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Due to the advantages of Laplace domain in both time and frequency domains, the dynamic analysis and control tools in engineering software like MATLAB and Python have been designed based on it. Dynamic analysis of structures requires determination of the overall transfer matrix, which is obtained by multiplying the structure's transfer matrix (TM) with the load TM. With the input vector of unit intensity white-noise processes and the overall TM, the structural responses can be obtained. Furthermore, having the load TM is crucial for implementation of active control systems. In this article, the TM of along-wind loads was estimated for a tall building using the proper orthogonal decomposition (POD) method and the genetic algorithm (GA). To evaluate the effectiveness of the proposed approach, an example of a tall building was provided. The wind load cross-power spectral matrix (XPSD) was decomposed using POD technique, followed by the truncation of higher loading modes. Subsequently, the loading TM was derived by estimating the target non-linear functions with linear transfer functions through GA technique. Then, the responses of the structure were computed using the loading TM. The results demonstrated the efficacy of the proposed method in acquiring the loading TM and predicting wind-induced responses. [ABSTRACT FROM AUTHOR]

This paper presents a unique study on the dynamic identification of the tallest glue-laminated timber frame building in the world using forced vibration tests (FVTs) and long-term ambient vibration tests (AVTs). Because the amount of sway in service under wind has become the governing design criterion for tall timber buildings, this paper aims to provide useful information and evaluate available tools and methods for modal identification in tall glulam timber frame buildings. First, combined operational modal analysis schemes based on the variational mode decomposition with the stochastic subspace identification and the random decrement technique were adopted to identify the modal properties from nonstationary ambient data. Then, unique full-scale forced vibration tests were conducted using two different methods to excite the building: measured electrodynamic shakers excitation and unmeasured rhythmic human-induced excitation. Finally, a finite-element (FE) model of the tall glulam frame building was developed and frequency response function (FRF)–based model updating was conducted showing that the FE model was able to predict the modal behavior of the test building. The results show that natural frequencies identified from output-only techniques are in good agreement with the FVT results. Damping ratios obtained from both AVTs and FVTs exhibited amplitude-dependent behavior with a larger variation observed in the FVT results due to larger range of response amplitudes. These results have significant consequences for the design of tall timber buildings under serviceability-level loading, where damping plays an important role. The resulting damping ranges presented in this paper can serve as a useful guideline for practicing engineers in developing their prediction models of tall timber buildings under serviceability-level loading. [ABSTRACT FROM AUTHOR]

Wind is one of the main factors causing variable actions in tall buildings, and its effects cannot be neglected in the evaluation of either displacements and accelerations that develop in the structure or the internal forces generated indirectly within. However, the structural analyses necessary for these evaluations usually lead to high computational efforts, so surrogate models have been increasingly used to reduce the computational time required. In this work, five machine learning techniques are evaluated for predicting maximum displacement in buildings under dynamic wind loads: k-nearest neighbors (kNN), random forest (RF), support vector regression (SVR), Gaussian process regression (GPR), and artificial neural network (ANN). An initial dataset with 500 random samples was used to evaluate the responses generated by the models. The predictor variables were the building's height, width, and length; average density; damping ratio; wind velocity; and ground roughness. The obtained results demonstrate that the techniques can predict dynamic responses, mainly the GPR and the ANN. [ABSTRACT FROM AUTHOR]

Recently, the phenomenon of tail-sustained swaying of the 160 km/h EMU in single-track tunnels has gained much attention, especially for the rear-powered vehicle. This phenomenon is investigated from the perspective of aerodynamic fluid–structure coupling vibration in this study. The aerodynamics simulation model of the train in tunnels and the multi-body dynamics model of the rear-powered vehicle were respectively established through the software of XFlow and Simpack, and then the fluid–structure coupling vibration was simulated by using real-time data dynamic exchange between the two models. Moreover, the carbody's vibration acceleration and the aerodynamic loads acting on the carbody under various wheel–rail contact geometrical conditions were discussed. Finally, the train tail swaying in field was tested, and the dominant frequencies were analyzed. The results show that the periodic aerodynamic loads and the frequency locking effect caused by the coupled vibration are the main factors for ride comfort deterioration. The violent vibration caused by fluid–structure coupling is named vortex-induced vibration (VIV) in some industries such as bridge and submarine pipeline. For the vehicle in this work, with the decrease of equivalent conicity in wheel–rail contact, the amplitude of carbody swaying increases owing to the carbody hunting, which enhances the fluid–structure coupling vibration, and further deteriorates the ride comfort. The swaying of the carbody is dominated by the vehicle hunting frequency, and the improvement of vehicle lateral stability can weaken this phenomenon. [ABSTRACT FROM AUTHOR]

• A new modeling approach for compressor blades is proposed by the Timoshenko beam theory. • The dynamic model of cracked blades is proposed considering the stiffness nonlinearity induced by breathing cracks. • The modeling method is verified by experiments and the proposed dynamic model is validated using ANSYS software. Aero-engine blades may crack under harsh operating environments. This reduces the reliability of the aero-engine and causes catastrophic accidents. Although dynamic modeling and vibration characteristics of simplified blades with cracks have been analyzed extensively, there are few studies on the actual compressor blade with varying sections and twisted shapes. Based on Timoshenko beam theory, a new modeling approach for the compressor blade is proposed. Next, according to the strain energy release rate and Castingliano theory, the dynamic model of cracked compressor blades is established considering the stiffness nonlinearity induced by the breathing crack. The modeling approach is validated by the measured natural frequencies of an intact blade. Then, the dynamic model of the cracked blade is verified by comparing the modal characteristics and vibration characteristics using ANSYS software. Finally, some results show that the natural frequencies f n1 , f n2 , and f n4 increase as the pre-twisted angle and stagger angle increase. Due to the breathing effect, some integer frequencies appear in the spectrum including 0 f e and 2 f e , and the variations in the amplitude of frequencies 0 f r and 2 f r are monotonic under different aerodynamic amplitudes. The research can provide some help for the modeling of the actual blade and fault diagnosis of cracked blades. [ABSTRACT FROM AUTHOR]

An innovative experimental method, called aeroelastic real-time hybrid simulation (aeroRTHS), is proposed to study the aerodynamic vibrations of a building model in a boundary layer wind tunnel (BLWT). The aeroRTHS method aims to capture the dynamic interactions between an aeroelastic structure and the applied wind load to accurately characterize complicated, unstable phenomena such as vortex-induced vibration, and in doing so, to broaden the application of real-time hybrid simulation (RTHS) from seismic applications to wind engineering. The aeroRTHS tests were conducted in the BLWT at the University of Florida Natural Hazards Engineering Research Infrastructure Equipment Facility (UF NHERI EF). A 1-m-tall rigid physical model with an aspect ratio (height/width) of 7.3 was mounted on a modified single-axis shake table converting translational motions to corresponding rotations at the base of the model allowing the model to behave in the wind tunnel as an aeroelastic structure. A total of 128 pressure sensors located on the cross-wind sides of the physical building model measured wind pressures which then were converted to equivalent forces and ultimately resolved into a single equivalent force at the top of the physical building model based on the moment equilibrium at its base. The results from a series of aeroRTHS tests in the BLWT are reported herein to constitute a proof-of-concept study that validates the aeroRTHS method and demonstrates the aeroelastic effects on a flexible and slender structure. [ABSTRACT FROM AUTHOR]

