Search

The more economically viable and environmentally sustainable approach for treating the by-products of coal combustion from thermal power plants entails their collective disposal as opposed to individual disposal methods. This aligns with pertinent EU directives and domestic regulations, ensuring compliance with established standards while optimizing resource utilization and minimizing environmental impact. This study evaluated the resistance to wind erosion of the binding properties of a mixture (fly ash (FA), bottom ash (BA), and additives) using an indoor wind tunnel under simulated ambient conditions. Investigations of the mutual impact of ash, bottom ash, and additives (CaO and Ca(OH)2) with a certain percentage of water were carried out with eighteen samples. The samples consisted of the water at six addition rates 5, 8, 10, 15, 20, and 25% (w/w), and additive at three addition rates (1, 2, and 3% (w/w). Based on the obtained results, the optimal ratios of additives (3% (w/w)) and water (15% (w/w)) were determined. Prior to the wind tunnel experiments, and according to the different addition rates of additives and water, eight samples were prepared with different addition rates of ash. The mass concentrations of suspended particles (PM10) and total suspended particles (TSPs) in these samples were measured at three distinct wind velocities: 1 m/s, 3 m/s, and 5 m/s, respectively. The results indicate that the samples containing the optimal content of additives and water demonstrate a maximum increase in PM10 emission zero values of no more than 1.9 times. This finding can be considered satisfactory from the standpoint of environmental protection. [ABSTRACT FROM AUTHOR]

Simple Summary: This study addresses global food security by highlighting the challenge of protecting food losses from insect damage. To find effective low-risk ways to manage these pests, we assessed the avoidance of the red flour beetle, a common pest in stored grains, to essential oils. Through various experiments in the laboratory, we investigated the beetles' behavioral response to different scented oils. While no definitive repellent was identified, this study sheds light on factors influencing insect behavior and the need for further research in behaviorally based management tactics such as avoidance. Ultimately, this work aims to develop strategies to protect stored grains, contributing to global food security efforts. Background: Food security is an increasingly pressing global issue, and by 2050, food production will not be sufficient to feed the growing population. Part of global food insecurity can be attributed to post-harvest losses, including quantity and quality losses caused by stored-product pests like insects. It is thus timely to find management strategies to mitigate these losses and counteract food insecurity. The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a global stored-product pest with a wide range of food sources, was used in this study to assess repellency to a selection of essential oils. Methods: Multiple behaviorally relevant methods were used to determine the efficacy of the essential oils in assays to pinpoint the most promising repellents. Experiments were used to assess individual and group behaviors with or without airflow and examined the behavioral variation in distance moved and the time spent away from the oil. Results: It was found that exposure to essential oils and conditions of experimentation considerably influenced T. castaneum's behavioral response, but a clear candidate for repellency could not be chosen based on the collected data. Conclusions: Follow-up research is needed to pinpoint repellents for integrated pest management practices to protect grains from stored-product pests and to justify their use in and around commodities. [ABSTRACT FROM AUTHOR]

This work explores the response of a cantilever plate attached to a cylinder in a wind tunnel under an impact excitation. A detailed computer-aided design (CAD) model and the finite element analysis (FEA) modal simulation of the experimental setup are introduced. Two experimental techniques are thoroughly discussed: an accelerometer-based experimental modal analysis (EMA) method, and a non-contact, full-field, high-speed digital image correlation (DIC)-based operational deflection shape (ODS) analysis method. The experimental and FEA results of the first seven natural frequencies, mode shapes, and ODSs of the cantilever plate are presented and compared. The percent differences between the EMA and FEA natural frequency results are less than 4.8%, and the modal assurance criterion (MAC) values between the EMA and FEA mode shapes are at least 0.845. The percent differences between the ODS analysis and FEA natural frequency results are less than 3.4%, while the MAC values between the ODS analysis ODSs and FEA mode shapes are at least 0.728. The percent differences between the EMA and ODS analysis natural frequency results are less than 3.5%, and the MAC values between the EMA mode shapes and ODS analysis ODSs are at least 0.505. There are two sets of two different mode shapes and ODSs with relatively high correlation. One set is a set of two closely spaced modes and ODSs approximately 20 Hz apart with obvious similarities in shape. The other set is a set of two modes and ODSs approximately 100 Hz apart that share less obvious similarities in shape. [ABSTRACT FROM AUTHOR]

