined timeseries of the gust wind generator and used for the preview control law. The wind tunnel tests are conducted with 1-cosine shape gust generation commands and the proposed preview control law is compared with a conventional feedback control law. The results show that the proposed control law is effective in alleviating vertical load caused by gust wind.

Assessment of the chemical-physical variables affecting the evaporation of organic compounds from aqueous solutions in a sampling wind tunnel

The aim of this work is the evaluation and the analysis of the different chemical-physical variables that affect the emission of volatile organic compounds (VOC) and odours from passive liquid area sources inside a wind tunnel, which is typically used for emission sampling. Three different compounds (acetone, butanol and ethanol), having different volatilization properties (e.g., boiling point, solubility), were studied in solution with water at different concentrations. The following physical parameters affecting the VOC volatilization in the Wind Tunnel system were evaluated: the velocity of the air flowing through the device, in a range from 0.01 to about 0.05 m/s, and the temperature of both the liquid source and the sweep air flow, in a range from 12 °C to 42 °C. The experimental results were compared with the existing volatilization models available in literature. In most cases the proposed theoretical model predicts well the experimentally measured concentration. Some discrepancies were observed for lower velocities and also by moving from the room temperature (20 °C); and those were discussed by making some considerations about the volatilization phenomenon. Moreover, the study clearly shows that it is not the gas phase temperature that controls the emission, but the temperature of the liquid phase, due to the effect of the latter on the vapour pressure of the compound, which is the main driving force of the phenomenon.

Development of air exchanging system for subsonic wind tunnel

The study analyzes main ways of air flow cooling in closed-circuit wind tunnels (subsonic and transonic): subject to air exchange (continuous partial exhaust of warm air and its change for colder outside air) and by means of the use of liquid-coolant stationery heat exchanger. It is shown that additional equipment is not required when applying air exchange to cool the flow and, in general, it can reduce costs of wind tunnel maintenance and, consequently, test prices. Based on an example of subsonic wind tunnel designed in TsAGI the evaluation of gas-dynamic and thermo-dynamic circuit flow properties are evaluated. The study also proposes options of air exchange arrangement for high-power operations at w=160 ms-1 in closed test section provided that the outside air temperature is Tf=20 °C. The paper represents the results of numerical simulation for air flow in the segments of wind tunnel duct in presence of air exchange holes.

Design of an experimental wind tunnel system for control applications

In this study, a low-cost experimental wind tunnel system for evaluation of control algorithms and utilization in teaching activities is presented. The system is designed inspired from conventional wind tunnels and has a basic design and low cost as can be realized in every laboratory. The design of mechanical part and electronics hardware and development of computer software are described in detail. The objective of the control system is to ensure the rotation speed of fan, which is placed at the end of the pipe, and track a desired trajectory by controlling air pressure in the pipe. Experimental results are also presented to demonstrate the performance of the system.

Theoretical and testing investigation of wind–rain coupling loads on some typical bluff bodies

The article presents a mathematical theoretical framework and fitting parameters with aspects of joint probability distribution of wind and rain, separate wind and rain action, and coupled wind and rain effects on steady and unsteady forces acting on some typical bluff bodies. Gumbel and copula functions were first selected to describe the joint probability distribution of wind speed and rain intensity. Then, two models, a raindrop impact model and an equivalent air density model, were adopted to quantify the loading action considering only separate wind and rain action, and simplified coupled effects with superimposition of wind and rain show that it would be accurate enough to neglect separated rain influence in steady wind and rain loading conditions. Furthermore, wind tunnel testing has been carried out under coupled wind and rain conditions with the help of a high-precision raining simulation system in TJ-1 wind tunnel on various reduced-scale models with some typical cross sections, such as circular and rectangular, thin plate, and streamlined box, and their aerodynamic loading and wind–rain-induced performance have been systematically compared. It has thus been found that the coupling effects of wind and rain should not be neglected in steady and unsteady force models.