The displacement of air masses caused by the movement of objects or vehicles is often characterized by considerable energy content, which, with appropriate technologies, can be partially recovered. In this sense, numerous scientific works consider rail transport as a possible context for application. However, the literature in the sector highlights how using existing wind technologies in these areas involves many difficulties, mainly related to the turbulent and impulsive nature of the airflows generated. This work presents the architecture and general aspects of an innovative technology for obtaining electrical energy from variable and impulsive airflows, such as those due to the rapid transit of railway trains in tunnels, without precluding its use in other similar fields. The innovative aspect mainly concerns the independent control of two distinct typologies of bladed elements, which can also have translational movement and drag-based and lift-based aerodynamic behavior to improve the adaptability of the embodiment to the site's fluid dynamic and geometric characteristics. Furthermore, the structural simplification of the apparatus, shifting some of the technological complexity to the control systems, brings further advantages in terms of construction cost, robustness, maintenance, reuse, and transferability to different contexts. Of course, the counterpart of these benefits lies in the software and hardware of the control devices. Analytical models to determine the non-dimensional performance coefficients of the two basic types have been reported as has the architectural model of the control system. The technology shown in this work is protected by an EP and US Patent. [ABSTRACT FROM AUTHOR]

This study investigated the aerodynamic behavior and structural responses of prismatic and tapered high-rise buildings under extreme wind conditions, focusing on peak wind-induced forces and moments. Using Computational Fluid Dynamics (CFD) simulations with a hybrid RANS/LES approach, the analysis explored the effects of turbulent inflow on the mean pressure coefficients, vortex dynamics, and force coefficients at different wind incidence angles (0°, 30°, and 60°). The results revealed significant differences in peak aerodynamic loads between prismatic and tapered building shapes. The tapered models experienced larger vortex formations and greater suction effects, particularly at two-thirds of the building height, with peak across-wind forces occurring at a 30° wind incidence angle. In contrast, the prismatic model showed the highest peak in along-wind forces and base overturning moments at a 60° wind incidence angle, with Karman vortex shedding and horseshoe vortices prominently captured. The study also highlighted the importance of unsteady inflow conditions in accurately predicting peak dynamic responses, particularly in the wake flow, where vortices significantly influence aerodynamic loads. [ABSTRACT FROM AUTHOR]

The utilization of unmanned sailboats as a burgeoning instrument for ocean exploration and monitoring is steadily rising. In this study, a dual sail configuration is put forth to augment the sailboats' proficiency in its wind-catching ability and adapt to the harsh environment of the sea. This proposition is based on a thorough investigation of sail aerodynamics. The symmetric rigid wing sails NACA 0020 and NACA 0016 are selected for use as the mainsail and trailing wing sail, respectively, after considering the operational environment of unmanned sailboats. The wing sail structure is modeled using SolidWorks, and computational fluid dynamics (CFD) simulations are conducted using ANSYS Fluent 2022R1 software to evaluate the aerodynamic performance of the sails. Key aerodynamic parameters, including lift, drag, lift coefficient, drag coefficient, and thrust coefficient, are obtained under different angles of attack. Furthermore, the effects of mainsail aspect ratios, mainsail taper ratios, and the positional relationship between the mainsail and trailing sail on performance are analyzed to determine the optimal structure. The thrust provided by the sail to the boat is mainly generated by the decomposition of lift, and the lift coefficient is used to measure the efficiency of an object in generating lift in the air. The proposed sail structure demonstrates a 37.1% improvement in the peak lift coefficient compared to traditional flexible sails and exhibits strong propulsion capability, indicating its potential for widespread application in the marine field. [ABSTRACT FROM AUTHOR]

The circumferential non-uniform tip clearance (CNTC) due to casing out-ofroundness adversely affects the turbine aerodynamic performance due to machining and assembly errors, thermal deformation, and improper active clearance control (ACC), etc. Moreover, the asymmetric computational domain caused by casing out-of-roundness presents difficulties for conventional numerical techniques that consider rotational periodicity. Since previous traditional methods using split computational domains have the disadvantages of high interpolation error and high time cost, an efficient fast-moving mesh (FMM) method based on an algebraic approach is proposed in this paper. This method is first validated by using a single-stage turbine with elliptical casing. The results show that the FMM has the advantages of high accuracy, high efficiency, and easy operation, which helps to solve the CNTC problem quickly in scientific research or engineering applications. Then, the effects of CNTC induced by the elliptical casing on the flow field and aerodynamic performance are investigated by using an in-house code that integrates the FMM method. Finally, the effect of stator row interference on the aerodynamic performance in the turbine stage with an elliptical casing is demonstrated. The results show that different types of elliptical casings have a significant effect on the aerodynamic performance. However, the variation law is not consistent (decreasing by 0.538% or increasing by 0.212%). Importantly, the novel finding of this paper is that this discrepancy is jointly determined by the interaction of multiple secondary flows (passage vortex, scraping vortex, etc.) at different spans, not just related to the variation of the tip leakage vortex (TLV) with tip size. Furthermore, this study is the first to indicate that the stator row interference can mitigate the extent of performance degradation due to elliptical casings by suppressing the development of secondary flows. These results may provide theoretical support for blade tip gap design and can also serve as a reasonable reference for the effective application of ACC in engineering. Finally, low-order harmonic components with high amplitudes are also innovatively found in the rotor row with a CNTC. These components may cause low-engine-order (LEO) resonances that endanger the safe operation of engines. [ABSTRACT FROM AUTHOR]

The blade profile selection is paramount for the efficient operation of straight Darrieus wind turbines in terms of torque and power generation. In this work, we have used the Kline-Fogleman Airfoil (KFA) design for the wind turbine blades. The concept of KFA design aims to cause flow separation, vortex formation, and reattachment establishment before the trailing edge. Thus, geometric tests on have been performed on the baseline airfoil NACA0015 as one of the best profiles for operating a straight Darrius wind turbine. A twodimensional Computational Fluid Dynamic (CFD) model using the twoequation Shear Stress Transport k-ω (SST k-ω) turbulent model was developed in ANSYS/FLUENT software to assess the aerodynamic efficiency of the modified airfoil. Two designs (KFA-2 and KFA-4) were tested initially in the static case. The effects of the opening step angle and its curvature diameter were studied for an angle of attack's range of -20° to +20°. The rounded KFA-4 design with an opening step angle of 93.6° led to a significant improvement in the lift-to-drag ratio thus, aerodynamic efficiency. Finally, the straight KFA-4 design with the opening step angle of 93.6° revealed a the most advantageous effects on the operation of a straight Darrieus wind turbine for a Tip Speed Ratio less than 1.6 (TSR<1.6). It allowed a noticeable reduction of the dead zone and TSR corresponding to the nominal power, thus consequently improving the starting torque and delaying torque stall. [ABSTRACT FROM AUTHOR]

This paper presents a numerical study conducted to analyze the aerodynamic performance of supersonic missiles consisting of a cylindrical body and four flat-plate rear fins arranged uniformly, equipped with conical and ogive heads. Computational Fluid Dynamics (CFD) simulations were performed using the ANSYS Fluent 17.1 solver, along with the Gambit grid generation software. The objective was to compare the aerodynamic characteristics of these two head designs in terms of drag, lift, and stability at supersonic speeds. Various flow parameters, including Mach number and angle of attack, were investigated to comprehensively assess the performance of the missile configurations. The results indicate clear differences in the aerodynamic behavior of conical and ogive heads. Specifically, there was a 2--11 percent increase in the lift coefficient of the conical heads compared to the ogive heads, and an increase in the drag coefficient of both conical and ogive heads. [ABSTRACT FROM AUTHOR]

