Comparison and optimization design methodology for open-loop subsonic wind tunnel

The Low-Speed Anechoic Wind Tunnel at Sun Yat-Sen University is a premier facility designed for experimental research on aerodynamics and aeroacoustics of aircraft scaled models or components. As a 3/4 closed-circuit wind tunnel with a contraction section nozzle dimension of 0.8 m × 0.6 m, it can be configured either as a closed test section or an open-jet section. The freestream velocity in the closed test section can be adjusted from 5 m/s to 80 m/s, while the openjet section ranges from 10 m/s to 70 m/s. The test section is enclosed within an anechoic chamber with dimensions of 5.5 m × 6 m × 3.5 m to ensure non-reflecting conditions. After the wind tunnel’s construction, comprehensive tests were conducted to evaluate its acoustical and aerodynamic performance. This paper presents the design criteria and characterization of the wind tunnel’s key components, along with the methods and results of benchmarking the flow quality and acoustic performance. This wind tunnel features exceptional flow quality with low turbulence intensity of 0.08% , 1% in the closed test section and open-jet section, respectively. The minimal level of background noise can attain a decibel level of 6.9 dBA under no-flow conditions, and at maximum flow velocity (70 m/s ) in the open-jet test section, the background noise reached 74.9 dB(A).The findings demonstrate that the aerodynamic and aeroacoustic performance indicators of the wind tunnel are comparable to similar facilities worldwide, positioning it as the leading aeroacoustic research facility in the Guangdong-Hong Kong-Macao Greater Bay Area at present.

Informasi kecepatan angin merupakan salah satu parameter yang diperlukan BMKG yang diukur dengan menggunakan anemometer. Oleh karena itu diperlukan kalibrasi terhadap anemometer agar menghasilkan data kecepatan angin yang tepat dan akurat dengan menggunakan wind tunnel. Wind tunnel atau terowongan angin adalah suatu alat untuk melakukan studi dan penelitian mengenai interaksi antara gerakan udara dengan benda-benda yang ada didalam aliran udara. Wind Tunnel dalam kalibrasi perlatan meterorologi adalah alat kalibrator untuk kecepatan angin yang dapat menghasilkan angin laminar yang kecepatannya dapat dikontrol sehingga dapat digunakan untuk kalibrasi sensor kecepatan angin. Penelitian ini dilakukan untuk perancangan prototipe wind tunnel, dimana profil kecepatan angin diukur untuk mengetahui intensitas turbulensi dengan mengendalikan kecepatan motor kipas pada wind tunnel. Perancangan prototipe ini bertujuan untuk menunjang kegiatan belajar praktek kalibrasi peralatan meteorologi di STMKG agar taruna/i mengetahui proses kalibrasi anemometer menggunakan wind tunnel. Wind tunnel hasil rancangan dan implementasi memiliki panjang total 150 cm dengan intensitas tubulensi antara 3.11 % sampai 6.55 %. Anemometer Casella dengan nilai koreksi 0.05 m/s setelah proses kalibrasi digunakan sebagai standar dalam melakukan proses kalibrasi.

This paper proposes a process of determining geometrical configurations to simulating the flow in designing sub-sonic open circuit wind tunnels. Design rules that are based on empirical results and Computational Fluid Dynamics (CFD) model are integrated as a Low-Speed Wind Tunnel Design Tool. The tool allows users to undertake the automatic calculation through wind tunnel designed requirements to detailed flow fields analysis. Three configurations with the overall length of 7 to 10 meters and width from 3.5 to 4.2 meters are suggested. The design wind tunnels have the test section (cross section) of 1.7 × 1.7 meters squared and the test section velocity of 15 meters per second. The simulation results help to choose the best-designed wind tunnel configuration for manufacturing in the future.

The effects of unsteady wind on the performances of a newly developed cross-axis wind turbine: A wind tunnel study

In this paper, low-speed smoke wind tunnel has been designed and fabricated for the insects’ flow field visualization. The test section and the contraction section of the tunnel are optimized and determined as to size by the method of computational fluid dynamics. And fairing devices are equipped in different sections to reduce the turbulence intensity and increase the flow uniformity in the experimental sections. For the smoke visualization of small insects, the smokeemitting equipment has been specially designed and carefully debugged. Composed of wind tunnel, light source and high-speed camera, experimental platform for visualization and filming of insect flight flow field has been established. B esides, the feasible and stable method for insect fixing has been designed. With the smoke wind tunnel, flow filed visualization experiment for the honeybee’s flapping was conducted and smoke flow filed in the experiment was recorded and analyzed. Near-filed and far-filed vortex structure when the honeybee fly can be recorded clearly. The expe rimental results indicate that the experimental platform is appropriate for flow filed study on insects flapping. Keyw ords: wind tunnel; honeybee; smoke lines; flow field

This paper presents the design and manufacturing of open circuit low-speed wind tunnel. The design of the contraction cone, test section and diffuser are finalized by the numerical analysis performed on ANSYS CFD software. A unique insight into the design of the contraction cone is presented. A fifth-order polynomial is used to model the contraction cone in PRO-E software. It allowed designing the test section with minimum turbulence and flow serration and a flow velocity profile of 20 m/s. The cross-sectional area of the test section and diffuser are selected after analytical calculations. The diffuser is designed as such to avoid pressure loss by incorporation changes in the rectangular cross-section. The initial study performed on the design helped us to select the fan with suitable power. Moreover, the intake of the contraction cone is equipped with the honeycomb structure of facilitating the laminar flow into the contraction cone. Following on to the initial numerical analysis, the fabrication of the wind tunnel is performed. Besides, a separate lift/drag measuring force system is also prepared; the intuitive design is cost-effective as well as accurate. The placement of anemometer helped us to directly measure the test section velocity, which is found to be 17 m/s.