Wind from all directions Wind loads on membrane structures are not regulated by standards. The variety of shapes of the typically open and thus flow‐exposed surfaces on both sides cannot be captured using geometric variables in tables, as is common for typical building forms in Eurocode EN 1991‐1‐4. The recommended individual wind tunnel tests are only feasible for larger projects with the corresponding budgets and planning periods. Therefore, some recommendations for typical membrane roofs have been collected in the literature, and at the same time, computer‐based wind simulations have developed to the extent that they are now also offered in market‐standard FEM software packages. This paper aims to explain the accuracy and comparability of the various approaches using case studies. The paper presents the analysis of standard approaches, literature values, wind tunnel tests, and computer‐based methods with a comparison of calculation results and provides insights into the development of load assumptions in membrane construction. [ABSTRACT FROM AUTHOR]

Neglecting the velocity reduction in the induction zone of wind turbines can lead to overestimates of power production predictions, and, thus, of the annual energy production for a wind farm. An experimental study on the induction zone associated with wind turbine operations is performed in the boundary‐layer test section of the BLAST wind tunnel at UT Dallas using stereo particle image velocimetry. This experiment provides a detailed quantification of the wind speed decrease associated with the induction zone for two different incoming flows, namely, uniform flow and boundary layer flow. Operations of wind turbines in different regions of the power curve are modeled in the wind tunnel environment with two porous disks with a solidity of 50.4% and 32.3%, which correspond to thrust coefficients of 0.71 and 0.63, respectively. The porous disks are designed to approximate the wake velocity profiles previously measured for utility‐scale wind turbines through scanning wind LiDARs. The results show that the streamwise velocity at one rotor diameter upwind of both disks decreases 1% more for the boundary layer flow than for the uniform flow. Further, the effect of shear in front of the disk with a higher thrust coefficient can be observed until 1.75 rotor diameter upwind of the disk, whereas for the disk with a lower thrust coefficient, the effect of shear becomes negligible at 1.25 rotor diameter upwind. It is found that at one rotor diameter upwind, for both incoming flows, the disk having a higher thrust coefficient has 2% more velocity reduction than the lower‐thrust‐coefficient disk. The results suggest that the variability in wind shear and rotor thrust coefficient, which is encountered during typical operations of wind turbines, should be considered for the development of improved models for predictions of the rotor induction zone, the respective cumulative effects in the presence of multiple turbines, namely, wind farm blockage, and more accurate predictions of wind farm power capture. [ABSTRACT FROM AUTHOR]

The immediate vicinity of buildings of different floors causes damages of the smoke and ventilation channels work of the low-rise buildings. This is dangerous for the resident's health and lives. To determine the impact of high-rise buildings on the operation of air channels of a nearby two-story building, experimental research has been carried out in a wind tunnel. Charts and analytical formulas have been designed for determining the buildings aerodynamic coefficients depending on wind directions and the channels height. An increase of the channel height results in an increase in static rarefaction in smoke and ventilation channels. Increasing rarefaction increases the efficiency of the natural ventilation system and ensures the residents health and life. [ABSTRACT FROM AUTHOR]

