Design Of Wind Tunnel Research Articles

Numerical investigation of air flow in a supersonic wind tunnel

In the framework of TsAGI’s supersonic wind tunnel modernization program aimed at improving flow quality and extending the range of test regimes it was required to design and numerically validate a new test section and a set of shaped nozzles: two flat nozzles with flow Mach number at nozzle exit M=4 and M=5 and two axisymmetric nozzles with M=5 and M=6. Geometric configuration of the nozzles, the test section (an Eiffel chamber) and the diffuser was chosen according to the results of preliminary calculations of two-dimensional air flow in the wind tunnel circuit. The most important part of the work are three-dimensional flow simulation results obtained using ANSYS Fluent software. The following flow properties were investigated: Mach number, total and static pressure, total and static temperature and turbulent viscosity ratio distribution, heat flux density at wind tunnel walls (for high-temperature flow regimes). It is demonstrated that flow perturbations emerging from the junction of the nozzle with the test section and spreading down the test section behind the boundaries of characteristic rhomb’s reverse wedge are nearly impossible to eliminate. Therefore, in order to perform tests under most uniform flow conditions, the model’s center of rotation and optical window axis should be placed as close to the center of the characteristic rhomb as possible. The obtained results became part of scientific and technical basis of supersonic wind tunnel design process and were applied to a generalized class of similar wind tunnels.

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.

Preliminary design of a supercritical CO2 wind tunnel

The preliminary design of a test-rig for non-ideal compressible-fluid flows of carbon dioxide is presented. The test-rig is conceived to investigate supersonic flows that are relevant to the study of non-ideal compressible-fluid flows in the close proximity of the critical point and of the liquid-vapor saturation curve, to the investigation of drop nucleation in compressors operating with supercritical carbon dioxide and and to the study of flow conditions similar to those encountered in turbines for Organic Rankine Cycle applications. Three different configurations are presented and examined: a batch-operating test-rig, a closed-loop Brayton cycle and a closed-loop Rankine cycle. The latter is preferred for its versatility and for economic reasons. A preliminary design of the main components is reported, including the heat exchangers, the chiller, the pumps and the test section.

Wind induced vibrations of a high tapered obelisk: wind tunnel tests, numerical analysis and design of countermeasures

The structure studied in this paper is a 85 meters high tapered obelisk, made of reinforced concrete for the first 9 meters and of steel welded plates for the upper 76 meters. Its bluff cross section consists of two closely spaced triangular sections that are scaled linearly with the height from ground. Having a complex bluff section and being a light structure, aerodynamic instabilities and vortex induced vibrations were investigated using a mixed experimental-numerical approach, in order to define wind loads for the structural design, and possible interventions aimed at mitigating the dynamic effects due to wind action. Exploiting the regular tapering of the obelisk section, a rigid sectional model with constant section was initially tested in wind tunnel: static aerodynamic coefficients and vortex-induced response as a function of the Scruton number were measured for several angles of attack. The experimental sectional results were successively used to assess numerically the response of the structure considering tapering, the gradient of wind speed, the modal shapes, and the correlation of wind actions. Even though the numerical analysis showed that the tapering drastically reduces aerodynamic issues, the achieved results underlined the pressing need to increase the damping of the structure in order to avoid galloping and vortex induced vibrations for wind speeds within the design range; to this aim tuned mass dampers were designed.

Development of Wind Tunnel for Ultrafine Palm Oil Fuel Ash Separator

Palm Oil Fuel Ash (POFA) is a pozzolanic material that has great potential in concrete production. POFA sizes range from 1 to 10 μm is preferable. Thus, there is a need for efficient method to separate the POFA according to the sizes needed. This study explores the idea of using a simple wind tunnel as a separator for ultrafine POFA. The existing operation of the wind tunnel is simulated using ANSYS-CFX, a numerical modelling software. The identified weakness of the wind tunnel design is located at the hopper. The wind tunnel is simulated with a different air inlet velocity in order to visualize the air flow profile as well as air flow energy at the hopper. Different air inlet velocities has a similar air flow profile but the air flow intensity is different. For further study the modifications of the air flow profile were conducted. By altering the hopper angle shows that the air flow profile is changed. Based on the simulation results, the hopper at 60° yields the best flow characteristic. At angle 60° of the hopper, the air flow is mostly directed downward into the tunnel and the air flow energy is low. Therefore, it allows the POFA to be directed into the tunnel and reduced the ultrafine POFA losses at the tip of the hopper. This practical method utilizes a simple open wind tunnel that enables the process to be more efficient and cost efficient thus the production of ultrafine POFA can be increased.