During recent years, wind energy has moved from an emerging technology to a nearly competitive technology. This fact, coupled with an increasing global focus on environmental concern and a political desire of a certain level of diversification in the energy supply, ensures wind energy an important role in the future electricity market. For this challenge to be met in a cost-efficient way, a substantial part of new wind turbine installations is foreseen to be erected in big onshore or offshore wind farms. This fact makes the production, loading and reliability of turbines operating under such conditions of particular interest.

The characterization of a new wind tunnel at the University of Florida’s Research and Engineering Education Facility is presented. The tunnel is specifically designed to operate in the low Reynolds number regime in which Micro Air Vehicles operate. The wind tunnel is driven by a 60 inch, 50 hp axial blower controlled by a variable frequency drive. The tunnel entrance consists of a flow conditioning section and a 8:1 area contraction ratio that results in a 42” square entrance to the open jet test section. The enclosure surrounding the test section has a volume of nearly 2000 ft with an axial length of 10 ft. The free stream velocities in the tunnel range from nominally 0 to 22 m/s by altering the frequency on the variable frequency drive. Flow uniformity studies for free stream velocities of 2 and 15 m/s were conducted demonstrating a potential core throughout the test section of at least 60% of the 1.14 m contraction exit. Experiments using hot wire anemometry were also performed and the turbulence intensities were found to be less 0.22% for free stream velocities greater than 1m/s.

In order to evaluate the accuracy of computational fluid dynamics (CFD) for flow over a ship geometry, a comparison with an existing wind tunnel test of a simplified LHA hull with wind straight down the bow is made. One of the U.S. Navy's main interests in ship airwakes is the effect they have on aircraft operating nearby. In the interest of providing a more uniform flowfield in the vicinity of the ship, the wind tunnel test also investigates the effect of adding a downward -deflected flap to the bow, meant to mimic the rounded deck edge at the bow of later LHD -class ships, in contr ast to the sharp 90 -degree corner found on LHA - and earlier LHD -class ships. The CFD portion of this test also evaluates the effectiveness of the bow flap to show if CFD can match the trends of such geometry modifications. Furthermore, the CFD test investi gates the sensitivity of the solution to the grid resolution at the bow, where a large separation bubble affects a large portion of the flight deck, and will also determine if filtering the CFD data to mimic the performance of the wind tunnel equipment alt ers the results. This study seeks to validate CFD against wind tunnel data for this geometry and reinforce the wind tunnel assessment of the bow flap’s effectiveness. I. Introduction All branches of the U.S. military share an interest in the operation of air craft in the vicinity of ships. The airwake shed as wind flows over a ship can greatly influence the safety and ease of such operation. Features such as antennae, masts, radomes, deck equipment, and superstructures generate a complex flowfield that varies substantially with wind speed and direction. Due to the expense of repeating flight tests over different combinations of wind speed and direction, and with different aircraft types, CFD becomes an important tool in reducing such a test matrix by screening test conditions to those most crucial, and by evaluating ship geometries to predict problems and establish best design practices early in a ship's planning stage. To date, wind tunnels have borne much of the load for ship airwake testing, but they suffer f rom several drawbacks. Obviously, wind tunnels must use very small scale factors for ships, but they cannot achieve the airspeed required to match full -scale Reynolds numbers (Re). The small scale also decreases the period and size of pertinent flow featur es, making them difficult to detect. In addition, wind tunnel tests often require lengthy surveys or prior knowledge of the flowfield to find and adequately resolve off -body flow phenomena. In contrast, CFD can run any arbitrary physical scale, output resu lts at a user -determined frequency, and provide results over the entire solution space as a matter of course. However, wind tunnels certainly still provide an invaluable service in validating CFD and in testing conditions for which CFD is currently not sui table.

This paper presents the design and construction of a small-scale low-speed open circuit wind tunnel suitable for experimental testing and analysis of aerodynamic phenomena. The wind tunnel is specifically designed for low-speed applications, focusing on flows within velocities of 35 meters per second with turbulence conditions below 10 percent. The design process of a wind tunnel involves considerations such as dimensions, design parameters, and instrumentation to ensure accurate flow measurements, with key components including a settling chamber, contraction section, test section, diffuser, and drive system working together to remove disturbances, create uniform flow, minimize blockage effects, and generate required airflow for accurate aerodynamic testing. This paper highlights the design considerations, key components, construction techniques, and the significance of the wind tunnel for aerodynamic testing, validation of simulations, and education. The designed wind tunnel is capable of producing controlled and repeatable low-speed flow conditions, making it suitable for a wide range of applications, including aerodynamic testing of scaled- down models, validation of Computational Fluid Dynamics (CFD) simulations, and educational purposes. The small-scale design allows for cost-effective construction and operation while maintaining reliable results.

