Dimensioning, construction, and validation of an open-circuit wind tunnel for aerodynamic spray studies

In this study, the design of a wind tunnel was carried out to observe airflow through an airfoil, streamlines and turbine blades. To accommodate this, in this study a design was made of an open return wind tunnel. In this case, an open circuit wind tunnel type will be made because the construction is simpler and the manufacturing costs are relatively cheaper compared to the closed circuit wind tunnel type. The Wind Tunnel is designed with Open CLosed Wind Tunnel (OCWT) type. The OCWT is designed to consist of fan and housing, diffuser, test section, contraction, honeycomb. The OCWT design uses an operating fan to circulate air into the test section. The maximum air speed in the Test Section is 5 m/s with a flow that is closed to laminar. The recommended diffuser has a dimension of 50 cm on the side that is attached to the test section and 52 cm on the side facing the fan with an inclination angle of 1.79o. The driver uses a 16 inch exhaust fan with a power of 74 W to make the flow in the Test Section stable at a speed of 2 m/s.

Compact multi-fan wind tunnels are increasingly used for engineering and environmental studies where laboratory space is limited. However, achieving acceptable flow quality in such facilities remains challenging due to elevated turbulence intensity and velocity non-uniformity caused by fan–fan interactions and short flow-conditioning lengths. This study presents the design, construction, and experimental evaluation of an open-section compact multi-fan blower wind tunnel with an overall length of less than 8 m and a test section measuring 4.2 m × 2.8 m. Rather than applying a formal mathematical optimization algorithm, flow quality was improved through an iterative, engineering-driven refinement of key geometric and flow-conditioning elements. Successive design modifications—including bell-mouth intakes, fan caps, honeycomb structures, diffuser gratings, and settling chamber extension—were systematically implemented and experimentally assessed. Flow performance was quantified using spatially resolved measurements of mean velocity, turbulence intensity, velocity non-uniformity, skewness, and kurtosis over a defined effective core region. Experiments conducted at fan rotational speeds of 600, 1000, and 1200 rpm demonstrate consistent improvements in flow quality. The combined flow-conditioning strategy reduced the spatially averaged turbulence intensity by approximately 21%, 44%, and 47% at the respective speeds, while maintaining test-section velocities of up to 10 m s −1 . The final configuration achieved an average turbulence intensity of approximately 18%–20% together with improved velocity uniformity and statistically balanced turbulence. The results demonstrate that effective flow homogenization can be achieved in compact multi-fan wind tunnels without long settling chambers or contraction nozzles, making the proposed facility suitable for structural wind loading and environmental flow simulations under space and budget constraints.

The 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-driven, turbulent separation bubble on a flat test surface. The Reynolds number, based on momentum thickness just upstream of separation, is Reθ ' 5000 at a free-stream velocity of Uref = 25 m/s. The length of the separation bubble has been estimated at 0.42 ± 0.02 m by three different methods. Experimental and numerical results 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 visualization 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 visualization.

In the planning and design of a new wind tunnel the choice between closed and open-circuit types is a very important one. If on one hand the open –circuit solution is attractive for its low price and continuous fresh test air, on the other hand the test section flow quality is potentially affected by external winds. This sensitivity becomes especially critical at low-test speeds. Although many open-circuit wind tunnels have been built, there have been some problems either of low operating efficiency or sensitivity to external winds, or both. In this respect both ends of the tunnel are objects of concern. In the present paper, however, the authors concentrate their attention to the wind tunnel inlet section. At the Instituto Tecnologico de Aeronautica a non-return wind tunnel is currently under design. The test section flow quality requirements are very strict and the test-section turbulence level is to be as low as 0.05% of the mean flow kinetic energy. To insure that the desired turbulence level and flow uniformity at the test section is achieved the tunnel will have a 10:1 contraction, a honey comb and three screens with provision for an extra one. Further, the 35meter long facility has its inlet section, the contraction and the test section inside a 25x10 room. The diffuser, the fan section and the exit section are mounted outside the laboratory room. Figure 1 shows the tunnel layout. Although its position inside the laboratory is beneficial as does not expose the inlet section directly to the outside wind it also arises following concerns: (i) to operate the wind tunnel a large 6mx2.5m door will have to be open. Both side ends of this door will generate a shear layer exactly in front of the facility air intake (ii) the tunnel inlet section is not symmetrical in respect to the laboratory’s walls, being much closer to the one on its right-hand side. The 3.8m wide by 3.16 m high inlet is only about 20 cm away from both the floor and the ceiling of the room. In order to quantify these influences on the mean velocity distribution and on the turbulence level, at the tunnel air intake, an experimental study was made on a 1/10 scale model of the part of the tunnel to be built inside the lab.