Odor impact assessment of trace sulfur compounds from working faces of landfills in Beijing, China

Odor pollution from landfills is causing a growing number of public complaints and concerns. Compared with hydrogen sulfide (H2S) and ammonia (NH3), odor impacts of trace sulfur compounds (TSCs) are arousing concerns due to their low odor threshold values (OTVs). Working face on landfill sites has been claimed as major source of odor impacts. This study estimated the odor impacts of fugitive TSCs from the working face of a large typical municipal solid waste (MSW) landfill in Beijing, China. A modified wind tunnel system was introduced to estimate emission rates of TSCs, which is a basic requirement for odor impact assessment. The odor activity value (OAV) method was introduced for odor evaluation. Fieldwork in the selected landfill was conducted from 2014 to 2015. Methyl mercaptan (CH3SH), dimethyl sulfide, dimethyl disulfide (DMDS), and carbon disulfide (CS2) were the TSCs studied in this work. The spatial concentration distributions of the TSCs were calculated on the basis of the Gaussian dispersion model in a “normal case” scenario and a “worst case” scenario. DMDS showed the highest emission rate (7.18 μg m−2 s−1), and CH3SH was the dominant odorous compound with an average emission rate of 4.58 μg m−2 s−1. The dispersion modeling indicated that the odor impact distances of the TSCs in the studied landfill for the normal case and worst case scenarios were 495 ± 96 m and 9230 m at the downwind regions, respectively. Results of this study can benefit the formulation of strategies for odor control and abatement in landfill sites.

Wind tunnel measurements of forced convective heat loss from multi-megawatt cavities of solar central receiver systems

We investigated the forced convective heat loss from a model of a multi-megawatt cavity receiver of a concentrated solar power (CSP) tower system in a high-pressure wind tunnel. Measurements of 5 geometrical configurations of this model as well as measurement uncertainties are reported in this contribution. The experiment covered a Reynolds number range of between 2·106 and 8·106, based on the external dimensions and flow field. In general, the measured values are highly sensitive to the geometrical configuration, the wind velocity, and the wind direction. The results show that the maximum forced convective heat loss for all configurations occurs when the wind blows from frontal directions of between 60° and 80° relative to the tower symmetry plane. We found that the peak location does not vary for different inclinations, but does vary for different aperture openings. Also, the results show that the direction of the wind causes the forced convective heat loss to vary with a factor of up to 6.1, but at least with a factor of 2.6. Last but not least, our power-law correlation of the dependency of the forced convective heat loss on the Reynolds number matches literature values.

Investigation of mass transfer phenomena affecting emission rate of gaseous compounds from porous solids

Abstract The main objective of this study is to investigate the mass transfer phenomena affecting the emission of acetone from a porous solid. In order to simulate this type of emission in a laboratory-scale and in a repeatable way it was decided to set up a system consisting of a dry solid layer with an underlying wet layer. This type of investigation aims to give a scientific basis for the understanding of the factors affecting emission rates when sampling solid area sources with a wind tunnel system. This in turn is important in order to make results obtained with different devices somehow comparable. The study was carried out by following a modellistic and an experimental approach, and then comparing the results. The comparison of experimental and modelled results shows a good agreement, proving that the developed model is able to describe the phenomenon, thereby taking into account the phenomenon intra-solid gas diffusion, as well as capillary rise of the liquid. As a final result, the proposed model is capable to describe properly how the emission rate from a porous solid is affected by the sweeping airflow velocity, which was the final purpose of this study. Although the developed model is valid for the simplified experimental set-up studied (consisting of a dry solid layer with an underlying wet layer and involving the use of pure acetone), the understanding of the phenomena affecting mass transfer in this simplified situation can be transferred to the investigation of diffusion of other compound through more complex solids.

