Wind Tunnel Evaluation Research Articles

Wind Tunnel Evaluation of Spray Nozzle and Droplet Size Effects on Spray Penetration Inside Soybean Plants

HighlightsEffectiveness of four nozzle types was evaluated to deliver spray droplets inside soybean canopy in a wind tunnel.Spray deposition at the bottom part of canopies was significantly lower than the upper part across the test section.Nozzles generating medium and coarse droplet sizes improved spray coverage on the top and middle part of the canopy.Abstract. Adequate spray deposition and penetration of pesticides reaching the lower part of soybean canopy can increase the chance of success to protect plants from diseases and insects, especially when soybean foliage is matured. Therefore, selecting the nozzle type with the most appropriate droplet size plays a significant role in providing the right amount of spray deposition to the right place in plant canopy. The objective of this study was to evaluate the most effective spray nozzle and droplet size distribution to achieve more spray coverage within the soybean canopy under a 2 ms-1 wind-tunnel-controlled wind speed at 0.38 m row spacing. An open circuit wind tunnel with laminar airflow was used to avoid the uncontrollable outdoor weather conditions that often vary when similar experiments are conducted in the field. Four commercial spray nozzles (droplet size): XR11004 (medium), TTJ6011004 (coarse), AITTJ6011004 (very coarse), and AI11004 (extremely coarse) were operated at 275 kPa pressure and sprayed for 3 s to increase the spray droplet density to detect their effects in the soybean canopy. Eleven pots of soybean plants were placed in the wind tunnel test section in three rows along the direction of airflow to simulate the 0.38 m soybean row spacing. For each test run, water sensitive papers (WSP) were placed at three different heights of the soybean canopy (top, middle, and bottom) within 5 soybean plants located 0.15, 0.70, 1.25, 1.80, and 2.40 m downwind from the spray boom. After plants were sprayed, WSP samples were collected to determine the spray coverage. The top of the canopy received the greatest amount of spray coverage, followed by the middle position. Regardless of the nozzle and droplet size, significantly lower amounts of spray deposition were found at the bottom part of the canopy at all the sample collection points along the wind tunnel test section. Overall, the nozzles that generated medium and coarse droplet sizes provided higher levels of spray coverage on the top and middle part of the soybean canopy. Providing adequate coverage in the bottom part of the canopy remained a challenge, which must be addressed in future studies to evaluate additional nozzle types with different droplet size classes under different wind speed and row spacing settings. Keywords: Droplet size spectrum, Nozzle type, Soybean plants, Spray coverage, Spray deposition.

Optimizing vortex-induced vibration suppression in π-shaped girders using wind tunnel testing and CFD analysis

This investigation meticulously explores the vortex-induced vibration (VIV) characteristics in Π-shaped girders within long-span cable-stayed bridges, presenting novel VIV mitigation techniques. Employing detailed wind tunnel evaluations of a 1:50 scale model alongside computational fluid dynamics (CFD) analyses to model the two-dimensional flow around the girder, this study reveals the formation and shedding of vortices behind the railings and main steel girder, which significantly contribute to VIV in such structures. The introduction of horizontal splitter plates, one m in width, in conjunction with two-m-wide V-shaped guide vanes, was found to substantially reduce the VIV amplitude of the Π-shaped girder, minimizing vortex generation on the deck’s sides and dramatically reducing the maximum vertical VIV amplitude from 208.75 mm to only 5.56 mm. CFD simulations confirm the effectiveness of these measures in suppressing Karman vortex street formation, thereby significantly improving downstream airflow characteristics. These findings offer pivotal insights for the advancement of bridge design and the proactive management of VIV, showcasing the potential of integrated aerodynamic modifications to enhance structural resilience and performance.

A Comment on: ‘Wind tunnel evaluation of novel drafting formations for an elite marathon runner’ (2023), by Marro M et al.