Design and construction of an open loop subsonic high temperature wind tunnel for investigation of SCR dosing systems

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.

On the basis of the overall structure design and aerodynamic calculation of the annular low-speed wind tunnel, this paper uses the CFD numerical simulation technique to study the influence of the contraction curve form, the contraction ratio and the open/closed loop form of the test section on the flow field quality of the wind tunnel test section, and then gives the three-dimensional geometric model and the numerical simulation results. It is found that the best flow field quality can be obtained by using the bicubic curve, the contraction ratio of 10.24 and the closed loop form of the test section under the same fan condition. The three-dimensional modeling method is adopted in this paper, which can obtain more accurate numerical simulation result than the two-dimensional modeling method. Thus, the numerical simulation result provides a solid theoretical basis for the design and construction of the actual low-speed wind tunnel.

The present study aims to investigate the effect of the contraction profile on the flow quality such as the turbulent intensity, flow uniformity and pressure compared to baseline case (existing one). Primarily, losses of every wind tunnel part should be calculated. Hence, the total pressure losses of the whole wind tunnel circuit can be determined and all these losses are added up. This technique is required to evaluate the required power to operate the wind tunnel. As result, this method is well-suited with both of opened and closed-circuit wind tunnels. Moreover, two different profiles of the contraction are compared to the baseline wind tunnel (existing one) using the Computational Fluid Dynamics (CFD) as a basis for the comparison and analysis of the airflow properties through the whole wind tunnel design. The necessary parameters are the flow conditions within the test section that included the velocity, turbulent intensity and flow uniformity as well as the pressure distribution. The results showed that the turbulent intensity is decreased by 29.7 % with more uniform flow inside the optimized wind tunnel, when the “eye design contraction wall” is used. The contraction profile (wall design shape) plays an important role to effect on the flow quality inside the test section. Therefore, a special attention should be given when designing the wind tunnel with a specific contraction profile.

A multipurpose subsonic wind tunnel facility has been designed for the Korea Air Force Academy in South Korea, and construction of this facility is nearing completion. This wind tunnel will be used in development of aircraft and ground vehicles as well as for basic studies in aeronautical engineering. The facility includes the wind tunnel and a building complex with offices, workshops, and test hall. The main test section dimensions are 2.45 m high, 3.5 m wide and 8.7 m long. Velocity ranges from 5 to 92 m/s with a fan power of 2,000 kW. High flow quality is achieved, with turbulence intensity designed to be below 0.05%rms (u'/U) and 0.1%rms (v'/U, w'/U). How angularity is designed to be less than +.0.1 deg. The wind tunnel has interchangeable test sections, several model support systems, a variety of instrumentation systems, and a probe traverse system. The external balance can be elevated to provide high accuracy for the various model types and to accommodate model/test section exchanges. The test facility systems and the building are integrated to provide excellent model handling and testing productivity. *Cheong-Ju, South Korea t Tullahoma, Tennessee 37388 Copyright * 1998 by Sverdrup Technology, Inc. Published by American Institute of Aeronautics and Astronautics, Inc., with permission. INTRODUCTION The government of the Republic of Korea and Korean industry are committed to establishing the capability for future aircraft development in Korea. The scope of this capability includes both military and civil systems. To meet this commitment, wind tunnels of sufficient size and capability are required. Several projects are now underway to support this effort. One of them, a subsonic wind tunnel undertaken by the Republic of Korea Air Force Academy (KAFA), is the subject of this paper. KAFA selected Sverdrup Technology, Lie. as the turnkey supplier of the subsonic wind tunnel, including preliminary and final design and construction services. Final design work has been completed and is covered in the present paper. Construction/installation and commissioning/calibration phases will be completed in 1998, and the results of that work will be presented in a future paper. FACILITY REQUIREMENTS During initial facility planning studies, KAFA configured the Subsonic Wind Tunnel as a closedcircuittype with interchangeable, atmospheric-pressure test sections. To support the Republic of Korea's commitment to aircraft and ground vehicle systems, the main testing activities planned to be conducted in the facility are: • Configuration optimization of aircraft • Development of high hit devices • Wing/body integration American Institute of Aeronautics and Astronautics Copyright© 1997, American Institute of Aeronautics and Astronautics, Inc. • Ground passenger vehicle aerodynamics • Building aerodynamics • Full aircraft component integration • Rotor aerodynamics • Helicopter aerodynamics Facility design requirements were established based on these testing activities. The requirements for test-type, test section size, performance, and flow quality are summarized in Tables 1 and 2. Compared to other mediumand large-size subsonic facilities, the KAFA facility's performance and flow quality requirements are state-of-the-art, and they are appropriate for advanced experimental education programs and aircraft development programs.