Expansion of capabilities of the short-duration wind tunnel with an opposing pressure multiplier

A method for raising the maximum settling-chamber pressure in a short-duration wind tunnel equipped with pressure multipliers arranged in opposition to each other for stabilization of test gas parameters is proposed. For this purpose, a wind-tunnel design with an additional third pressure multiplier attached to the body of the second pressure multiplier was developed. The rod of the additional multiplier contacts the large-area piston stage of the second multiplier, and the pre-piston space being connected to the receiver. The inclusion of an additional pressure multiplier in the wind-tunnel design at the maximum attainable driver-gas pressure of 150−170 bar, defined by the standard industrial pressure of air used for filling wind-tunnel receivers with the driver gas, allows a two-fold increase in the maximum settling-chamber pressure, from 1100 to 2000−2200 bar. For raising the maximum settling-chamber pressure above 2000–2200 bar, the use of one additional pressure multiplier proved to be insufficient because, in the latter case, its becomes necessary to simultaneously raise the driver-gas pressure over 150−170 bar.

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 1m in height and 1m in width, and the maximum wind velocity in the test section can be up to 80m/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.

고고도 장기체공 태양광 무인기 EAV-3의 프로펠러 설계 및 성능해석

고고도 장기체공 태양광 무인기 EAV-3의 프로펠러를 설계하고 전산해석을 수행하였다. 실험설계법(Design of Experiment, DOE)을 사용하여 설계변수들의 실험점들을 획득하고 목적함수와 구속함수들에 대한 크리깅 근사모델을 생성하였다. 요구조건 및 제약조건들과 함께 반응면을 평가하여 프로펠러 형상을 설계하였으며, 근사모델 기반의 최적설계를 수행하여 설계의 타당성을 검증하였다. 상용 CFD 코드를 이용하여 해석을 수행하고 그 결과를 설계코드 및 시험결과와 비교하였다. 설계점 고도에서 해석 결과가 설계코드의 예측과 잘 일치하였다. 또한 시험장치와 지지대 기둥에 의한 폐쇄효과가 풍동시험 결과에 포함되어 있으며, 이를 포함한 해석 결과가 시험 결과와 잘 일치함을 확인하였다. Design and performance analysis of propeller for solar-powered HALE UAV, EAV-3 are conducted. Experiment points of design variables are obtained by using Design of Experiment(DOE) and Kriging meta-model is generated for objective and constraints function. The geometry of propeller is designed by evaluating the response surface with requirement and restrictions. The validity of the design is verified by meta-model based optimization. Computational analyses are carried out by using commercial CFD code and the results are compared with those from a design code and wind tunnel test. The results showed good agreement with predictions of the design code at the design altitude. Also, it is confirmed that the blockage effect due to the measurement device and support strut is included in the test data and the results including this effect compare well with the test data.

Simulation study on modeling for design parameters analysis of free-piston tunnels

A dynamic model was designed and developed using thermodynamic mass conservation equation, energy conservation equation, flow equation of nozzle and motion equation for moving piston and design parameter analysis of free-piston tunnels was proposed. The proposed model was validated by comparing the predictions made with the dynamic model established with the experimental data reported in some of the references and used to run simulation. Simulation results indicated that the target pressure and temperature could be quickly obtained by selecting and adjusting design parameters with the proposed model while the pressure and temperature output of the reservoir were kept long stable with a pneumatic hydraulic driving device. The time domain conditions of free-piston wind tunnel could be established through numerical study at different gas source pressure. The pressure and temperature of reservoir could be obtained by adjusting the valve opening of gas source. The variable specific heat ratio has a remarkable effect on the performance of free-piston wind tunnel. For the variable specific heat ratio, the temperature and pressure of reservoir was lower than the constant specific heat ratio. It was therefore concluded that the proposed model was suitable for performing the design parameter analysis of free-piston wind tunnels, and so, it could be used to facilitate the design of free-piston wind tunnels for long working at high Mach number.