A Comment on: ‘Wind tunnel evaluation of novel drafting formations for an elite marathon runner’ (2023), by Marro M <i>et al.</i>

Design, Analysis, and Wind Tunnel Evaluation of Novel Fabric-Covered Rotor Blades in Wind Energy Generation

This paper investigates the performance of a novel fabric-covered rotor blade. The study aims to address the need for cost-effective wind turbine blades by exploring the potential of textile-based materials. The research includes a comprehensive wind tunnel experiment to evaluate the aerodynamic response of the fabric-covered blade, compared to a traditional hard-shell blade. The experimental data are systematically processed and corrected for wind tunnel effects, providing valuable insights into the aerodynamic behavior of the novel blade. The results show that the fabric-covered blade, constructed from PTFE-coated fiberglass fabric, exhibits promising aerodynamic characteristics, with potential applications in reducing manufacturing expenses and enhancing power generation. The study concludes by proposing a novel control strategy leveraging the natural deformation of blades at high wind speeds, suggesting potential applications in limiting power output at high wind speeds. Overall, these findings contribute to the ongoing efforts in developing innovative and cost-efficient solutions for wind energy generation.

Wind Tunnel Evaluation of Plant Protection Products Drift Using an Integrated Chemical–Physical Approach

The use of plant protection products (PPPs) has become fundamental to guarantee excellent field productivity. Nevertheless, their usage presents critical issues, such as the quantity of substances used, the relative toxicity, and the contamination of nearby fields caused by atmospheric drift. This study focuses on the characterization of aerosol droplets of PPPs produced by spraying a chemical marker, fluorescein, with an orchard airblast sprayer equipped with conventional hollow cone (HC) and anti-drift air inclusion (AI) nozzles, using a wind tunnel as a controlled environment. A particle/droplet image analysis was employed to study the droplet production of the nozzles, while a liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis allowed us to evaluate samples collected using a cascade impactor located at 5 m, 10 m, and 20 m from the emission point. Overall, HC nozzles are very accurate at producing specific drop size distributions (DSDs), while AI nozzles produce a much wider DSD, concentrating the largest part of the distributed volume into droplets of a larger size. The marker concentration was much lower for the AI nozzles compared to the HC nozzles; moreover, the two nozzles show a similar trend in the coarse droplet range, while significantly differing in the fine droplet spectrum.

Wind tunnel evaluation of novel drafting formations for an elite marathon runner

Drafting is a strategy in marathon running races that reduces the drag force acting on a designated runner. Drafting involves a formation of athletes, called pacers, running in front of (and sometimes behind) the designated runner. The present experiments evaluated complex formations involving up to seven pacers with the aim of enhancing the performances of an elite marathoner. Wind tunnel measurements with 1/10 scale articulated runner manikins were carried out. First, simple formations with one or two pacers were examined and the results were compared with previous investigations. Second, the runner formations of the Nike Breaking2 and INEOS 1:59 Challenge events whose goal was to break the 2 h marathon barrier were studied. The main finding was the identification of three complex formations of six and seven pacers that allow a drag-force reduction of about 60% with respect to a solo runner and an estimated time saving of 262 s. These results point to how it may be possible to run the fastest marathon ever.

Theoretical and Experimental Evaluation of a Compact Aerosol Wind Tunnel and its Application for Performance Investigation of Particulate Matter Instruments

In this study, we developed a compact low-speed wind tunnel. First, we computationally analysed the flow quality of different wall shapes for the contraction section, the most critical part of a wind tunnel, and selected the design exhibiting minimal boundary layer separation at simulated flow velocities of 2 and 8 km h−1. Then, after constructing the wind tunnel, we experimentally evaluated its overall performance based on different parameters per the United States Environmental Protection Agency (U.S. EPA) guidelines (40 CFR 53.62). The air velocity and turbulence profiles were uniform, displaying ≤ 10% variation in the section we tested. Additionally, we measured the mass concentrations and size distributions of polydisperse dust particles, which were generated by a custom-made rotary dust feeder to ensure the homogeneity of the aerosol, inside the wind tunnel at air velocities of 2 and 8 km h−1 and found ≤ 10% deviation for the mean values across the test section relative to those for the central sampling point. We also assessed the effectiveness of the Well Impactor Ninety-Six (WINS) and Very Sharp Cut Cyclone (VSCC) in the wind tunnel at an air velocity of 8 km h−1 by determining the D50 cutoffs, which, being 2.44 ± 0.05 µm and 2.54 ± 0.05 µm, respectively, fulfilled U.S. EPA’s criteria. Furthermore, we compared the performance of a low-cost sensor against that of a reference instrument in measuring PM2.5 concentrations, and our results agreed with those from previous studies.

