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This research focuses on addressing a significant concern in the aviation industry, which is drag. The primary objective of this project is to achieve drag reduction through the implementation of riblets on a wing featuring the NACA 2412 aerofoil, operating at subsonic speeds. Riblets, with the flow direction on wing surfaces, have demonstrated the potential to effectively decrease drag in diverse applications. This investigation includes computational analysis within the ANSYS Workbench framework, employing a polyhedral mesh model. The scope of this research encompasses the analysis of both a conventional wing and a modified wing with riblets. A comparative analysis is conducted to assess variations in drag values between the two configurations. Parameters, including geometry, dimensions, and riblet placement at varying angles of attack, are explored to comprehend their impact on drag reduction. Notably, 15.6% and 23% reductions in drag were identified at a 16-degree angle of attack with midspan and three-riblet models, separately. The computational mesh and method were validated using appropriate techniques.

An UAV (Unmanned Aerial Vehicle) is an aircraft without an onboard pilot that has several functions. Mohinder is one of the fixed-wing UAVs used for mapping and monitoring areas. Currently, the Mohinder UNNES is adopted from other UAVs by reduced-scale X-UAV Talon. There are differences between dimensions and cruising speed among Mohinder and X-UAV Talon (Mohinder adaptation). The purpose of this study is to select the suitable Mohinder’s airfoil using XFLR 5 simulation using multi-criteria decision particularly the AHP (Analytical Hierarchy Process). AHP can break down the choosing into a hierarchy, compare each factor's importance, and use math to figure out the best choice based on the preferences. The selection criteria are Max Camber, Thickness α stall, Max L/Dmax, CLmax, and CL0, so then the basic airfoil shapes are AH 79-100 B, S1223 RTL, FX 63-120, dan EPPLER 395. Mohinder airfoil will be selected based on aerodynamic performance at Reynold number 200.000. The simulation results showed the AH 79-100 B airfoil has higher L/Dmax and Cl at angle of attack (AOT) -10° to 20° compared to airfoil MH-32 (Mohinder current airfoil)

The Mars surface is rugged and its environment is complex, the Mars UAVs provide a new idea for Mars exploration due to its high mobility and flexibility, and is an important paradigm for future deep space exploration.The differences between Mars and some relevant surface environmental parameters on Earth are compared, the main uses and difficulties that Mars UAVs need to be overcome are analyzed, and the importance of Mars UAV experimental platform is clarified. The technical features, functional advantages and disadvantages of the Mars UAV experimental platform developed by domestic and foreign research institutions are introduced in detail, and the need for the experimental platform to have a simulated Mars environment and measure relevant parameters is summarized. On this basis, the idea of building a Mars UAV experiment platform is proposed, the overall design ideas and thoughts are given, and the prospect of the application of the Mars aerodynamics experimental platform is made.

Accurate predictions of aerodynamic performance and near wake expansion around Horizontal Axis Wind Turbine (HAWT) rotors is pivotal for studying wind turbine wake interactions and optimizing wind farm layouts. This study introduces a novel engineering model centered on stall delay correction to enhance the precision of the Actuator Disk Method (ADM) predictions in both aerodynamic performance and near wake expansion around HAWT rotors. The model is developed based on a comprehensive study of the 3D lift coefficient evolution over the rotor blade, incorporating a shift parameter that considers both stall angle detection and radial decrement. The proposed approach demonstrates remarkable agreements, showcasing discrepancies as low as 7% for both loads and axial wake predictions. These quantifiable results underscore the effectiveness of the model in capturing intricate aerodynamic phenomena. Looking forward, the success of this approach opens avenues for broader applications, guiding future research in wind energy towards improved simulation accuracy and optimized wind farm designs.