Chemical warfare agents (CWAs) pose a threat as gaseous substances and as liquid aerosols, necessitating chemical warfare-protective clothing for soldiers. The paramount consideration lies in the effectiveness of the clothing as a barrier against the pertinent CWAs. This paper presents a dynamic swatch test method aimed at evaluating the performance of such clothing against liquid-phase aerosol penetration. Central to the methodology is a specialized test cell designed to rotate to the left and right, integrated within a laboratory wind tunnel, replicating mission-relevant conditions with varying wind speeds. Utilizing di(2-ethylhexyl) sebacate particles as liquid aerosols, tests were conducted at wind speeds of 1.0, 3.0, and 5.0 m/s. Penetration assessment relied on analyzing particle counts downstream and upstream of the fabric, with preliminary studies showing that higher wind speeds and fabric air permeabilities increase penetration at an equivalent face velocity of 5.0 cm/s. Interestingly, penetration decreased when fabric samples were subjected to rotation. The system and methodology devised demonstrated consistent and repeatable results, offering valuable insights into optimizing the effectiveness of chemical warfare-protective clothing. This research contributes to advancing methodologies for testing protective clothing, crucial for ensuring the safety of military personnel in hazardous environments. [ABSTRACT FROM AUTHOR]

In arid regions, the use of ridge cover as a traditional agricultural strategy has been effective in mitigating soil wind erosion. However, few studies have focused on the sand transport characteristics of different micro‐ridge spacings and heights. This study aimed to identify the mechanism by which ridges change the near‐surface sand transport. In a controlled wind tunnel environment, the aeolian sand flux structure and sand transport flux (qz) at heights from 0 to 0.7 m were measured. The results showed that, compared with no ridges, ridge covering could significantly modify the structure of aeolian sand flux near the surface, yielding a substantial reduction in the proportion of sand transport to the total sand transport in the 0‐ to 0.1‐m height layer. In the absence of ridges, blown sand was mainly concentrated in the 0‐ to 0.1‐m height layer, and qz decreased exponentially as the height increased. With various micro‐ridge spacings and heights, when H was less than 0.1 m and L was more than 15H, the blown sand also remained concentrated in the 0‐ to 0.1‐m height layer, and qz decreased exponentially as the height increased. When H increased to 0.15 m from 0.1 m and L decreased from 15H to 5H, the height of the blown sand was concentrated in the 0.3‐ to 0.4‐m layer. The blown sand layer of most ridge structures was concentrated at a height of 0.1–0.4 m, and the structure of the aeolian sand flux resembled an 'elephant nose effect'. The total sand transport rate of all ridge structures was significantly lower than that with no ridges, indicating that a reasonable ridge structure can effectively prevent wind erosion. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Neglecting the velocity reduction in the induction zone of wind turbines can lead to overestimates of power production predictions, and, thus, of the annual energy production for a wind farm. An experimental study on the induction zone associated with wind turbine operations is performed in the boundary‐layer test section of the BLAST wind tunnel at UT Dallas using stereo particle image velocimetry. This experiment provides a detailed quantification of the wind speed decrease associated with the induction zone for two different incoming flows, namely, uniform flow and boundary layer flow. Operations of wind turbines in different regions of the power curve are modeled in the wind tunnel environment with two porous disks with a solidity of 50.4% and 32.3%, which correspond to thrust coefficients of 0.71 and 0.63, respectively. The porous disks are designed to approximate the wake velocity profiles previously measured for utility‐scale wind turbines through scanning wind LiDARs. The results show that the streamwise velocity at one rotor diameter upwind of both disks decreases 1% more for the boundary layer flow than for the uniform flow. Further, the effect of shear in front of the disk with a higher thrust coefficient can be observed until 1.75 rotor diameter upwind of the disk, whereas for the disk with a lower thrust coefficient, the effect of shear becomes negligible at 1.25 rotor diameter upwind. It is found that at one rotor diameter upwind, for both incoming flows, the disk having a higher thrust coefficient has 2% more velocity reduction than the lower‐thrust‐coefficient disk. The results suggest that the variability in wind shear and rotor thrust coefficient, which is encountered during typical operations of wind turbines, should be considered for the development of improved models for predictions of the rotor induction zone, the respective cumulative effects in the presence of multiple turbines, namely, wind farm blockage, and more accurate predictions of wind farm power capture.