Wind-Tunnel Evaluation for an Active Sting Damper Using Multimodal Neural Networks

A harmful oscillation occurring in a wind-tunnel test often leads to the degradation of data quality and the limitation of the test envelope. Therefore, it needs to be avoided. With the aim of solving the vibration problem of the long cantilever sting used in wind tunnels, an active sting damper based on piezoelectric stacks is designed and its principle of controlling vibration is analyzed in this paper. To improve the damping effect and ensure the safety of wind-tunnel tests, a controller based on neural networks that is able to suppress multimodal vibration is detailed and established. A hardware platform composed of various instruments is developed, and related testing software is built to evaluate the damper as well as the control algorithm. Finally, broadband excitation and transonic wind-tunnel tests are carried out to verify the capability of the whole damping system. Experimental results indicate that the amplitude of vibration is dramatically reduced and the test angles of attack are enlarged, which show the superiority of the damper and the control algorithm.

고속버스 공력 설계 요소의 기여도 분석에 관한 풍동 시험 및 해석

고속버스 공력 설계 요소의 기여도 분석에 관한 풍동 시험 및 해석

Design and evaluation of a high-speed aeroacoustic wind tunnel

The high-speed aeroacoustic wind tunnel (HSAWT) at Carleton University is a new facility commissioned with the purpose of facilitating experimental studies of turbulent boundary layer (TBL) induced surface pressure fluctuations. This research is primarily intended for applications related to aircraft cabin noise generation from structures exposed to high-speed flow. This open-jet, blowdown wind tunnel is a unique facility in Canada and one of a few aeroacoustic wind tunnels in the world capable of achieving speeds up to Mach 0.8. Flow is delivered from a nozzle with dimensions of 6.1 cm × 15 cm to a test section enclosed within an anechoic chamber with internal dimensions of 1.9 m × 0.88 m × 1.95 m. This study details the complete design methodology for all major wind tunnel components, including the numerical simulations performed in the validation of the designed components. Results of preliminary test section flow characterization and chamber background noise measurements are discussed. Finally, experimental results of the TBL surface pressure fluctuation spectral behavior developed over a flat test section plate are compared with established data and empirical models available in literature.

Development of polydisperse aerosol generation and measurement procedures for wind tunnel evaluation of size-selective aerosol samplers

Accurate development and evaluation of inlets for representatively collecting ambient particulate matter typically involves use of monodisperse particles in aerosol wind tunnels. However, the resource requirements of using monodisperse aerosols for inlet evaluation creates the need for more rapid and less-expensive techniques to enable determination of size-selective performance in aerosol wind tunnels. The goal of recent wind tunnel research at the U.S. EPA was to develop and validate the use of polydisperse aerosols which provide more rapid, less resource-intensive test results which still meet data quality requirements necessary for developing and evaluating ambient aerosol inlets. This goal was successfully achieved through comprehensive efforts regarding polydisperse aerosol generation, dispersion, collection, extraction, and analysis over a wide range of aerodynamic particle sizes. Using proper experimental techniques, a sampler's complete size-selective efficiency curve can be estimated with polydisperse aerosols in a single test, as opposed to the use of monodisperse aerosols which require conducting multiple tests using several different particle sizes. While this polydisperse aerosol technique is not proposed as a regulatory substitute for use of monodisperse aerosols, the use of polydisperse aerosols is advantageous during an inlet's development where variables of sampling flow rate and inlet geometry are often iteratively evaluated before a final inlet design can be successfully achieved. Complete Standard Operating Procedures for the generation, collection, and analysis of polydisperse calibration aerosols are available from EPA as downloadable files. The described experimental methods will be of value to other researchers during development of ambient sampling inlets and size-selective evaluation of the inlets in aerosol wind tunnels.