Purpose: Leading a 4-km team pursuit (TP) requires high-intensity efforts above critical power (CP) that deplete riders' finite work capacity (W′), whereas riders following in the aerodynamic draft may experience some recovery due to reduced power demands. This study aimed to determine how rider ability and CP and W′ measures impact TP performance and the extent to which W′ can reconstitute during recovery positions in a TP race. Methods: Three TP teams, each consisting of 4 males, completed individual performance tests to determine their CP and W′. Teams were classified based on their performance level as international (INT), national (NAT), or regional (REG). Each team performed a TP on an indoor velodrome (INT: 3:49.9; NAT: 3:56.7; and REG: 4:05.4; min:s). Ergometer-based TP simulations with an open-ended interval to exhaustion were performed to measure individual ability to reconstitute W′ at 25 to 100 W below CP. Results: The INT team possessed higher CP (407 [4] W) than both NAT (381 [13] W) and REG (376 [15] W) (P <.05), whereas W′ was similar between teams (INT: 27.2 [2.8] kJ; NAT: 29.3 [2.4] kJ; and REG: 28.8 [1.6] kJ; P >.05). The INT team expended 104% (5%) of their initial W′ during the TP and possessed faster rates of recovery than NAT and REG at 25 and 50 W below CP (P <.05). Conclusions: The CP and rate of W′ reconstitution have a greater impact on TP performance than W′ magnitude and can differentiate TP performance level. [ABSTRACT FROM AUTHOR]

Vertical-axis wind turbines (VAWT) with Darrieus and Savonius rotors were studied based on the developed specialized package of computational aerodynamics. The flow structure around the Savonius and Darrieus rotors was numerically reconstructed, considering the mutual influence. From this reconstruction, the main stages of the vortex structure formation during the flow of the turbulent wind around the rotors were identified. Qualitative and quantitative assessments of the influence of the Savonius rotor on the total aerodynamic and energy characteristics of a VAWT were carried out. It is shown that the main contribution to the torque of the VAWT is due to the Darrieus rotor, mainly in the windward section of the trajectory. The Savonius rotor accounts for only a few percent of the total torque produced by the installation. The interaction of the Darrieus rotor blades with macrovortices from the Savonius rotor in the leeward part of the trajectory leads to a sharp drop in the torque coefficient. In the absence of a Savonius rotor, the vortices separated from supported tower are much smaller both in size and intensity. Therefore, their interaction with the blades of the Darrieus rotor does not lead to a significant change in the aerodynamic characteristics. A power characteristics comparison of two VAWTs showed that the torque coefficient is higher for wind turbines with only single Darrieus rotor. The developed approaches and techniques make it possible to reproduce real aerodynamic processes of flow most reliably around bodies of arbitrary shape and calculate their aerodynamic characteristics.

ABSTRACTTip loss correction is necessary for all aerodynamic computations based on the blade-element momentum theory (BEMT) that plays an essential role in wind turbine design. Glauert tip-loss correction, which is most widely used, assumes the rotor is lightly loaded and thus lose some accuracy for modern wind turbines that are highly loaded. In the present work, a new g-function involving the rotor’s thrust-coefficient is introduced, which connects the tip loss correction with the rotor’s load condition and reduces the error of the tip loss correction. Computational tests are performed on two rotors that are distinct in size and tip shape. The new g-function results in good consistency between the computed forces and the reference data, exhibiting excellent role in improving the accuracy of the BEMT computations. In general, the new g-function combines good effectiveness and applicability, and thus has great potential for engineering applications.

[This corrects the article DOI: 10.3389/frobt.2022.1033715.].

AbstractThe dynamic response of concrete structures reinforced with nanocomposites to supersonic airflow represents a critical aspect in aerospace and defense applications, necessitating accurate predictive models for enhanced structural integrity and performance. In this study, we introduce innovative deep neural networks (DNNs) as a novel approach to predict the dynamic behavior of such structures under supersonic airflow conditions. Traditional modeling techniques often face challenges in capturing the intricate interactions between material properties, structural geometry, and airflow dynamics, particularly in the presence of nanocomposite reinforcements. DNNs offer a promising solution by leveraging their ability to learn complex patterns and nonlinear relationships from extensive datasets. This paper presents a comprehensive framework for developing and deploying DNN-based models for dynamic prediction, encompassing network architecture design, training strategies, and data preprocessing techniques tailored to the unique characteristics of nanocomposite-reinforced concrete structures. Through a series of case studies and comparative analyses, we demonstrate the effectiveness and accuracy of DNNs in capturing the dynamic response of such structures to supersonic airflow, including phenomena such as vibration, flutter, and aerodynamic instability. Furthermore, we discuss the potential advantages and challenges associated with the adoption of DNNs in aerospace and defense applications, including model interpretability, computational efficiency, and data requirements. Finally, we outline future research directions and opportunities for further advancing the application of DNNs in addressing dynamic challenges in aerospace engineering and beyond. [ABSTRACT FROM AUTHOR]