Abstract Chemical warfare agents (CWAs) pose a threat as gaseous substances and as liquid aerosols, necessitating chemical warfare-protective clothing for soldiers. The paramount consideration lies in the effectiveness of the clothing as a barrier against the pertinent CWAs. This paper presents a dynamic swatch test method aimed at evaluating the performance of such clothing against liquid-phase aerosol penetration. Central to the methodology is a specialized test cell designed to rotate to the left and right, integrated within a laboratory wind tunnel, replicating mission-relevant conditions with varying wind speeds. Utilizing di(2-ethylhexyl) sebacate particles as liquid aerosols, tests were conducted at wind speeds of 1.0, 3.0, and 5.0 m/s. Penetration assessment relied on analyzing particle counts downstream and upstream of the fabric, with preliminary studies showing that higher wind speeds and fabric air permeabilities increase penetration at an equivalent face velocity of 5.0 cm/s. Interestingly, penetration decreased when fabric samples were subjected to rotation. The system and methodology devised demonstrated consistent and repeatable results, offering valuable insights into optimizing the effectiveness of chemical warfare-protective clothing. This research contributes to advancing methodologies for testing protective clothing, crucial for ensuring the safety of military personnel in hazardous environments.

Deployable hind wings of beetles led to a bio-inspired idea to design deployable micro aerial vehicles (MAVs) to meet the requirement of miniaturization. In this paper, a bionic deployable wing (BD-W) model is designed based on the folding mechanism and elliptical wing vein structure of the Protaetia brevitarsis hindwing, and its structural static and aerodynamic characteristics are analyzed by using ANSYS Workbench. Finally, the 3D-printed bionic deployable wing was tested in a wind tunnel and compared with simulation experiments to explore the effects of different incoming velocity, flapping frequency, and angle of attack on its aerodynamic characteristics, which resulted in the optimal combination of the tested parameters, among which, the incoming velocity is 3 m/s, the flapping frequency is 10 Hz, the angle of attack is 15°, and the lift-to-drag ratio of this parameter combination is 4.91. The results provide a theoretical basis and technical reference for the further development of bionic flapping wing for MAV applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Developing the technique of Acoustic travel time TOMography (ATOM) for monitoring the indoor air temperature and airflow measurements represents a significant breakthrough for modern buildings especially those prioritizing thermal comfort. While conventional measurement methods are limited to individual measuring points, ATOM technique can measure the climatic parameters' distribution across the entire room with high spatial resolution utilizing sound velocity measurements along various propagation sound paths. This research outlines the ongoing development of the ATOM technique for simultaneous measuring the indoor air temperature and airflow velocity at the Department of Building Physics at the Bauhaus‐University Weimar. It presents both the challenges confronted and the solutions developed in establishing a straightforward measuring system that can optimally fulfil the requirements of the indoor climate projects. [ABSTRACT FROM AUTHOR]