Wind tunnel tests are costly and time-consuming, and the accuracy of the tests is limited by the size of the tunnel, to solve this problem, researchers use computational fluid dynamics (CFD) to conduct wind tunnel experiments using a computer because it is less timely and less costly. Computerized testing of drone's models using wind tunnel experiment simulation in computational fluid dynamic (CFD) software requires knowledge of the most suitable turbulence model for this drone. In this paper ANSYS fluent program has been used to test four most common turbulence models for use (Spalart-Allmaras, K-Epsilon, K-Omega and Reynolds stress) and laminar flow on the ScanEagle drone model (an aerial reconnaissance drone used in military and intelligence operations) and calculated their effect on aerodynamic parameters In terms of accuracy and time to solution, concluded that the best turbulence model in terms of balancing accuracy and the time taken for the calculation is K-Omega model. [ABSTRACT FROM AUTHOR]

This study proposes the use of light detection and ranging (LiDAR) remote sensing (RS) to support morphometric research for estimating the aerodynamic roughness length ( z 0 ) of building placement on various scales. A LiDAR three-dimensional point cloud (3DPC) data processing graphical user interface (GUI) was developed to explore the z 0 and related urban canopy parameters (UCPs) in the Incheon metropolitan area in South Korea. The results show that multi-scale urban aerodynamic roughness exploration is viable and can address differences in urban building data at various spatial resolutions. Although validating morphological multi-scale UCPs using dense tall towers is challenging, emerging low-cost and efficient methods can serve as substitutes. However, further efforts are required to link the measured z 0 to building form regulations, such as floor area ratio, and expand RS research to obtain more quantitative and qualitative knowledge. [ABSTRACT FROM AUTHOR]

Currently, considerable attention is being directed toward active debris removal (ADR) using small, cost-effective satellites. From high altitude to re-entry, ADR missions use thrusters that consume significant amounts of fuel. The volume of the propulsion system in these satellites can be quite large, and it is difficult for a small satellite to accommodate a large-scale propulsion system. Thus, active utilization of atmospheric drag is being considered for small satellites with low capability. However, the principal challenge for small satellites to remove large debris is to deal with the large disturbance torque caused by strong atmospheric drag on the debris. This paper proposes attitude guidance around an equilibrium (balance) point in attitude dynamics acted on by gravity gradient and aerodynamic torques. The desired attitude is set to optimize two conflicting objectives: maximizing the projection area to generate large aerodynamic force and minimizing the disturbance torque. In this paper, we develop an aerodynamic database (ADDB) by rigorously calculating the aerodynamic torque for each altitude and solar array paddle (SAP) rotation based on an aerodynamic characteristic model of free molecular flow. Using the ADDB, the SAP angle and orbit altitude effects on the torque equilibrium attitude (TEA) are clarified. Then, the mean disturbance torque map at each orbit altitude is introduced to obtain the candidate TEA paths. The effectiveness of the proposed paths for debris descent is demonstrated through numerical simulations. • Active debris removal mission by small satellites was considered. • Aerodynamic database was developed using an aerodynamic characteristic model. • The effect of SAP angle on aerodynamic moment was evaluated. • Candidate TEA paths were obtained from the proposed torque disturbance maps. • The optimal path was designed considering both duration and amount of torque. [ABSTRACT FROM AUTHOR]

Drones are becoming indispensable in emergency search and rescue (SAR), particularly in intricate urban areas where rapid and accurate response is crucial. This study addresses the pressing need for enhancing drone navigation in such complex, dynamic urban environments, where obstacles like building layouts and varying wind conditions create unique challenges. Particularly, the need for adapting drone autonomous navigation in correspondence with dynamic wind conditions in urban settings is emphasized because it is important for drones to avoid loss of control or crashes during SAR. This paper introduces a pioneering method integrating multiobjective reinforcement learning (MORL) with a convolutional autoencoder to train autonomous drones in comprehending and reacting to aerodynamic features in urban SAR. MORL enables the drone to optimize multiple goals, whereas the convolutional autoencoder generates synthetic wind simulations with a substantially lower computation cost compared to traditional computational fluid dynamics (CFD) simulations. A unique data transfer structure is also proposed, which fosters a seamless integration of perception and decision-making between machine learning (ML) and reinforcement learning (RL) components. This approach uses imagery data, specific to building layouts, allowing the drone to autonomously formulate policies, prioritize navigation decisions, optimize paths, and mitigate the impact of wind, all while negating the necessity for conventional aerodynamic force sensors. The method was validated with a model of New York City, offering substantial implications for enhancing automation algorithms in urban SAR. This innovation enables the possibility of more efficient, precise, and timely drone SAR operations within intricate urban landscapes. [ABSTRACT FROM AUTHOR]

The tall building design process typically goes through a time-consuming iterative procedure to ensure the cost efficiency of the proposed structural system, especially in the conceptual design stage where the layout is designed. Despite that, this procedure does not guarantee to yield an optimal layout. Consequently, an automated layout optimization procedure will result in a more economical and sustainable design. This paper presents a novel multiobjective lateral load resisting system (LLRS) (i.e., shear walls) layout optimization framework provided for dynamically sensitive tall buildings subjected to a wind load time history. The developed framework relies on an artificial neural network (ANN) surrogate model for constraints and objective function evaluation to reduce the computational time of the optimization process. The adopted surrogate model is built based on an automated finite element models-generated database using MATLAB code via the Open Application Program Interface of the ETABS software. The ANN surrogate model proved its efficiency in capturing complex variations in the structural response with a correlation coefficient that ranges between 90% and 98%. A nongradient optimization algorithm (NSGA-II) is adopted to identify the optimal shear wall layout to resist the applied dynamic wind load. In order to reduce the number of optimal layout solutions on the Pareto front, a pruning algorithm is used to limit the optimal solutions to 24 layouts. This will enable designers to use the direct selection method to choose an appropriate layout that fits the project's objectives. Also, a case study building is presented where the optimized results are analyzed and discussed in the numerical example to verify the effectiveness of the proposed optimization framework. [ABSTRACT FROM AUTHOR]

In urban settings, buildings create complex turbulent conditions, affecting helicopter flight performance during missions and increasing safety risks during takeoff and landing. A numerical study on rotor–building coupled flow field is carried out to address rotor aerodynamic performance under building interferences in natural atmospheric conditions. A high-fidelity atmospheric boundary layer (ABL) model described by an exponential law is established herein. The solution of the coupled flow field is based on the Reynolds-averaged Navier–Stokes (RANS) equations, with the rotor's rotation achieved through the overset grid method. Based on the dominant wind features, the building flow field is distributed into four regions, where the updraft along the headwind side impacts the rotor, bringing about a 76% increase in pitching moment. On the lateral side of the building, distorted rotor wake squeezed upward into the rotor disk, leading to severe blade–vortex interaction (BVI). During low-altitude hovering over rooftops, the mixing of building shed vortices with forward flow wakes causes the formation of a circulation region on the rotor's windward side, resulting in a thrust loss of approximately 7.8%. Meanwhile, the flow environment on the leeward side of the buildings is more stable. Therefore, it is recommended that helicopters adopt a headwind approach during rooftop operations. However, an 11.4% loss in the average hover figure of merit is observed due to consistent thrust losses caused by the recirculation region. [ABSTRACT FROM AUTHOR]