삼중음속 풍동 가변노즐 자동 운영시스템 개발

삼중음속 풍동 가변노즐 자동 운영시스템 개발

Active Vibration Control of the Sting Used in Wind Tunnel: Comparison of Three Control Algorithms

In wind tunnel tests, cantilever stings are often used as model‐mount in order to reduce flow interference on experimental data. In this case, however, large‐amplitude vibration and low‐frequency vibration are easily produced on the system, which indicates the potential hazards of gaining inaccurate data and even damaging the structure. This paper details three algorithms, respectively, Classical PD Algorithm, Artificial Neural Network PID (NNPID), and Linear Quadratic Regulator (LQR) Optimal Control Algorithm, which can realize active vibration control of sting used in wind tunnel. The hardware platform of the first‐order vibration damping system based on piezoelectric structure is set up and the real‐time control software is designed to verify the feasibility and practicability of the algorithms. While the PD algorithm is the most common method in engineering, the results show that all the algorithms can achieve the purpose of over 80% reduction, and the last two algorithms perform even better. Besides, self‐tuning is realized in NNPID, and with the help of the Observer/Kalman Filter Identification (OKID), LQR optimal control algorithm can make the control effort as small as possible. The paper proves the superiority of NNPID and LQR algorithms and can be an available reference for vibration control of wind tunnel system.

On the aerodynamic characteristics of stay cables attached with helical wires

To investigate the aerodynamic characteristics of stay cables attached with helical wires, a series of wind tunnel tests and computational fluid dynamics simulations were both carried out on the smooth and helical-wire cable models. The diameters of helical wires include 2, 3, and 4 mm, and the distances between adjacent helical wires include 200, 300, and 600 mm. Pressure taps were uniformly arranged on seven cross sections of the cable models. First, wind tunnel tests including 50 test cases were conducted to measure the wind forces and wind pressures on the cables using the forced vibration system in HD-2 wind tunnel. The effects of the helical wires on the mean and fluctuating aerodynamic forces and the correlation coefficients along the cable axis were investigated in detail based on the experimental data. Second, large Eddy simulation module incorporated in software FLUENT® was used to simulate the aerodynamic forces on the smooth and helical-wire cables. The parameters of the cable and the helical wire are similar to those used in the wind tunnel tests. The results show that helical wires can attenuate vortex shedding and reduce the wind pressure correlation along the cable axis. Within the Reynolds number range from 0.4 × 105 to 1.6 × 105, the mean drag force of the helical-wire cable is lower than the value of the smooth cable, and the correlation coefficient decreases with the increase in wind velocity. The results obtained from wind tunnel tests and computational fluid dynamics simulations agree well with each other. Furthermore, the wind velocity contour around the helical-wire cables obtained from computational fluid dynamics simulations visually indicates that the approaching flow is forced to separate at the surface of the helical wire in advance, which makes the vortex shedding disorder along the cable axis.

A Nonlinear Block-oriented Model for Wind tunnel System

This paper develops a novel nonlinear block-oriented model for the wind tunnel system. Based on the available signals, the wind tunnel system can be divided into three parts, namely, the exhaust valve loop, the choke finger loop and the flow field. Then the considered plant is described as a nonlinear block-oriented model. The exhaust valve subsystem and the flow field subsystem are both expressed by linear dynamic models, whereas the choke finger subsystem exhibits a nonlinear characteristics and is approximated by a pseudo-Hammerstein model. Based on the above parameterization model, the recursive identification algorithms are presented for three subsystems. Interestingly, the adaptive weighted recursive least squares algorithm is applied to the pseudo-Hammerstein model, and the hierarchical recursive least squares algorithm is used to reduce the computational complexities. Both simulations and experiments are carried out to verify the effectiveness of the proposed method.DOI: http://dx.doi.org/10.5755/j01.itc.46.3.14457

Sustained release of H2S from a microsphere system encapsulated with NaHS to promote cell proliferation and angiogenesis for wound healing in diabetic mice