The Aeroacoustics Laboratory in the Department of Aerospace Engineering at Penn State currently serves several areas of experimental research. Most notable in the laboratory is the Anechoic Chamber of which the Aeroacoustics Wind Tunnel is an integral part. In recent years the dominant areas of research have included model aircraft exhaust jets and model rotors for helicopter applications involving detailed noise experiments. In the jet noise area, the applications have included aircraft in both flyover and take-off configurations. In the flyover application the air flow surrounding the exhaust jet has a significant effect on the radiated noise and must be simulated to produce experimental results that will be most useful in preliminary design of noise suppression applications. The Aeroacoustics Wind Tunnel at Penn State serves the purpose for this simulation. During aircraft take-off, the aircraft airspeed is in a range exceeding 250 ft per second, or Mach number of over M = 0.22. In the years preceding 2022, the velocity of the free jet flow of the Penn State facility was limited to less than 200 ft/sec. This paper reports on a project to design upgrades to the existing wind tunnel to improve the test section flow velocity to values closer to the 250 ft/sec target. The approach began with a preliminary design of the return flow ducting to convert the open jet, open return wind tunnel to a closed return tunnel. The concept is to make use of the flow energy in the exhaust of the tunnel to boost the input energy to the inlet fan that drives the flow to the test section. An integral part of the preliminary design involved making use of an upgraded flow analysis computer code to predict the gain in test section velocity of the new facility. For the available horsepower of two fans in the facility, the configurations of the existing and upgraded wind tunnel were entered into this analysis code based on a quasi-one-dimensional formulation. The code included empirical data formulated to include the various shapes of the components of the tunnels. The relative flow velocities in each section used simple incompressible continuity to calculate all velocities in the component sections. The average dynamic pressure in each section is calculated from the flow (constant) density and the velocity squared. Each section had a non-dimensional pressure loss parameter calculated from empirical data (from the relevant literature). The basic code (using the Excel algorithms) was based on a predictor-corrector concept in which the calculation was initialized with the estimated velocity and pressure of the flow at the entrance to the test section. The loss in each following section is estimated to determine the loss in the total pressure and the cumulated loss compared to the gains made at the two fans in the circuit. The initial guess is adjusted based on the total pressure value at the end of the circuit. During the related experiments, measurements of the total and dynamic pressure were performed at several joints between sections and compared to the values predicted in the analysis code. Various settings of the horsepower of the drive fans were used and the results were compared to flow measurements for the tunnel configurations (predominantly for the open return and closed return tunnel setups available before and after the upgrade project.) Results of the analysis and experiments are presented and analyzed together with the remaining activities planned for the coming months. [ABSTRACT FROM AUTHOR]

Climate significantly affects the performance of building materials and its changing patterns are posed to increasingly exacerbate the projected impacts. Prevention strategies are indeed necessary to ensure avoiding excessive degradation and serious damage to the built environment. In this context, innovative and accessible methodologies and tools are required to investigate and characterize the interaction between material properties and climatic factors. This paper presents an innovative device for the simulation of natural ventilation, relative humidity and temperature fluctuations and for evaluating the performance of building materials subjected to different environmental scenarios. The presented results include the design, construction and validation of a small-scale wind tunnel (2 m × 1.8 m ca. vertical orientation). Key findings outline the adequacy of the tool in reproducing a stable, quality airflow with the following characteristics: achievable operational airflow speed ranges between 0.2 and 0.7 m/s, safe operational temperature is included between 10℃ and 35℃ and allowable operational relative humidity varies between 30 and 99%. Advantages and limitations for laboratory applications are outlined in the paper and future work is also suggested. [ABSTRACT FROM AUTHOR]

Ceratitis capitata Wiedmann (Diptera: Tephritidae) is a significant pest of apricot (Prunus armeniaca) fruit in the spring and summer seasons in Türkiye. New integrated pest management techniques are required to reduce dependency on insecticides used for its control that may result in adverse environmental impacts. In the current study, we analyzed the volatiles emitted by apricot fruit using gas chromatography-mass spectrometry (GC-MS). We tested the behavioral responses of C. capitata to some of the identified compounds in the laboratory. Our results demonstrated that in four-arm olfactometer bioassays, C. capitata was more attracted to cis-3-hexenyl acetate and ethyl acetate than (Z)- 2-hexenyl butyrate and the control. In the wind tunnel, the landing rate on cis-3-hexenyl acetate was higher than those on (Z) -2-hexenyl butyrate and ethyl acetate. Our findings may support the development of attractants for novel control strategies against C. capitata in orchards. [Display omitted] • According to odor characterization results by SPME and GC-MS, 63 compounds were isolated from apricot volatiles. • The predominant volatile components were found to be cis -3-hexenyl acetate, ethyl acetate, and (Z)- 2-hexenyl butyrate. • Laboratory experiments confirmed that 3 compounds attracted more flies than the control. • The predominant volatile components of apricot can be a source of new Medfly kairomones as attractants of this pest. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The accurate simulation of wind flow in the atmospheric boundary layer in a wind tunnel is crucial for various engineering applications, spanning fields such as civil and environmental engineering. With the aim of investigating and characterizing the behavior and impact of wind on scaled models of civil structures in the Wind Tunnel of the School of Civil Engineering at the University of Valle, the main objective is to determine the appropriate distribution of turbulence-generating devices to replicate specific velocity profiles required for rural, suburban, and urban exposure types that describe the atmospheric boundary layer. This study is based on reproducing three velocity profiles, representative of urban, suburban, and rural exposures, at a 1:200 scale. To achieve this, full-scale Irwin vortex generators, a castellated barrier, and Counihan and Gartshore roughness elements were implemented. Velocity measurements in the wind tunnel test section were conducted using a hot-wire anemometry system and Pitot tubes. Experimental results obtained by simulating velocity profiles demonstrated an acceptable correspondence with theoretical profiles established in the NSR-10 design code. This study contributes to the advancement in understanding and replicating velocity profiles in the context of simulating the atmospheric boundary layer in wind tunnels in Colombia, supporting key applications in the field of engineering. [ABSTRACT FROM AUTHOR]