A long-span double-deck steel truss suspension bridge is easy to produce vortex-induced vibration (VIV) at low air velocity, which affects bridge service life. Additional aerodynamic measures play a role in suppressing VIV by changing the aerodynamic shape, which is a common control method. As the main aerodynamic measure to suppress the VIV response, wind fairing is widely used in engineering practice. In order to obtain the optimal additional position and shape parameters of the fairing, Huangjuetuo Yangtze River Bridge is the research target. Through the combination of a wind tunnel test and numerical simulation, the VIV response of the original and fairing section is studied. Based on data analysis, it is revealed that these additional fairings to the upper chord can significantly reduce the VIV response. When the shape parameters of the fairing are h/D = 1/4 and l/D = 1, the VIV inhibition efficiency is the highest, which can reach 65.51%. By analyzing the flow distribution, it can be seen that VIV is caused mainly by vortex separation in the upper bridge board area. Although this wind fairing does not change the original vortex shedding forms, it changes the first separation point and movement direction of the airflow, making the vortex scale generated by the airflow smaller and the vorticity lower, thus effectively suppressing VIV. [ABSTRACT FROM AUTHOR]

Air-permeable multilayer cladding (vinyl siding, roof pavers, discontinuous metal roofing, solar panels, etc.) are one of the most common types of building components in North America. Their defining aerodynamic feature is that they have an air cavity separating the component from the sheathing, studs, or interior layer. Due to air-permeability, external wind loads can transfer into the air cavity between the layers. Although these cladding systems have similar geometries in many ways, design loads are not generally available for such systems. This study aims to synthesize the available literature on the pressure equalization factor, which is the proportion of external load acting on the cladding and provide a framework for design wind loads on air-permeable multilayer cladding systems. To accomplish this, the many factors that affect the pressure equalization factor, such as the gap-to-cavity-depth ratio, panel size, and exposure are discussed. Then, the pressure equalization factors from multiple studies are combined to examine the effect of effective area on the pressure equalization factor. Finally, recommendations for implementing these guidelines into design standards are provided. [ABSTRACT FROM AUTHOR]

Buildings increase the urban surface roughness and reduce near‐surface wind speeds in the urban canopy due to the drag effect. Urban heat storage and other effects cause urban warming as well, which decreases the urban boundary layer stability and enhances the turbulence exchange between upper and lower layer. As upper momentum is transported downward, the wind speed of urban canopy increases. Quantitative descriptions of these mechanisms are still lacking currently. This paper presents high‐resolution numerical simulation results of a mega city, Shanghai, China from 2016 to 2020 using the building effect parameterization in WRF (WRF‐BEP) with urban morphological parameters. The dynamic and thermal effects of building morphology on urban canopy wind speed were separated and their quantitative expression functions were given. The results indicate that the influence of building morphology on urban canopy wind speed is mainly dynamic resulting in a wind speed attenuation of approximately 50% and nearly constant. The thermal effect of building morphology on urban canopy wind speed increases with the urban heat island intensity, and the thermal effect could increase urban canopy wind speed by about 30% under the condition of strong urban heat island. The relative contributions of the dynamic and thermal effects of building morphology to urban canopy wind speed change with the wind speed. As wind speed increases, the contribution of the thermal effect of building morphology to urban canopy wind speed gradually decreases. This paper provides a quantitative relationship between the urban canopy wind speed variation and urban morphology, as well as urban heat island intensity. Plain Language Summary: Urbanization changes the dynamic and thermal properties of urban and creates new dynamic and thermal processes in urban areas. Buildings increase the urban surface roughness and reduce urban canopy wind speed due to the drag effect. At the same time, urban warming causes the downward transportation of momentum, which increases the wind speed. Quantitative descriptions of these mechanisms are lacking currently. This study investigated the impact of building morphology on urban canopy wind speed using WRF‐BEP model with high‐resolution urban morphological parameters. The dynamic and thermal effects of building morphology on urban canopy wind speed were separated and their quantitative expression functions were given. Key Points: The dynamic and thermal effects of building morphology on urban canopy wind speed are separatedThe quantitative expression functions of the dynamic and thermal effects of building morphology on wind speed are givenThe relative contributions of the dynamic and thermal effects on urban canopy wind speed are investigated [ABSTRACT FROM AUTHOR]

CFD offers advantages over wind tunnel experiments in the prediction and optimization of building wind environment; however, the computational costs associated with optimizing architectural wind environment remain a challenge. In this study, an approach that combines deep learning techniques with CFD simulations is proposed for the prediction and optimization of the architectural wind environment efficiently. A dataset of wind field is constructed using CFD simulation, considering various wind directions, wind speeds, and building spacing. Subsequently, a U-net deep learning model is trained as a surrogate model to rapidly predict the architectural wind field under different conditions. The results indicate that the model can accurately predict the wind field in buildings. The prediction time of building wind field is only 1/900 of that of CFD simulations, making it a viable surrogate model for wind environment optimization. Furthermore, considering all the building layouts and inflow conditions examined in this study, the maximum and minimum uniform wind speed area ratios Auni are 0.84 and 0.13, respectively. Under a single inflow speed, the maximum improvement in the Auni is 0.4, with an improvement rate of 48%. The results demonstrate the effectiveness of the proposed method as an efficient approach for optimizing architectural wind environment. [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]

Mitigating tornado damage remains a critical challenge for communities throughout much of the United States. Enhanced construction techniques typically used in hurricane-prone regions are often recommended as at least part of the solution, but the effectiveness of these techniques lacks empirical evaluation. This study investigates the performance of modern wood-frame residential structures in Arabi, LA, constructed to hurricane-resistant standards, that were impacted by a strong tornado on March 22, 2022. Field teams deployed beginning March 25, 2022, just three days after the tornado touched down, capturing perishable data on the building performance using vehicle-mounted surface-level panoramic cameras, forensic engineering investigations, and unmanned aerial systems. This paper describes the field deployments and identifies common failure mechanisms observed by the field teams. Analytical fragility functions are developed based on the load path observations and compared to empirical fragility functions generated from linking the building performance observations with wind speed estimates at each building derived from a parametric wind field model conditioned to tree-fall patterns. The study finds that despite the frequent use of hurricane-resistant hardware, such as hurricane straps and anchor bolts, key weak links elsewhere in the load path compromised the resistance and led to premature failures. The agreement between the empirically- and analytically-derived fragility functions was lacking, demonstrating the challenges that remain in understanding near-surface tornado wind loading and structural response. Nonetheless, the study provides a consensus framework for future tornado assessments that can help improve our understanding of tornado loading through the utilization of reconnaissance data. Further, the study findings on deficiencies in the load paths of homes in hurricane-prone regions have practical value to risk assessments and future construction practices. [ABSTRACT FROM AUTHOR]