The main objective of this study is to investigate the mass transfer phenomena affecting the emission of acetone from a porous solid. In order to simulate this type of emission in a laboratory-scale and in a repeatable way it was decided to set up a system consisting of a dry solid layer with an underlying wet layer. This type of investigation aims to give a scientific basis for the understanding of the factors affecting emission rates when sampling solid area sources with a wind tunnel system. This in turn is important in order to make results obtained with different devices somehow comparable. The study was carried out by following a modellistic and an experimental approach, and then comparing the results. The comparison of experimental and modelled results shows a good agreement, proving that the developed model is able to describe the phenomenon, thereby taking into account the phenomenon intra-solid gas diffusion, as well as capillary rise of the liquid. As a final result, the proposed model is capable to describe properly how the emission rate from a porous solid is affected by the sweeping airflow velocity, which was the final purpose of this study. Although the developed model is valid for the simplified experimental set-up studied (consisting of a dry solid layer with an underlying wet layer and involving the use of pure acetone), the understanding of the phenomena affecting mass transfer in this simplified situation can be transferred to the investigation of diffusion of other compound through more complex solids.

Operating safety of a hot-shot wind tunnel with combined test gas heating in stabilization mode

In the present paper, we analyze emergency situations typical of short-duration wind tunnels with electric-arc or combined test-gas heating in the presence of stabilization and diaphragm-rupturing systems, which occur in the case of no discharge initiation in the settling chamber, with the capacitor battery having remained charged during the start of wind-tunnel systems. For avoiding such emergency situations, some additional changes based on using feedback elements are introduced into the wind-tunnel design: the piston of the fast-response valve is made hollow for increasing the volume of the shutoff cavity and for making the release of pressure from this cavity unnecessary; the high-pressure channel, which connects the piston and the piston rod with the settling-chamber cavity, is filled with a liquid and is closed from the side of the settling chamber with a piston; the device for controlled diaphragm breakdown is provided with an external electric circuit intended to control the diaphragm-rupturing process. Those modifications allow subsequent functioning of the wind-tunnel systems only in the presence of heat-supply-induced pressure growth in the settling chamber of the wind tunnel.

New horizons of vehicle aerodynamics

Vehicle aerodynamics and wind tunnel technology are progressing towards more realistic simulations of the real-world on-road environment. This paper presents an overview of the new systems which were implemented during the recent wind tunnel upgrade at Forschungsinstitut für Kraftfahrwesenund Fahrzeugmotoren Stuttgart as well as comparable computational fluid dynamics simulations. The fully interchangeable road simulation system features an interchangeable five-belt system and three-belt system in the same full-scale automotive wind tunnel. This system offers the efficiency of a five-belt system combined with the more sophisticated ground simulation technique of a wide belt system, which is necessary to assess the aerodynamic properties of sports cars and racing cars. In order to simulate on-road wind conditions, a side-wind generator can be installed to generate a turbulent flow field in the wind tunnel test section. It could be shown that the commonly determined drag coefficient at 0° yaw angle in the smooth flow environment of today’s wind tunnels is not representative of the drag found in real on-road wind conditions. Additionally, the investigations in unsteady side-wind conditions indicate that the commonly used approach to determine the side-wind sensitivity of a vehicle underestimates the forces occurring in turbulent flow conditions. A validated simulation model is presented. The simulation results are in good agreement with the experimental results and can be used as a complementary tool when assessing the unsteady aerodynamic behaviour of a vehicle; this behaviour can be coupled to a vehicle dynamics model for virtual road testing in the Stuttgart full-motion driving simulator. The unsteady-behaviour effects can be evaluated comprehensively, and the results allow a subjective assessment of the unsteady response of the vehicle. Furthermore, the aeroacoustic wind noise in on-road wind conditions is investigated during the development of the vehicle. The side-wind generator reproduces the natural stochastic cross-wind and allows the effect of these wind conditions to be investigated in the aeroacoustic wind tunnel. The results show similar ratings to those in on-road tests when compared with subjective listening tests. In summary, the techniques introduced open up new horizons in the field of vehicle aerodynamics and aeroacoustics, which are a step closer towards real-world conditions in automotive engineering.