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.

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.

The wind tunnel is proper functioning platform for accurate aerodynamic research which helps to provides adequate environment condition around scaled model to the compatible dimension. Wind tunnel data is part of design process that used to design their model. For correcting wind tunnel data of wall and mounting effects very careful techniques are used. But it shows limitation for linear flow approximation. This research paper proposed first part of the project i.e. design calculation and simulation i.e. flow in wind tunnel and checking incompressible flow in test section over an airfoil using CFD software. Test section design in rectangular shape for proposed wind tunnel. Contraction cone has contraction ratios 7 and cross section in rectangular shape. Diffuser design in conical shape with 5° diffusion angle and area ratio 1.33. The design philosophy is discussed along method for wind tunnel calculation is outlined. Using Computational fluid dynamics (CFD), design and simulation of flow parameter are investigated with systematic way in open loop wind tunnel. It shows good quality flow in test section as well as in entire wind tunnel. The proposed wind tunnel is conformed to design and can be used for different test in the field of aerodynamics. Wind tunnel design to achieve 40 m/s speed of air with expected low intensity turbulence level. Analysis of airfoil shows that good flow quality in test section. Lift and drag coefficient plotted against angle of attack.

Systems with large physical size such as wind turbines, aircraft, and ships are dominated by the inertia of the flow. In conventional experimental facilities, a reduction in scale is required, which can introduce viscous effects that are not present at full size. However, if the wind tunnel is operated with a heavy gas, the reduction in scale can be counteracted by an increase in density, and the flow that exists at full size can be recreated accurately. This work describes the design, construction, and basic flow characterization of a heavy gas wind tunnel facility, known as the Compressed Air Wind Tunnel (CAWT), that utilizes pressurized air as the working fluid at pressures up to 35 bar. The tunnel was designed to accommodate relatively large models inside the 1.04 meter-diameter test section while having improved optical access compared to existing facilities of this type. A series of flow characterization tasks were carried out on the completed facility, including quantifying the turbulence intensity and flow uniformity in the tunnel test section. Measurements showed a maximum turbulence intensity of 0.46% and an average of 0.22% across all conditions and locations tested. The maximum velocity non-uniformity between four locations in the test section was 0.36%, which occurred at the lowest tested wind speed of 2.4 m/s. The average non-uniformity across all tested conditions was less than 0.093%. Mapping the facility operating space has now enabled ongoing work examining rotorcraft, marine propeller, and wind turbine performance and wake development with the aim of answering long-standing questions regarding how the fluid dynamics depend on scale or Reynolds number effects.

The design of a new transonic wind tunnel to reproduce bypass aero-engine flow conditions is described. This study has been driven by the interest to investigate and optimize the aero-thermal effects of an air/oil integrated surface heat exchanger placed at the inner wall of the secondary duct of a turbofan. The test section of the intermittent wind tunnel consists of a complex three-dimensional (3D) geometry. The flow evolves over the splitter, duplicated at real scale, as it does in the engine, guided by helicoidally shaped lateral walls. Numerical flow analyses have been used to guide the design of the complete wind tunnel. Zero-dimensional models have been developed to recreate the wind tunnel behaviour. Two- and three-dimensional computations have been performed to optimize the test section and the inlet guide vanes that duplicate the flow downstream of the engine fan. The reproduction of the bypass flow structure has been numerically analysed. Flow computations with and without the presence of instrumentation in the test section have been contrasted. Additionally, the influence of an aerodynamic probe on the flow has been studied numerically. This study should lead to improvements in the thermal management of future aircraft power plants, particularly by taking benefit of the cold bypass air to refrigerate the lubrication oil, without penalizing the propulsive efficiency.

Design and performance of a small-scale aeroacoustic wind tunnel