Background and Aims Is the increase in species diversity patterns towards lower latitudes linked to reproductive traits? Plant reproductive organs influence reproductive isolation and hence species divergence. Abiotic differences between temperate and tropical regions can also directly impact on plant reproductive traits. Here we provide a novel overview of southern hemisphere, Afromontane forest tree taxonomical patterns and ask whether reproductive traits relate to latitude, while accounting for environmental (tree height) and evolutionary (biogeographical affinity) selective forces. Methods We compiled a novel dataset with (1) flower colour, size and pollination syndrome and (2) fruit colour, size and dispersal syndrome for 331 tree species found in six Afromontane forest regions. We categorized each species into latitudinal distribution using these six regions, spanning the southern Cape (34º S) to Mount Kenya (0º S). Additionally, we gathered maximum tree height (m) for each species and determined the global distribution of all 196 tree genera (Afrotropical, Palaeotropical or Pantropical). Key Results Species, genera and families showed a general decrease in richness away from tropical and subtropical forests towards warm temperate forests. Southern Afrotemperate forests (the furthest south) had the highest tree endemism. There was no relationship between latitude and the reproductive traits tested here. Biogeographical affinity related to fruit colour and dispersal syndrome, with palaeotropical genera showing relative increases in black-purple fruit colour compared with pantropical genera, and palaeotropical genera showing relative increases in biotic seed dispersal compared with Afrotropical genera, which showed higher relative abiotic seed dispersal. Taller trees had a higher chance to be wind or insect pollinated (compared with bird pollinated) and had larger fruits. Conclusions Latitude explained patterns in Afromontane tree taxonomic diversity; however, tree reproductive traits did not relate to latitude. We suggest that phylogenetic conservatism or convergence, or both, explain the reported patterns. [ABSTRACT FROM AUTHOR]

Comprehensive rotorcraft simulation codes are the workhorses for designing and simulating helicopters and their rotors under steady and unsteady operating conditions. These codes are also used to predict helicopters' limits as they approach rotor stall conditions. This paper focuses on the prediction of maximum rotor thrust when hovering (due to stall limits) and the thrust and power characteristics when the collective control angle is further increased. The aerodynamic factors that may significantly affect the results are as follows: steady vs. unsteady aerodynamics, steady vs. dynamic stall, blade tip losses, curvature flow, yaw angle, inflow model, and blade-vortex interaction. The inflow model and tip losses are found to be the most important factors. For real-world applications vortex-based inflow models are considered the best choice, as they reflect the blade circulation distribution within the inflow distribution. Because the focus is on the impact of aerodynamic modeling on rotor stall, the blade design and its flexibility are intentionally not considered. [ABSTRACT FROM AUTHOR]

Aircraft propellers produce relatively large in-plane loads, called propeller 1P loads, during maneuvers such as turning, diving, and lifting, and these loads can negatively affect the flight and control of the aircraft. In order to study the change rule of 1P aerodynamic loads, in this paper, a mathematical model of the propeller 1P aerodynamic loads has been developed based on the blade element momentum theory. This mathematical model was then corrected using the Pitt–Peters incoming flow correction method, the Prandtl tip correction method, and the propeller root flow correction method. Based on this mathematical model, a calculation procedure for the propeller 1P aerodynamic loads was developed using MATLAB software, and the accuracy of the procedure was verified by comparing the results with CFD simulation results. Numerical simulations show that the results calculated based on the proposed mathematical model for the coefficients of thrust, power, bending moment, and the tangential force of the propeller have an error of less than ±6.00% compared to the CFD simulation results. For a small inflow angle, the coefficients of bending moment and tangential force of the whole propeller fluctuate in a small range. But, as the inflow angle increases, the fluctuation range of the aerodynamic characteristic parameters of the propeller increases and the fluctuation becomes more complicated. Through numerical calculations, it has been shown that the mathematical model presented herein is reliable and accurate. In addition, it greatly shortens the calculation time and improves the calculation efficiency. It is expected that the proposed model can provide a certain help for the strength design of the propeller structure and the study of the aerodynamic performance of the whole aircraft. [ABSTRACT FROM AUTHOR]

In China's mountainous coastal terrain, storms can badly damage low-rise buildings. At present, it is not clear how the relative position of buildings and mountains affects the surface of low-rise buildings. The study compared these results with the wind pressure distribution without the surrounding environment. The distribution of wind pressure in different hillside landforms is examined through a wind tunnel experiment, which is also compared with the distribution in an open environment. The study examined the fluctuating coefficient as the distance between the building and the hillside changed, specifically for wind blowing at a 0° angle. The investigation examined the power spectrum and wind pressure probability distribution while considering the proximity of the building to an adjacent hill. The findings indicated that as the distance between the slope and the mountain increases, the fluctuating wind pressure coefficient continues to increase, and the contour lines of the wind pressure distribution are relatively denser compared to where there is a mountain. The maximum value of the fluctuating wind pressure coefficient is 0.22, which appears at the windward roof. The roof's wind pressure coefficient fluctuated and gradually increased until it reached its peak, unaffected by the surroundings. The wind pressure on the leeward side exhibited Gaussian characteristics in its probability distribution. [ABSTRACT FROM AUTHOR]

Based on the numerical-simulation test data from the wind tunnel, the wind-pressure characteristics of low-rise buildings with gable roofs are examined and compared to standard values under different roof slopes, eave heights and terrains. To further investigate the underlying mechanisms of variation, a numerical-simulation study was conducted for selected conditions. The results indicate that when the roof slope is less than 3:12, the negative value of the shape coefficient for the windward roof of the building can reach up to -0.89, far exceeding the code value of -0.5. It is suggested that when the slope is not larger than 3:12, the shape coefficient for the windward roof should be -0.9 and the coefficient for the leeward roof should be determined through linear interpolation within the range from -0.4 to -0.75 based on the roof's slope size. With the increase of eave height and the decrease of ground roughness, the vortex intensity of the roof and the leeward surface increases and the area proportion of high negative pressure area in the vortex influence range increases. Thus, the negative value of the shape coefficient for the roof and the leeward surface becomes larger, which is higher than the code value. It is proposed that under an eave height of 12 m, the shape coefficient for the windward roof should be -0.95. Meanwhile, those of the leeward roof, leeward surface and sidewall 2 should be -0.6 under open terrain. [ABSTRACT FROM AUTHOR]

Composite corrugated plates have a great potential in the application to morphing wings. However, it takes high computational cost to conduct flutter analysis with detailed 3D finite element models due to its structural complexity. In this study, an analytical method is proposed for flutter stability analysis of composite corrugated plates in supersonic flow. The trapezoidal and sinusoidal composite corrugated plate is homogenized as an equivalent anisotropic plate based on an energy approach. The flutter model for the composite corrugated plate is derived based on Kirchhoff plate theory and the equivalent stiffness properties. The unsteady aerodynamic pressure is evaluated by using the supersonic piston theory in which the corrugated section is taken into account. Hamilton's principle with the assumed mode method is applied to formulate the aeroelastic equation of the composite corrugated plate. The eigenvalue criterion is utilized to reveal the flutter mechanism and evaluate the stability of composite corrugated plates in supersonic flow. The accuracy and reliability of the present method are verified by comparing aeroelastic responses with those obtained from commercial software. Parametric studies concerning different parametric variables are also conducted. It is shown that the proposed method has sufficient accuracy and requires less computational effort, providing a theoretical basis for the utilization of trapezoidal and sinusoidal composite corrugated plates in morphing wings. [ABSTRACT FROM AUTHOR]