Sand-cemented bodies (SCBs) are naturally distributed in some interdune corridors in the central Taklimakan Desert, northwest China. In this study, field-collected SCB particles were used as the experimental material, and wind tunnel experiments were conducted with different sand supplies, wind velocities, and SCB coverages to evaluate SCB wind erosion efficiency and vertical mass flux. The results showed that wind erosion efficiency decreased as SCB coverage increased. When the SCB coverage was above 40%, sand deposition processes occurred only under saturated sand flow, while sand transport remained unaffected by increases in SCB coverage under unsaturated sand flow. Under saturated flow, the highest concentrations of transported sand were found at 0–6 cm above the surface, and the main sand bed process was deposition. The sand bed process changed from aeolian erosion to deposition with increasing SCB coverage and tended to remain stable until the SCB coverage exceeded 40%. By contrast, under unsaturated sand flow, the sand bed process was primarily aeolian erosion, and the highest concentrations of transported sand were found at 0–4 cm above the surface. At high SCB coverage levels (more than 40%), a general balance between aeolian erosion and deposition processes was reached. In summary, increasing SCB coverage had a significant impact on surface wind erosion processes. Thus, SCBs can be used as a novel sand retention material. [ABSTRACT FROM AUTHOR]

Accurate prediction of Mach numbers is of paramount importance in wind tunnel experiments. While ensemble prediction models have shown promising performance compared with single-model approaches, existing ensemble methods often prioritize ensemble generation while neglecting the critical aspect of ensemble fusion. This oversight has led to suboptimal precision in Mach number prediction. In this paper, we address this issue by proposing a novel approach that leverages metalearning for ensemble fusion. By incorporating metalearning techniques, our framework effectively combines the strengths of multiple base learners to enhance predictive accuracy. Extensive experiments conducted on a comprehensive data set demonstrate the superiority of our proposed approach over traditional ensemble methods. The results highlight the significance of ensemble fusion in achieving high-precision Mach number prediction in wind tunnel experiments. This research contributes to the advancement of ensemble modeling by emphasizing the importance of fusion techniques and provides valuable insights for improving ensemble prediction models in various domains. [ABSTRACT FROM AUTHOR]

This study investigated the impact of wing design on the performance of the Cessna 172-R aircraft, focusing on modifications to its wing geometry. The study proposes two alternate configurations: one with increasing the span length and retaining the existing chord length, and the other with increasing the chord length retaining the existing span length. Experimental and analytical studies were conducted to evaluate the performance of these two configurations. The study found that the modified wingspan configuration significantly enhanced the aircraft's performance, with an increase in lift coefficient, range, and endurance by 13.2%, 26.15%, and 29.26%, respectively. Additionally, the drag coefficient was decreased by 8.12%, indicating the potential for reduced fuel consumption and operational costs. In contrast, the modified wing chord configuration did not improve the performance output. These findings underscore the critical role of wing design in aircraft performance and highlight the potential for modifications to wing geometry to provide significant improvements in efficiency and operational cost. The results of this study indicate the scope for further research in this area, with efforts to optimize aircraft performance and reduce environmental impact. [ABSTRACT FROM AUTHOR]