THE DEVELOPMENT OF A MULTI-PURPOSE WIND TUNNEL

This manuscript contains the development stages of a multi-purpose wind tunnel built at the Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia. The fully automated wind tunnel is named Pangkor after an island in Perak, Malaysia. The development of the wind tunnel consists of three stages namely the design, fabrication and testing & commissioning. The computational fluids dynamic (CFD) approach was employed to ascertain the main geometries to optimize space utilization. Calculations are made based on typical wind tunnel design guidelines. Pitot tubes-pressure transducer, hotwire anemometry, temperature, room humidity and barometric sensors were used to verify actual flow of our construction. A traverse installed at the wind tunnel is capable of a two dimensional movements. The 15 kW axial fan used is especially selected because of space limitation. A variable frequency drive (VFD) connected to fan’s motor allows velocity control from a computer. All devices are connected a computer with one single controlling software; Scilab – ensuring ease of operation. The project shows that, with a limited budget, a wind tunnel with full functionalities could be constructed

Optimization of a subsonic wind tunnel nozzle with low contraction ratio via ball-spine inverse design method

The goal of wind tunnel design is to generate a uniform air flow with minimum turbulence intensity and low flow angle. The nozzle is the main component of wind tunnels to create a uniform flow with minimal turbulence. Pressure distribution along nozzle walls directly affects the boundary layer thickness, pressure losses and non-uniformity of flow velocity through the test section. Although reduction of flow turbulences and non-uniformity through the test section can be carried out by nozzles with high contraction ratio, it increases the construction cost of the wind tunnel. For decreasing the construction cost of nozzle with constant test section size and mass flow rate, the contraction ratio and length of nozzle should be decreased; that causes the non-uniformity of outlet velocity to increase. In this study, first, three types of nozzle are numerically investigated to compare their performance. Then, Sargison nozzle with contraction ratio of 12.25 and length of 7 m is scaled down to decrease its weight and construction cost. Having scaled and changed to a nozzle with contraction ratio of 9 and length of 5 m, its numerical solution reveals that the non-uniformity of outlet velocity increases by 21%. By using the Ballspine inverse design method, the pressure distribution of the original Sargison nozzle is first scaled and set as the target pressure of the scaled down nozzle and geometry correction is done. Having reached the target nozzle, numerical solution of flow inside the optimized nozzle shows that the non-uniformity just increases by 5% in comparison with the original Sargison nozzle.

Design and Testing of ISU-AABL Wind and Gust Tunnel

A wind tunnel with advanced capabilities will aid research efforts to understand the complex fluid structure interaction problems encountered in aerospace engineering, industrial aerodynamics and wind engineering applications since wind tunnels remain an integral component of the design process for wind sensitive structures. Whether dealing with the aerodynamics of aerospace, mechanical or civil engineering structures many issues remain to be fully resolved-including the role of non-stationary gust interactions, Reynolds number effects, and the significance of small-scale turbulence. Building the next generation of such wind tunnels will contribute to the understanding of these issues. A combination Aerodynamic/Atmospheric Boundary Layer (AABL) Wind and Gust Tunnel with a unique active gust generation capability has been developed for various applications at Iowa State University (ISU). This wind tunnel is primarily a closed-circuit tunnel that can be also operated in open-return mode. It is designed to accommodate two test sections (2.44m x 1.83m and 2.44m x 2.21m) with a maximum wind speed capability of 53 m/s. This paper describes the wind tunnel and its components and presents a comparison of the predicted and measured design parameters. It shows that the wind tunnel is capable of generating uniform flow with very low turbulence in the aerodynamic test section and produces gust magnitudes around 27% of the mean flow speed.

Full-Scale Turbine Vane Endwall Film-Cooling Effectiveness Distribution Using Pressure-Sensitive Paint Technique

Researchers in gas turbine field take great interest in the cooling performance on the first-stage vane because of the complex flow characteristics and intensive heat load that comes from the exit of the combustion chamber. A better understanding is needed on how the coolant flow interacts with the mainstream and the resulting cooling effect in the real engine especially for the first-stage vane. An authentic flow channel and condition should be achieved. In this study, three full-scale turbine vanes are used to construct an annular-sector cascade. The film-cooling design is attained through numerous layback fan-shaped and cylindrical holes dispersed on the vane and both endwalls. With the three-dimensional vane geometry and corresponding wind tunnel design, the true flow field can thus be simulated as in the engine. This study targets the film-cooling effectiveness on the inner endwall (hub) of turbine vane. Tests are performed under the mainstream Reynolds number 350,000; the related inlet Mach number is 0.09; and the freestream turbulence intensity is 8%. Two variables, coolant-to-mainstream mass flow ratios (MFR = 2%, 3%, and 4%) and density ratios (DR = 1.0 and 1.5), are examined. Pressure-sensitive paint (PSP) technique is utilized to capture the detail contour of film-cooling effectiveness on the inner endwall and demonstrate the coolant trace. The presented results serve as a comparison basis for other sets of vanes with different cooling designs. The results are expected to strengthen the promise of PSP technique on evaluating the film-cooling performance of the engine geometries.