A closed-loop control framework is developed for the co-flow jet (CFJ) airfoil by combining the numerical flow field environment of a CFJ0012 airfoil with a deep reinforcement learning (DRL) module called tensorforce integrated in Python. The DRL agent, which is trained through interacting with the numerical flow field environment, is capable of acquiring a policy that instructs the mass flow rate of the CFJ to make the stalled airfoil at an angle of attack (AoA) of 18 degrees reach a specific high lift coefficient set to 2.0, thereby effectively suppressing flow separation on the upper surface of the airfoil. The subsequent test shows that the policy can be implemented to find a precise jet momentum coefficient of 0.049 to make the lift coefficient of the CFJ0012 airfoil reach 2.01 with a negligible error of 0.5%. Moreover, to evaluate the generalization ability of the policy trained at an AoA of 18 degrees, two additional tests are conducted at AoAs of 16 and 20 degrees. The results show that, although using the policy gained under another AoA cannot help the lift coefficient of the airfoil reach a set target of 2 accurately, the errors are acceptable with less than 5.5%, which means the policy trained under an AoA of 18 degrees can also be applied to other AoAs to some extent. This work is helpful for the practical application of CFJ technology, as the closed-loop control framework ensures good aerodynamic performance of the CFJ airfoil, even in complex and changeable flight conditions. [ABSTRACT FROM AUTHOR]

This paper devises a new method for estimating the maximum response and maximum control force for high-rise base-isolated buildings with active structural control (active base isolation) to simplify the conventional complex design procedure. While active base isolation has emerged as a prominent solution for achieving high control performance, its design process is inherently complex, particularly when applied to high-rise buildings where wind loads become prominent. To address this problem, we propose a streamlined method inspired by the gust factor methodology widely used in conventional passive wind-resistant designs. This method estimates the maximum response and maximum control force without the need for numerical simulations. We first construct an equivalent passive model of a multi-degree-of-freedom control system to theoretically compute the dynamics of the system. Based on the constructed equivalent passive model and then propose a method to calculate the mean displacement and mean control force using only the static equilibrium of this model. Furthermore, we extend the conventional gust factor approach to active base isolation to estimate the maximum displacement and maximum control force for active base isolation without the need for numerical simulations. We validate our methods through a series of numerical examples, incorporating key parameters such as feedback gain, aspect ratio of building, return period of wind force, and stiffness of isolation. Numerical verifications show that the mean response and mean control force are estimated by the static equilibrium of the proposed equivalent passive model. Moreover, the maximum response and maximum control force can be estimated by the proposed gust factors. Our methods can be applied for feedback control systems using a given feedback gain. [ABSTRACT FROM AUTHOR]

Due to the complex aerodynamic effects, the reentry trajectory optimization problem is highly nonlinear. When using sequential convex programming (SCP) methods to solve it, the iteration solution is difficult to converge. To improve this, we propose a hybrid-order soft trust region-based SCP method. We analyze the penalty effect of typical trust regions. Based on the analysis, we develop a hybrid-order soft trust region combining a small-weight first-order component and a higher-order components. To solve the subproblem reliably and effectively, we equivalently reformulate it as a second-order cone programming (SOCP) form through the relaxation technique. Combined with the line search method, we further design an SCP algorithm with guaranteed convergence under some assumptions. In the numerical simulations, the effectiveness and robustness of the proposed method have been verified using a nominal case and 200 Monte Carlo cases. [ABSTRACT FROM AUTHOR]

Online identification of aerodynamic parameters of experimental rockets was completed based on unscented Kalman filtering (UKF). Numerical simulation, hardware-in-the-loop (HIL) simulation, and flight tests were conducted. The identification error of aerodynamic force in numerical simulation and HIL simulation is within 2%. For flight test data, trajectory reconstruction was performed using the identified aerodynamic forces, and the results showed that the identification results were more accurate than the interpolation table calculation results. The flight test identification results show that the identification method can complete parameter online identification under the conditions of limited performance of onboard computers, real sensor errors, and servo response. The approximate linear correlation between α and δ e and the reason for their formation from the moment balance were analyzed. It was pointed out that when the recognition sampling period is long, this phenomenon will affect the identification of parameters, and a solution is proposed. [ABSTRACT FROM AUTHOR]

The next-generation variable cycle engine imposes stricter requirements on a fan's flow capacity at the middle speed. To tackle this challenge, the implementation of split fans presents as a potential solution. In the present study, we conducted numerical simulations using the commercial software NUMECA to investigate the aerodynamic performance variation with bypass ratios for variable cycle split fans in "1 + 2" and "2 + 1" configurations at 80% rpm. The results indicate that the flow capacity of the split fans exhibits an increasing trend with a rise in the bypass ratio at 80% rpm and subsequently stabilizes upon reaching a certain bypass ratio. Specifically, the flow capacity of the "2 + 1" split fans is particularly stronger at the small bypass ratios, whereas the "1 + 2" split fans exhibit superior maximum flow capacity at the high bypass ratios. Additionally, there is a significantly faster increase in the flow capacity of the "1 + 2" split fans compared to that of the "2 + 1" split fans. Furthermore, when the flow capacity of the split fans reaches its maximum, both the efficiency and stall margin achieve their optimal values, indicating that the corresponding bypass ratio is optimal. [ABSTRACT FROM AUTHOR]

Traditional aerodynamic modeling methods have some difficulties in multiparameter unsteady state-space modeling and control law design, which raise significant challenges in flight control. The rapid development of machine learning provides a new idea for unsteady aerodynamic modeling and control law design, which has significant value for theoretical research and engineering application. In this paper, an unsteady aerodynamic model environment was established based on deep neural network (DNN), and a dynamic computational fluid dynamics (CFD) virtual environment was taken as an approximation of the real environment. A deep reinforcement learning (DRL) longitudinal-axis flight control method was studied on the basis of both environments. The deep deterministic policy gradient (DDPG) algorithm was used to implement flight control, and the effects of different constraints in the reward function on the results of DRL were studied at the same time. The results show that the DDPG agent effectively achieves longitudinal-axis flight control in the model environment. The DDPG agent trained in the model environment was also used for longitudinal-axis flight control in the dynamic CFD virtual environment, and this method provides a reference for the coupling of dynamic CFD and DRL. The control results from the model environment and the dynamic CFD virtual environment are compared, and results show that the DDPG agent has good robustness in both environments. The results of this study suggest that machine learning and deep reinforcement learning can effectively solve complicated multiconstraint, uncertain, and sophisticated control tasks. In this paper, a DNN-based unsteady aerodynamic modeling method was established based on dynamic computational fluid dynamics calculation and machine learning, and the results show that the DNN-based unsteady aerodynamic model has advantages in dealing with highly nonlinear data under unsteady conditions. In addition, the deep deterministic policy gradient algorithm can be well applied in longitudinal-axis flight control, and the agent can be trained in DNN-based unsteady aerodynamic model environment. The agent was also used for longitudinal-axis flight control in the dynamic computational fluid dynamics virtual environment, and the results show that the agent has good robustness in both environments. This provides the possibility for the agent to achieve longitudinal-axis flight control in a real environment. [ABSTRACT FROM AUTHOR]

Highlights: What are the main findings? Model of strong wind flow around sharp edges; Analysis of the impact of strong wind on structures. What is the implication of the main findings? Theoretical and numerical analysis; Observations and measurements of impacts on existing facilities; Comparison of results depending on the solutions used. The aim of this research is to analyze the pressure distribution caused by wind pressure on the structure of a single-family house. The research object is a model reflecting a real structure, which was damaged in 2018 because of heavy winds. The main idea is to create numerical models using various complex structural analysis software and compare the results. The obtained results will be compared with each other to analyze the impact of various factors, hereinafter referred to as boundary conditions, on the pressure values in characteristic places of the facility. The values closest to the normal distribution will be compared to the actual damage to the house structure. The essence of the research will be the identification of phenomena occurring during the action of heavy winds in global conditions (European and American), considering modifications and different ways of creating seemingly similar numerical models and the way they work. Everything will be compared with each other to find the most optimal design method in the given programs and to obtain wind pressure results that are closest to the real ones. [ABSTRACT FROM AUTHOR]