An extensive series of wind-tunnel experiments were conducted in the Boundary Layer Wind Tunnel (BLWT) Experimental Facility (EF) at the University of Florida (UF) to investigate the effect of heterogenous terrain on wind flow and pressure distributions on building surfaces. Many studies have already been performed on the effect of upwind terrain on wind characteristics and wind loads on buildings. Previous tests in wind tunnels were mainly designed for uniform upwind terrain or simple two-dimensional roughness changes (e.g., smooth-to-rough change or vice versa). Using the wind-tunnel facility at the UF, we were able to perform an extensive series of tests on heterogeneous upwind terrains. The first part of the testing was focused on wind characteristics by measuring the three components of wind velocity when wind flow passed over different complex upwind terrains. The second part of the testing was intended to obtain the aerodynamic loads of wind over complex terrains on low-rise and midrise building models. The data and metadata are publicly available on the DesignSafe-CI repository under the DOI of 10.17603/Ds2-6hg9-R131. Researchers and practicing engineers can use the collected data to understand the effect of heterogeneous upwind terrain better. [ABSTRACT FROM AUTHOR]

The global annual death toll due to drowning is of the order of 105. Rescue and search operations in urban rivers show a low rate of success. Operational computational drift models have been developed for marine environments but not for the case of river drowning. In the latter case, no scale separation occurs between the body and flow length scales. To model them, three hydrodynamic force coefficients of representative bodies, such as drag, side and lift coefficients, are needed. So far, their value was not characterized for the typical positioning of the body of a drowning victim. In this work, we used full-scale laboratory experiments to identify the range of value of these hydrodynamic coefficients based on 249 tests conducted in a wind tunnel. Observations in the air can be transferred to water environment thanks to flow similarity. For the typical body positioning of a drowning victim, the drag coefficient was found to vary in the range 0.5–1.2. Changing the yaw angle of the body, induces variations in the drag coefficient by about 50%. Considering loose clothes instead of tight clothes leads to an increase in the drag coefficient by about 30%, whereas adding a backpack has a limited influence (less than 5%). With the available experimental setup, it has been difficult to detect distinctive patterns and trends for the side and lift coefficients. This study is part of a multidisciplinary effort for developing scientific knowledge and technologies contributing to a reduction of drowning-induced fatalities in rivers. [ABSTRACT FROM AUTHOR]

Featured Application: Wind-tunnel tests of 3D-printed soccer balls with various surface features are used to create an equation that predicts the critical Reynolds number. Eight balls were manufactured with a 3D printer to resemble various types of 32-panel soccer balls. One ball was completely smooth, whereas the other seven possessed various dimple patterns on their surface panels. Seam width and seam depth were also varied. Wind-tunnel experiments were performed to extract aerodynamic coefficients, and also to determine the critical Reynolds number for each manufactured ball. A new surface roughness parameter is introduced, and a fitting formula is presented, which allows for the prediction of the critical Reynolds number if the new parameter is known. [ABSTRACT FROM AUTHOR]

This study aims to experimentally investigate the effects of parallel blade–vortex interaction (BVI) on the aerodynamic performances of an airfoil, in particular as a possible cause of blade stall, since similar effects have been observed in literature in the case of perpendicular BVI. A wind tunnel test campaign was conducted reproducing parallel BVI on a NACA 23012 blade model at a Reynolds number of 300,000. The vortex was generated by impulsively pitching a second airfoil model, placed upstream. Measurements of the aerodynamic loads acting on the blade were performed by means of unsteady Kulite pressure transducers, while particle image velocimetry (PIV) techniques were employed to study the flow field over the blade model. After a first phase of vortex characterisation, different test cases were investigated with the blade model both kept fixed at different incidences and oscillating sinusoidally in pitch, with the latter case, a novelty in available research on parallel BVI, representing the pitching motion of a helicopter main rotor blade. The results show that parallel BVI produces a thickening of the boundary layer and can induce local flow separation at incidences close to the stall condition of the airfoil. The aerodynamic loads, both lift and drag, suffer important impulsive variations, in agreement with literature on BVI, the effects of which are extended in time. In the case of the oscillating airfoil, BVI introduces hysteresis cycles in the loads, which are generally reduced. In conclusion, parallel BVI can have a detrimental impact on the aerodynamic performances of the blade and even cause flow separation, which, while not being as catastrophic as in the case of dynamic stall, has relatively long-lasting effects. [ABSTRACT FROM AUTHOR]