The aim of this project was to develop a wind tunnel that enables the study of human performance during various types of sports and physical activities by examining the influence of aerodynamic drag, precipitation, frictional forces and gravitational forces on uphill and downhill travel on a moving substrate. An overall design for a wind tunnel and working section containing a large treadmill was drafted, followed by computational fluid dynamics simulations of flow conditions to assess the design’s feasibility and select from different geometries prior to its construction. The flow conditions in the completed wind tunnel were validated using different flows, speeds and treadmill inclinations. Pilot experiments were carried out using a cross-country skier to investigate the effect of aerodynamic drag on oxygen uptake during double poling and the maximal achieved speed when rolling on a declined treadmill. The purpose was to validate the usefulness of the tunnel. The results showed that flow conditions are acceptable for experiments even in worst-case scenarios with maximal inclined and declined treadmill. Results also showed that aerodynamic drag has a significant impact on the skier’s energy expenditure.

The paper considers the details of design and construction of a small-sized wind tunnel with an open circuit and a closed test section for investigating the blades of horizontal-axis wind turbines. The effect of different types of jet straighteners on the turbulence of the flow in the test section has been studied. Turbulence flow distributions Tu at Reynolds numbers Re from 5·103 to 2·104 are obtained using Laser Doppler Anemometry methods. As a result, the wind tunnel design with average flow turbulence of 1.6 % is obtained. The flow visualization of NACA 64-618 airfoil at Re = 5·103 is obtained.

Airflow and concentration characterisation and ammonia mass transfer modelling in wind tunnel studies

Until recently, airfoil design has largely been a process of trial and error that has relied heavily upon the intuition and experience of the designer. Using an experimental database for airfoils, a designer would normally employ an educated guess to make modifications to the design. He would then build a new model and test it in the wind tunnel. After several of these design iterations, an airfoil with the desired characteristics would be obtained. Now, with the development of advanced Computational Fluid Dynamics (CFD) codes, much of the trial and error process in aerodynamic design can be eliminated. A CFD code models air flow around a given geometry by numerically solving the governing equations of fluid dynamics on the computer. Rather than testing a new model in the wind tunnel at each design iteration, it is much faster and cheaper to test new airfoil designs with CFD calculations. However each new design requires many (several hundred) computationally intensive CFD calculations before an acceptable design evolves using an optimization procedure. This process is called direct design optimization. In order to alleviate the problems associated with the computationally intensive nature of the direct design methods, attempts have been made to calculate the shape of an airfoil that would have a specified flow distribution over its surface. This is essentially the inverse of a direct CFD calculation in which the shape of the airfoil is given and the flow is calculated; hence it is referred to as inverse design. Summaries of previous work in inverse design are given by Jameson [1], Cabuk and Modi [2], Lewis, Peters and Agarwal, [3] and Agarwal and Lewis [4], and Lewis [5]. In this paper, the inverse design has been formulated as a variational problem in which a control system minimizes the differences between the actual and the desired velocity (or pressure distributions) over the airfoil surface by making successive changes to the shape of the airfoil. A flow chart of the design method is shown in Fig. 1. First, an initial airfoil and the desired velocity (or pressure distribution) are input. The Mach number and angle of attack are also specified. Then a flow solver (Full Potential or Euler) computes the actual velocity and pressure distribution around the airfoil. Next, a cost functional, which represents the deviation of the actual velocity (or pressure distribution) from the desired velocity (or pressure distribution) is computed. If the cost functional has reached a minimum, then the process terminates. Otherwise, a variation is made to the shape of the airfoil such that the cost functional is reduced. The process is repeated so that the cost functional is minimized thereby minimizing the deviation between the actual and the desired velocity (or pressure distributions). The inverse design enhances the efficiency of the aerodynamic design process by several orders of magnitude. Several test cases are shown to demonstrate the method and its robust characteristics (accuracy, stability and efficiency) for aerodynamic design.

The dust storm on the surface of Mars is a severe threat to Mars exploration missions. Taking adequate measures to avoid the impact of the harsh wind-blown dust environment is indispensable. Ground simulation of the Martian high-speed windblown dust environment is helpful for analysis of the environmental effects and evaluations of the suitability of the components and materials. In this paper, a novel reflux subsonic low-density dust wind tunnel is presented to simulate the high-speed windblown dust environment of the Martian atmosphere with a velocity of more than 100 m/s. The sand and dust are fed into the wind tunnel through the ejector assembly together with the compressed gas, resulting in high uniformity of particles in the test section. The construction design of the Mars wind tunnel is introduced. The key parameters, which are the nozzle parameters and the contraction curve, are discussed in detail. The convergent nozzle is most suitable for the ejector assembly. Moreover, the bicubic curve is selected as the contraction curve. The gas-particle two-phase computational fluid dynamic (CFD) simulations demonstrate the rationality of the wind tunnel design.