Droplet spectra and high-speed wind tunnel evaluation of air induction nozzles

A series of air induction nozzles were tested in a high-speed wind tunnel. Droplet size spectra were measured for four air induction nozzles (IDK-120-01, IDK-120-02, IDK-120-03 and IDK-120-04) each at three spray pressures (0.3, 0.4 and 0.5 MPa) and seven different air velocities (121.7, 153.4, 185.5, 218.4, 253.5, 277.5 and 305.5 km·h⁻¹). The measurement distance (0.15, 0.25 and 0.35 m) from the nozzle orifice was found to be important for the atomization of the droplets. The response surface method was used to analyze the experimental data. The results indicated that <i>D</i>v_0.1 and <i>D</i>v_0.5 of the droplets decreased quasi-linearly with increased wind speed, while <i>D</i>v_0.9 was affected by the quadratic of wind speed. <i>D</i>v_0.1, <i>D</i>v_0.5 and <i>D</i>v_0.9 of the droplets were all proportional to the orifice size, and were not markedly influenced by the spray pressure. The percentage of the spray volume consisting of droplets with a diameter below 100 <font style="font-family:Symbol">m</font>m (%<100 <font style="font-family:Symbol">m</font>m) was found to be quadratically related to wind speed, and was not markedly influenced by the spray pressure and orifice size. However, the effect of the orifice size on the %< 200 <font style="font-family:Symbol">m</font>m could not be ignored.

Wind Tunnel Evaluation on the Performance of Blown Airfoil

This study investigated the performance of blown airfoil. Two types of blown airfoil were developed. The integrated parts of the airfoils were investigated in the subsonic wind tunnel to study the aerodynamic forces. Each airfoil was implemented with a blower at different locations on the upper surface and was tested in the wind tunnel, with different Reynolds numbers, and with and without blower. The results showed that the airfoil with air blower produced a very significant additional 35% lift force compared to airfoil without air blower. The experimental result also exhibited 7% higher lift coefficient for air blower compared to numerical analysis.

432 小型風洞の設計・製作および評価に関する研究(流体工学III)

432 小型風洞の設計・製作および評価に関する研究(流体工学III)

Development and wind tunnel evaluation of a shape memory alloy based trim tab actuator for a civil aircraft

This paper presents the development and wind tunnel evaluation of a shape memory alloy (SMA) based smart trim tab for a typical two seater civil aircraft. The SMA actuator was housed in the port side of the elevator for the purpose of actuating the trim tab. Wind tunnel tests were conducted on a full scale horizontal tail model with elevator and trim tab at free stream speeds of 25, 35 and 45 m s−1, and also for a number of deflections of the elevator (30° up, 0° neutral and 25° down) and trim tab (11° and 21° up and 15° and 31° down). To measure the hinge moment experienced by the trim tab under various test conditions, two miniaturized balances were designed and fabricated. A gain scheduled proportional integral (GSPI) controller was developed to control the SMA actuated smart trim tab. It was confirmed during the tests that the trim tab could be controlled at the desired position against the aerodynamic loads acting on it for the various test conditions.

Design and evaluation of an aeroacoustic wind tunnel for measurement of axial flow fans

An anechoic wind tunnel dedicated to fan self-noise studies has been designed and constructed at the von Karman Institute The multi-chamber, mass flow driven design allows for all fan performance characteristics, aerodynamic quantities (e.g., wake turbulence measurements), and acoustic properties to be assessed in the same facility with the same conditions. The acoustic chamber performance is assessed using the optimum reference method and found to be within the ISO 3745 standards down to 150 Hz for pure tone and broadband source mechanisms. The additional influence of installation effects of an aerodynamic inlet was found to create a scattered sound field only near the source location, while still providing good anechoic results at more distant sound pressure measurement positions. It was found to have inflow properties, span-wise uniformity, and low turbulence intensity, consistent with those desired for fan self-noise studies.