Design and Construction of an Open-circuit Wind Tunnel with Specific Measurement Equipment for Cycling

In order to overcome resistance a cyclist has to deliver a total power output of which 90% is necessary to overcome the aerodynamic drag [1,2]. In order to perform research in this aerodynamic drag a wind tunnel has been built by the Belgium company Flanders’ Bike Valley. This wind tunnel is designed using classical design rules and with specific cycling requirements an open-circuit wind tunnel is designed. This wind tunnel, containing a test section in which two cyclist can be positioned in succession, contains three main measurement systems to investigate the aerodynamic drag of a cyclist. A balance is used for the measurements of aerodynamic forces acting on the model, a bikefitting test is included to have a perfect fit between cyclist and bike and finally a PIV system is installed to investigate the flow behaviour.

Quantifying wind and pressure effects on trace gas fluxes across the soil–atmosphere interface

Abstract. Large uncertainties persist in estimates of soil–atmosphere exchange of important trace gases. One significant source of uncertainty is the combined effect of wind and pressure on these fluxes. Wind and pressure effects are mediated by surface topography: few surfaces are uniform and over scales of tenths of a metre to tens of metres, air pressure and wind speed at the ground surface may be very variable. In this paper we consider how such spatial variability in air pressure and wind speed affects fluxes of trace gases. We used a novel nested wind tunnel design comprising a toroidial wind tunnel, in which wind speed and pressure may be controlled, set within a larger, linear wind tunnel. The effects of both wind speed and pressure differentials on fluxes of CO2 and CH4 within three different ecosystems (forest, grassland, peat bog) were quantified. We find that trace gas fluxes are positively correlated with both wind speed and pressure differential near the surface boundary. We argue that wind speed is the better proxy for trace gas fluxes because of its stronger correlation and because wind speed is more easily measured and wind speed measurement methodology more easily standardized. Trace gas fluxes, whether into or out of the soil, increase with wind speed within the toroidal tunnel (+55 % flux per m s−1), while faster, localized surface winds that are external to the toroidal wind tunnel reduce trace gas fluxes (−13 % flux per m s−1). These results are consistent for both trace gases over all ecosystem soil types studied. Our findings support the need for a revised conceptualization of soil–atmosphere gas exchange. We propose a conceptual model of the soil profile that has a "mixed layer", with fluxes controlled by wind speed, wind duration, porosity, water table, and gas production and consumption.

Thermodynamics and Fluid Mechanics of a Closed Blade Cascade Wind Tunnel for Organic Vapors

The organic Rankine cycle (ORC) offers great potential for waste heat recovery and use of low-temperature sources for power generation. However, the ORC thermal efficiency is limited by the relatively low-temperature level, and it is, therefore, of major importance to design ORC components with high efficiencies and minimized losses. The use of organic fluids creates new challenges for turbine design, due to dense gas behavior and the low speed of sound. The design and performance predictions for steam and gas turbines have been initially based on measurements and numerical simulations of flow through two-dimensional cascades of blades. In case of ORC turbines and related fluids, such an approach requires the use of a specially designed closed cascade wind tunnel. In this contribution the design and process engineering of a continuous running wind tunnel for organic vapors is presented. The wind tunnel can be operated with heavy weight organic working fluids within a broad range of pressure and temperature levels. For this reason, the use of classical design rules for atmospheric wind tunnels is limited. The thermodynamic cycle process in the closed wind tunnel is modeled, and simulated by means of a professional power plant analysis tool, including a database for the ORC fluid properties under consideration. The wind tunnel is designed as a pressure vessel system and this leads to significant challenges particular for the employed wide angle diffuser, settling chamber, and nozzle. Detailed computational fluid dynamics (CFD) was performed in order to optimize the important wind tunnel sections.