Airflow over a square cross-section at high Reynolds numbers and different angles of incidence is investigated with the aim of providing deeper insight into wind actions on elongated structures and, in particular, tall buildings. The flow around bluff bodies is characterized by separation at sharp corners, as well as possible flow reattachment at side surfaces. The alternate shedding of vortices is also generated in the wake of bluff bodies due to the unsteady nature of flow separation. Two-dimensional (2D) URANS numerical simulations were conducted in order to model transient flow and examine wind actions on a square used as a model of a typical cross-section of a tall building far from its roof and the ground. For validation purposes, the study's numerical results on drag and lift coefficients, Strouhal numbers, as well as pressure coefficient distribution were found to be in good agreement with available experimental and numerical results in the literature for relatively low Reynolds numbers. The numerical study was then extended to higher Reynolds numbers, approaching values that are pertinent for wind flow around buildings, thus addressing the lack of such results in the literature. On the basis of these results, the impact of Reynolds numbers and angles of incidence on drag and lift coefficients, as well as the pressure coefficient distribution along the walls of the cross-section, is highlighted. [ABSTRACT FROM AUTHOR]

The escalating global demand for electricity is driving a significant expansion in the size and complexity of electric power systems. Explosive growth strains power distribution, creating challenges for operators. Among these challenges, the imperative to minimise power losses is crucial. To enhance power efficiency and quality, Distributed Generation (DG) technology, particularly wind energy, is being integrated into distribution systems. However, the variable nature of wind speed poses a significant challenge to the seamless integration of wind energy into grids. To address this challenge, wind speed prediction methods are explored. In this work, a Machine Learning framework is employed for multivariate wind speed forecasting in Tamil Nadu, India $\left[{{{8.0883}^ \circ }N,{{77.5385}^ \circ }E} \right]$ 8.0883 ∘ N , 77.5385 ∘ E . Key performance metrics, such as Root Mean Square Error (RMSE) and Mean Absolute Percentage Error values (MAPE), are used to assess the accuracy of the wind speed predictions. The predicted wind speed data is then utilised to estimate wind farm power output which is seamlessly integrated into the distribution system. Load Flow analysis is conducted using the robust and straightforward current injection method, focusing on IEEE-33 and IEEE-69 bus-balanced Mesh distribution systems. The aim is to determine the impact of wind-powered Distributed Generation on power losses within these systems. [ABSTRACT FROM AUTHOR]

The aerodynamic noise of an open rotor is one of the critical challenges that must be considered in its design and application. FODNOPP, a program specifically programmed to predict the aerodynamic discrete noise of single- and counter-rotating open rotors (such as propellers, propfans, and rotorcraft rotors) at subsonic, transonic, and supersonic helical blade tip speeds, has recently been developed by the first author. This program is composed of four prediction codes, namely code a1, code a2, code b, and code c, each based on Farassat-derived formulations Formu 1-RTE, Formu 1A, Formu 1-Sph, and Formu 3, providing time-domain solutions to the Ffowcs Williams–Hawkings equation. Four verification examples for both propeller low-speed flight noise and counter-rotating propfan take-off noise are presented, along with an application case for transonic helical tip speed counter-rotating propfan cruise noise. The results demonstrate the accuracy of FODNOPP in calculating the noise for these verification cases. And in the counter-rotating propfan cruise noise case, the maximum harmonic sound pressure level of the rear propfan is 5.5 dB higher than that of the front propfan. FODNOPP can be referred to as a comprehensive design tool, and it offers valuable guidance for engineering design focused on rotor-related noise reduction. [ABSTRACT FROM AUTHOR]

The request for faster and greener civil aviation is urging the worldwide scientific community and aerospace industry to develop a new generation of supersonic aircraft, which are expected to be environmentally sustainable and to guarantee a high-level protection of citizens. A key aspect to monitor the potential environmental impact of new configurations is the aerodynamic efficiency and its impact onto the real mission. To pursue this goal, this paper discloses increasing-fidelity aerodynamic modeling approaches to improve the conceptual design of high-speed vehicles. The disclosed methodology foresees the development of aerodynamic aerodatabases by means of incremental steps starting from simplified methods (panels methods and/or low-fidelity CFD simulations) up to very reliable data based on high-fidelity CFD simulations and experimental measurements with associated confidence levels. This multifidelity approach enables the possibility of supporting the aircraft design process at different stages of its design cycle, from the estimation of preliminary aerodynamic coefficients at the beginning of the conceptual design, up to the development of tailored aerodatabases at advanced design phases. For each design stage, a build-up approach is adopted, starting from the investigation of the clean external configuration up to the complete one, including control surfaces' effects and, if any, the effects of the integration of the propulsive effects. In addition, the applicability of the approach is guaranteed for a wide range of supersonic and hypersonic aircraft, and the developed methodology is here applied to the characterization of Mach 2 aircraft configuration, a relevant case study of the H2020 MORE&LESS project. [ABSTRACT FROM AUTHOR]

Aircraft designers are mainly interested in finding the level of pressure, stresses, and deformations of the parts of the aircraft wing. In many aviation accidents, the failure of the wing is the main cause of disasters, as it is considered the main surface that generates the necessary lift for the aircraft in addition to its other functions in controlling the transverse stability. In this work, a numerical study was performed to obtain the optimum wing structural design parameters for high strength and minimum weight for the L-39 A/C wing. The wing was modeled as a honeycomb with different thicknesses using the software SOLIDWORKS 2020. The pressure distribution was predicted using the FLUENT 2022 R1 package. Having obtained the aerodynamic pressure, the deformations and stresses were obtained using the ANSYS program. The results were compared with other researchers using other models, such as using ribs and stringers in the interior structure of the wing. The current results were found to be reliable and acceptable from the design point of view of the high stiffness-to-weight ratio. [ABSTRACT FROM AUTHOR]

For this paper, full-scale/model test comparisons to validate the traditional atmospheric boundary layer (ABL) wind-tunnel simulation technique performed until now by the wind engineering community are systematically reviewed. The engineering background includes some benchmark low-rise buildings specifically established for use in wind engineering research (the Aylesbury experimental buildings, the Texas Tech University experimental building, the Silsoe buildings, etc.), several high-rise buildings in North America and East Asia, long-span bridges, large-span structures, and cooling towers. These structures are of different geometries, are located in different wind environments, and are equipped with various transducers and anemometers. By summarizing the different articles in the literature, it is evident that notable discrepancies between the full-scale measurement and the model test results were observed in most full-scale/model test comparisons, which usually took certain forms: the mean and/or the peak negative pressures at the flow separation regions on buildings were underestimated in the wind tunnel; differences in the root-mean-square (rms) values of the acceleration samples between the full-scale measurements and the force balance model tests were non-negligible; the vertical vortex-induced vibration amplitudes of bridges measured using section models and aero-elastic models were much lower than those observed on the prototypes, etc. Most scholars subjectively inferred that inherent technical issues with the ABL wind tunnel simulation technique could be responsible for the observed full-scale/model test discrepancies, including the Reynolds number effects, the turbulent flow characteristics effects, and the non-stationarity effects. However, based on the authors' years of experience and after discussion with experienced researchers, it was found that some of the full-scale measurements performed in earlier research were inherently less accurate and deterministic than the wind tunnel experiments they were supposed to validate, which could also be a significant cause of the full-scale/model test discrepancies observed. It is suggested herein that future studies in this field should regard full-scale measurements only as benchmarks, and that future works should focus on synthesizing the results from different schools of physical experiments and formulating universal empirical models of high theoretical significance to properly validate future wind tunnel tests. [ABSTRACT FROM AUTHOR]