Wind Tunnel and Flight Evaluation of Passive Stabilization of a Cargo Container Slung Load

Wind Tunnel and Flight Evaluation of Passive Stabilization of a Cargo Container Slung Load

Influence of nozzle type and size on drift potential by means of different wind tunnel evaluation methods

46 Wind tunnel measurements were used to measure airborne and fallout spray volumes for 10 different spray nozzles. Drift potential reduction percentages (DPRPs), expressing the reduction of the drift potential compared with the reference spraying, were calculated using the following three different approaches: DPRP V1 was based on calculating the first moment of the airborne spray profile, DPRP V2 integrating the airborne spray profile, and DPRP H integrating the fallout deposit curve. The results showed the expected fallout and airborne spray profiles. For the standard flat-fan nozzles, DPRP V1 values were the highest followed by DPRP V2 and DPRP H . For the low-drift nozzles the opposite trend was found. The larger the ISO nozzle size, the greater the DPRP values for both these nozzle types. For the air-inclusion nozzles, there was close agreement between DPRP V1 , DPRP V2 and DPRP H values. This is important in the interpretation of wind tunnel data for different nozzle types and sampling methodologies.

Evaluation of the EPA Drift Reduction Technology (DRT) Low-Speed Wind Tunnel Protocol

Abstract The EPA’s proposed Drift Reduction Technology (DRT) low-speed wind tunnel evaluation protocol was tested across a series of modified ASAE reference nozzles. Both droplet size and deposition and flux volume measurements were made downwind from the nozzles operating in the tunnel at airspeeds of 1 m/s and 2.5 m/s, following the prescribed protocol. Overall, the data followed anticipated trends with a few unanticipated results observed, which could be addressed in future iterations of the protocol. There were some difficulties meeting the proposed protocol data quality requirements. Refined quality requirements would address this with no detrimental effect to the overall data set. Major concerns, at this point, are the feasibility of the overall protocol as well as the applicability of the final collected data. The protocol was tailored such that the collected data would directly input into a dispersion model (most likely WTDISP). However, not having access to such a model puts into question the validity and practicality of the protocol in its present form. Given the time requirements, which require approximately nine times that of the high speed protocol (90 min versus 10 min, unpublished data), there is a definite need to modify the existing protocol to insure equitable implementation of the overall DRT program.

Wind Tunnel Evaluation of Drift Reduction Potential and Spray Characteristics with Drift Retardants at High Operating Pressure

Abstract Although considerable research has been done on effectiveness of drift retardants for many years, answers to some questions are still unclear to applicators. Laboratory tests were conducted to evaluate drift potentials associated with off-target ground and airborne spray deposits discharged with a hollow cone nozzle spraying three different drift retardants at a high operating pressure and various wind velocities in a wind tunnel. Droplet sizes and spray widths were also determined with a laser imaging system and a portable spray patternator. At 1655 kPa pressure and 4.65 L/m flow rate, the volume median diameters of droplets from the hollow cone nozzle discharging spray mixtures containing water only, polyvinyl polymer, nonionic colloidal polymer and polyacrylamide polymer drift retardants were 201, 222, 239, and 210 μm, respectively. The major spray pattern width was not changed after drift retardants were added into the spray carrier. For the wind velocity from 1 to 5 m/s in the wind tunnel, the polyacrylamide drift retardant produced the highest airborne deposit among the three drift retardants, followed by polyvinyl, and then nonionic colloidal. Also, the polyacrylamide drift retardant produced the highest ground drift potential, followed by nonionic colloidal and then polyvinyl. According to the results from this laboratory study, both nonionic colloidal and polyvinyl polymer drift retardants reduced the drift potential compared to the spray carrier containing water only.