Review of the published exposure data to pesticides for residents and bystanders, and for environmental risk assessment: Final report

Review of the published exposure data to pesticides for residents and bystanders, and for environmental risk assessment: Final report

Sweating-boosted air cooling using nanoscale CuO wick structures

Low heat transfer coefficient (HTC) in air/fin-side is the bottleneck of dry cooling strategies for thermal power plants. Inspired by the phase change heat transfer during the perspiration of mammals, a sweating-boosted air cooling strategy with on-demand water dripping is proposed. The testing samples are featured with macroscale grooves for global liquid delivery, and with nanoscale hydrophilic copper oxide (CuO) wick structures for local liquid spreading. The experiments of sweating-boosted air cooling are conducted in a wind tunnel system. There are three wetting conditions with increasing dripping rates: dry, partially wetted, and flooded conditions. In the partially wetted conditions, the surface temperatures reduce and HTCs increase with increasing dripping rates. For a given dripping rate of water, HTCs are enhanced and surface temperatures are reduced with increasing air velocities. High air velocity and low surface temperature have a trade-off effect on the evaporation process. This effect results in almost constant saturated dripping rates for a given thermal load. A linear relationship between the saturated dripping rates and the thermal loads confirms that the evaporation dominates the heat transfer process of sweating-boosted air cooling. Complete surface wetting is obtained on the designed surfaces, but no obvious effect of groove width on HTCs is observed. Sweating-boosted air cooling can significantly increase air-fin side HTC in air cooled condenser (ACC), and dramatically reduce the water consumption compared to current water evaporative condenser (WEC). This research provides a fundamental understanding on the sweating-boosted effects on the air cooling.

Pressure Measurements on Yacht Sails: Development of a New System For Wind Tunnel and Full Scale Testing

The paper presents an overview of a joint project including Politecnico di Milano, CSEM and North Sails, aiming at developing a new sail pressure measurement system based on MEMS sensors (an excellent compromise between size, performance, costs and operational conditions) and pressure strips and pads technology. These devices were designed and produced to give differential measurement between the leeward and windward side of the sails. The research has been developed for the final employment on the Lecco Innovation Hub Sailing Yacht Lab, a 10 m length sailing dynamometer which aims at being the reference contemporary full scale measurement device in the sailing yacht engineering research field, to enhance the insight of sail steady and unsteady aerodynamics. The pressure system is described in details, the data acquisition process and system metrological validation are reported; furthermore, some results obtained during a wind tunnel campaign carried out at Politecnico di Milano Wind Tunnel, as a benchmark of the whole measuring system for future full scale application, are reported and discussed in details. Moreover, the system configuration for full scale testing, which is being finalized at the time of this paper, is also described

Flashover characteristics of cylindrical insulator in high-speed sand environment

With the launching of Lanzhou-Xinjiang high-speed railway in Northwest China, high-speed train running in sand environment will cause strong high-speed airflow with sand around it, which seriously threats the long-term service performance of roof insulators. To study the flashover characteristics of insulator under the condition, a small size wind tunnel system is established to simulate high-speed sand environment, the influence of airflow speed, sand particle size and sand flux on the flashover voltage of cylindrical insulator is investigated. Results show that, in pure high-speed airflow environment, the flashover voltage of insulator has an increase-decrease variation trend with the increase of airflow speed. The flashover mechanism is due to the combined effects of airflow blowing effect and airflow density. In sand environment, flashover voltage will decrease obviously which is caused by nonuniformity of electric field, but the decreasing degree will become small with the increase of airflow speed. Sand particle size and sand flux have negative influence on flashover voltage of insulator. These research results can provide theoretical basis for service performance of roof insulators in high-speed sand environment.