For the first time, this paper examines the aerodynamic forces that arise in a platoon of Heavy Goods Vehicle lorries travelling in close proximity during an overtaking manoeuvre. Through an in-depth programme of wind tunnel experiments it is demonstrated that there is a complex relationship between the drag and side force coefficients, with a possible hysteresis-like behaviour shown. The influence of the overtaken lorry on the overtaking lorry is shown to be key in terms of the aerodynamic-induced forces experienced by the latter. Furthermore, the overtaking lorry is shown to benefit aerodynamically from the overtaken lorry, and this is attributed to the elliptical nature of the Navier-Stokes equations. In addition to examining the forces that arise during overtaking, the variation of the wind-induced forces with respect to yaw on a single lorry is compared to those on a middle lorry in a 3-lorry platoon. The aerodynamic benefits arising from platooning/vehicles travelling in close proximity are again demonstrated, although it is shown that these benefits may only exist over a limited range of yaw angles, raising questions about the real-world application of this approach. This has important implications for platooning in crosswinds and the drag force reduction that is assumed due to platooning. [ABSTRACT FROM AUTHOR]

In experiments in a wind tunnel, oscillations of three prisms with a rectangular cross section are studied. The prisms are located perpendicular to the velocity vector of the incoming flow and are limited from the ends by end plates that prevent air flow. The elastic suspension allows body oscillation with six degrees of freedom. It turned out that under the action of the air flow, two modes of oscillation of prism realized: translational oscillations in the direction perpendicular to the generatrix of prismatic bodies and the flow velocity, and rotational oscillations around an axis that is parallel to the generatrix, passes through the center of the prism and is perpendicular to the velocity of the incoming air flow. The tension of the two springs included in the elastic suspension is measured by the strain gauge method during the oscillation. The calibration experiment makes it possible to link the amplitudes of spring tension oscillations and phase shift with the amplitudes of rotational and translational oscillations of prisms. It turned out that a prism with a height-to-width ratio of 0.22 in the flow is subject to rotational oscillations. An increase in the ratio of height to width to 0.36 leads to a decrease in the amplitude of rotational oscillations and the appearance of translational ones. The ranges of existence of rotational and translational oscillations overlap. A further increase in the ratio of height to width to 0.43 is accompanied by intensive translational galloping. [ABSTRACT FROM AUTHOR]

This study aims to investigate the inrun position in ski-jumping, in search for factors increasing the inrun speed without compromising the take-off. The inrun position of eight World Cup (WC) and fifteen Continental Cup (COC) ski jumpers were investigated in a wind tunnel at NTNU. A preferred position, replicating a jumper's position in competition, was measured for each athlete. Improvements, based on common sense aerodynamics, with the aim to improve the aerodynamic drag were executed. The aerodynamically best of these was compared with the preferred position. A numerical model simulating the inrun speed in ski-jumping hills was used to evaluate the impact the results will have in different hill sizes, for comparisons of drag measurements and inrun speed in competitions. In the preferred position, COC had 15.5% higher drag area than the WC athletes. In their best tested position, a group difference of 10.8% was found. These differences correspond with speed differences between 0.4 and 1.3 kmh−1, or 1–3 gates (as found by the numerical model). Group difference in drag was explained by a larger trunk angle for COC. Both groups improved from their preferred to their best position, due to reductions in thigh and leg angle. [ABSTRACT FROM AUTHOR]