Wind erosion prevention characteristics and key influencing factors of bryophytic soil crusts

Biological soil crusts (BSCs) are generally considered to reduce wind erosion, however, the extent of reductions is highly dependent on the vegetation type, soil moisture status, and their interactions in the field. The interrelationships between these factors or their combined effects are relatively unknown. The objectives of this study were to evaluate the contributions of the crust coverage (CC), associated with the soil moisture content (SMC), and the vegetation coverage (VC) to reduce wind-erosion and to provide a basis for the effective management of BSCs. We used an orthogonal design and large-scale wind tunnel simulations to determine the erosion-resistance characteristics of BSCs, and the effects of soil moisture content (SMC), vegetation coverage (VC) and crust coverage (CC) on its wind erosion reductions. Our results showed that 1) the medium SMC + low CC + high VC were the most effective contributors in decreasing the wind erosion modulus; 2) the high SMC + medium CC + low VC primarily reduced the sand-transport rate; 3) the medium SMC + high CC + low VC, with the smallest aeolian sand-flow structure index, resulted in the lowest level of aeolian sand-flow saturation; 4) the high SMC + high CC + medium VC exhibited the highest threshold wind velocity; and 5) the VC and CC were found to have significant effects on the surface roughness, but the SMC did not. BSCs should be strongly protected during dry and windy seasons in the spring and winter because of their value in reducing wind erosion. The BSC may be moderately disturbed during wet and weak wind seasons in the summer or autumn to ameliorate soil moisture conditions, especially in the sites with high vegetation coverage, without exacerbating wind erosion. Management that carefully considers the timing and disturbance of BSCs will help to determine the sustainable balance between the “protection” and “destruction” of BSCs and their effective use in reducing wind erosion.

Design and Development of Low-Cost Wind Tunnel for Educational Purpose

The presence of wind tunnel is undoubtedly bringing infinite possibilities to studying and understanding complex fluid flows. However, commercial wind tunnel is expensive and only limited to highly-focus researchers or exclusive institutions. This paper discusses the design and development of a low-cost, educational-purposed, open-typed subsonic wind tunnel. In this work, an open-typed subsonic wind tunnel is designed with the aim of achieving turbulent intensity (in the working section) below or equal to 5%, within the budget of RM 1500 and a working speed of 6 m/s – 8 m/s to meet the Reynolds number in the order of 105. The conceptual design was studied using Ansys Fluent 14.5 and the optimal design was then developed and experimentally verified.

A new wind tunnel for the study of pressure-induced separating and reattaching flows

AbstractThe design, construction, and validation of a new academic wind tunnel is described in detail. The wind tunnel is of a classical, blow-down type and generates a pressure-induced, turbulent separation bubble on a flat test surface by a combination of adverse and favorable pressure gradients. The Reynolds number, based on momentum thickness just upstream of separation, is Reθ≃ 5,000 at a free-stream velocity ofUref= 25ms−1. The length of the separation bubble is estimated at 0°42 ± 0°02m by three different methods. Results of a numerical simulation demonstrate the absence of flow separation in the wind-tunnel contraction. This results in a turbulence level of about 0·05% in the test section. Oil-film visualisation experiments show that the flow near the wall is strongly three-dimensional in the recirculating region and that the topology of the limiting streamlines is consistent with experiments performed on configurations with fixed separation. Finally, spatial variations of the forward-flow fraction have been documented using a thermal-tuft probe and are shown to compare well with the results of the oil-film visualisation.

Design of Mini Wind Tunnel Based on Coanda Effect

An experimental investigation and CFD treatment were employed to design mini-wind tunnel based on Coanda effect for model tests and basic research. The inlet source flow is efficiently creating smooth steady airflow with acceptable noise, achieving the possibility of placing the test target closer to the source of flow with reasonable estimates of turbulence intensity. The design aims at achieving flow uniformity in the working section midplane, preventing separation in the contraction and minimizing the boundary–layer thickness. Intensive measurements after construction demonstrate the significance of the design process and validate the CFD predictions. The results are represented in graphic form to indicate the aspects of the contraction ratio. The numerical and experimental results show the uniformity of velocity distribution inside the working section. Tracing of separation and backflow is crucial allowing a variety of realistic demonstrations to be performed. The numerical solution provides a powerful tool to demonstrate the rate of boundary–layer growth inside the working section and validate against the empirical correlations with insignificant wall–friction drag. Assessment study to address large–scale wind tunnel based on coanda effect would be considered.