The CO2 storage (Fs) is the cumulation or depletion in CO2 amount over a period in an ecosystem. Along with the eddy-covariance flux and wind-stream advection of CO2, it is a major term in the net ecosystem CO2 exchange (NEE) equation and even dominates in the equation under a stable atmospheric stratification while this equation is used for forest ecosystems over complex terrains. However, estimating the Fs remains challenging due to the frequent gusts and random fluctuations in boundary-layer flows that arouse tremendous difficulties in catching the true trend of CO2 changes for its storage estimation from eddy-covariance along with the atmospheric profile techniques. Using the measurements from Qingyuan Ker Towers equipped with NEE instrument systems separately covering mixed-broadleaf, oak, and larch forests towers in a mountain watershed, this study investigates the gust periods and CO2 fluctuation magnitudes while examining their impact on Fs estimation in relation to the terrain complexity index (TCI). The gusts induce CO2 fluctuations at numerous periods of 1 to 10 min over two hours. Diurnal, seasonal, and spatial differences (P < 0.01) in the maximum amplitude of CO2 fluctuations (Amax) ranges from 1.6 to 136.7 ppm and these difference in a period (Pmax) at the same significant level ranges 140 to 170 second. The Amax and Pmax are significantly correlated to the magnitude and random error of Fs with diurnal and seasonal differences. These correlations decrease as CO2 averaging time windows becomes longer. To minimize the uncertainties of Fs, a constant [CO2] averaging time window for the Fs estimates is not ideal. Dynamic averaging time windows and a decision-level fusion model can reduce the potential underestimation of Fs by 29%-33%, 37 being equivalent to 1.9%-4.3% underestimation of the NEE for temperate forests in complex terrains. The relative contribution of Fs to the 30-min NEE observations ranged from 17% to 82% depending on wind speed and TCI. The study's approach is notable as it incorporates TCI and utilizes three flux towers for replication, making the findings relevant to similar regions with a single tower. [ABSTRACT FROM AUTHOR]

The Mars rotorcraft is an aerial exploration platform capable of repeated take-offs and landings to extend the range of rover explorations. NASA's Ingenuity helicopter is a full y functioning coaxial helicopter for technology demonstration. Increasing the rotor diameter or the number of blades can enhance the load capacity of the coaxial helicopter but would make it difficult to be folded. A more suitable configuration for Mars exploration is the multi-rotor aircraft, which has a stronger load capacity with the same rotor diameter. Although the aerodynamic performance and operational capabilities of the Mars multi-rotor aircraft have been partially considered, mechatronic system design and autonomous flight control have not been fully addressed. Harbin Institute of Technology and China Academy of Space Technology jointly proposed a deployable Mars quadcopter for air patrol and sampling with a sample mass of 100 g. This paper presents a concept for a Mars quadcopter and its mission operations, including operational procedures and flight modes, to provide a framework for future Mars flight sampling missions. We describe the structure and avionics architecture of the Mars quadcopter. Then, we present the hardware and software design of the guidance, navigation, and control (GNC) system to illustrate the autonomous flight control method. Finally, we introduce the deployment mechanism of the Mars quadcopter. • A foldable Mars quadcopter improves the efficiency and flexibility of Mars sample return tasks. • Five-module avionics system augments the Mars quadcopter for survival and operation. • A navigation method combining inertial and binocular vision enables autonomous flight on Mars. • The guidance system based on mode commands can independently plan exploration operations. [ABSTRACT FROM AUTHOR]

The present study initially evaluates the feasibility of deep learning models to predict the flow and thermal fields of a wing with a symmetric wavy disturbance as the passive flow control. The present study developed the encoder–decoder (ED) and convolutional neural network (CNN) models to predict the characteristics of flow and heat transfer on the surface of three-dimensional wavy wings in a wide range of parameters, such as the aspect ratio, wave amplitude, wave number, and the angle of attack. Computational fluid dynamics (CFD) is used to generate the dataset of the deep learning models. Various tests are carried out to examine the predictive performance of the architectures for two deep learning models. The CNN and ED models demonstrated a quantitatively predictive performance for aerodynamic coefficients and Nusselt numbers, as well as a qualitative prediction for pressure contours, limiting streamlines, and Nusselt contours. The predicted results well reconstructed the spiral vortical formation and the separation delay by the limiting streamlines. It is expected that the present established deep learning methods are useful to perform the parametric study to find the conditions to provide efficient aerodynamic and thermal performances. [ABSTRACT FROM AUTHOR]

Accurate estimation of reference evapotranspiration (ETr) is important for irrigation planning, water resource management, and preserving agricultural and forest habitats. The widely used Penman–Monteith equation (ASCE-PM) estimates ETr across various timescales using ground weather station data. However, discrepancies persist between estimated ETr and measured ETr obtained from weighing lysimeters (ETr-lys), particularly in advective environments. This study assessed different machine learning (ML) models in comparison to ASCE-PM for ETr estimation in highly advective conditions. Various variable combinations, representing both radiation and aerodynamic components, were organized for evaluation. Eleven datasets (DT) were created for the daily timescale, while seven were established for hourly and quarter-hourly timescales. ML models were optimized by a genetic algorithm (GA) and included support vector regression (GA-SVR), random forest (GA-RF), artificial neural networks (GA-ANN), and extreme learning machines (GA-ELM). Meteorological data and direct measurements of well-watered alfalfa grown under reference ET conditions obtained from weighing lysimeters and a nearby weather station in Bushland, Texas (1996–1998), were used for training and testing. Model performance was assessed using metrics such as root mean square error (RMSE), mean absolute error (MAE), mean bias error (MBE), and coefficient of determination (R2). ASCE-PM consistently underestimated alfalfa ET across all timescales (above 7.5 mm/day, 0.6 mm/h, and 0.2 mm/h daily, hourly, and quarter-hourly, respectively). On hourly and quarter-hourly timescales, datasets predominantly composed of radiation components or a blend of radiation and aerodynamic components demonstrated superior performance. Conversely, datasets primarily composed of aerodynamic components exhibited enhanced performance on a daily timescale. Overall, GA-ELM outperformed the other models and was thus recommended for ETr estimation at all timescales. The findings emphasize the significance of ML models in accurately estimating ETr across varying temporal resolutions, crucial for effective water management, water resources, and agricultural planning. [ABSTRACT FROM AUTHOR]

Aiming at the overall design parameters and mission profile requirements of commuter aircrafts, according to the hydrogen-lithium propulsion system architecture scheme, the propulsion system parameter matching method and energy dynamic balance management strategy were proposed. A 1 9-seat commuter aircraft was used to select and manage the power plant and reserve energy. According to the selected distributed aerodynamic layout scheme, then the effects of propeller rotation directions on aircraft aerodynamic characteristics were analyzed with full factorial design of experiments, and the optimum propeller rotation direction configuration for aircraft cruise states was obtained. [ABSTRACT FROM AUTHOR]