For the problem of ventral support interference in a transonic-speed wind tunnel with the blended-wing-body aircraft NPU-BWB-300 installed, the numerical simulation method based on Reynolds-averaged Navier–Stokes (RANS) equations is used to study the influence law of aerodynamic characteristic interference with the variation of Mach numbers and angles of attack. Moreover, the characteristics of ventral support interference for blended-wing-body aircraft and conventional aircraft are compared. The relevant mechanism of the generation and change of ventral support interference is revealed by employing analysis of the body surface pressure, the shock wave of the strut, and the separation area between the strut and the aircraft. The aerodynamic characteristic interference obtained from the numerical simulation is linearized based on the principle of the least square method. Afterward, a numerical simulation correction method of ventral support interference in the transonic-speed wind tunnel for the blended-wing-body aircraft is developed. Finally, the test results after the corrections of ventral support interferences in the transonic-speed wind tunnel for NPU-BWB-300 are obtained, which is significant for the evaluation of current aerodynamic performances and subsequent optimization designs. [ABSTRACT FROM AUTHOR]

In the design of flapping-wing micro-size air vehicles capable of hovering, wings serve as the primary source of hovering power, making the analysis of aerodynamics and aerodynamic efficiency crucial. Traditional quasi-steady models treat the wings as single rigid plane, neglecting the deformable characteristics of flexible wings. This paper proposes a multi-plane method that, in conjunction with various design parameters of flexible wings in a two-dimensional plane, analyzes their deformation characteristics under the assumption of multiple planes in three-dimensional space, and describes the deformation of wings during flapping. By combining the quasi-steady aerodynamic model, aerodynamic analysis of the deformed wings can be conducted. The relationship between the slack angle, wing flapping position, and wing deformation are analyzed, along with their effects on aerodynamics and aerodynamic efficiency. Experiments validate the deformation patterns of wings during flapping and compare the simulated aerodynamic forces with measured ones. The results indicate that wing deformation can be accurately described by adjusting the parameters in the multi-plane method and that the aerodynamic analysis using this method closely approximates the average lift results. Additionally, the multi-plane method establishes a connection between wing morphology and aerodynamic forces and efficiency, providing valuable insights for aerodynamic analysis. [ABSTRACT FROM AUTHOR]

AbstractFlow-induced vibration is known as a prevalent phenomenon in various industries. As a result of the flow, dynamic fluid forces are generated, which lead to the excitation of the system. Multiphase flow, found commonly in both natural and industrial settings, including industrial plants, is a significant source of noise and vibration. In the two-phase flow, as a particular case of multiphase flow, flow configuration plays a major role in the system’s traits. Despite recent advancements in flow-induced vibration, it is still considered an unresolved topic. This research develops a new multi-physics simulation for the stability study of a two-directional functionally graded tilted curved cylindrical nanopipe conveying a liquid-gas two-phase flow. Nonlocal stress–strain gradient theory (NSGT) with two size-dependent parameters (nonlocal and length scale) is presented to simulate the current nanostructure. Newton’s second law has been employed to govern the resultant forces that act on a control volume at a differential fluid element of fluid. Hiring the finite element (FE) approach alongside the generalized differential quadrature role (GDQR), both the eigenvector and eigenvalue problems are presented for analyzing the characteristics of the nanosystem under various situations. An exhaustive parametric analysis is also provided to make clear the role of varied parameters such as velocity of fluid flow, aerodynamic pressure, air yaw angle, and gas volume fraction coefficient on the system’s fundamental frequency. [ABSTRACT FROM AUTHOR]

The response of airfoils to unsteady disturbances is a classic problem in the aerodynamics field. Many theoretical models have been proposed in the past to predict the unsteady aerodynamic forces of airfoils. However, these theories focused on individual airfoil motions or incoming flow disturbances, while the theoretical models for multiple disturbances still need to be developed. In this study, a theoretical model to predict the aerodynamic force of an oscillating airfoil encountering vertical gust is derived from a linear combination of Theodorsen's and Sears' theories. Experimental investigations involving a two-dimensional pitching airfoil encountering a sinusoidal vertical gust are carried out to examine the proposed theory. It is found that the theory effectively captures the trends in the unsteady lift of airfoils subjected to dual disturbances. However, it tends to overestimate the lift amplitude. Notably, when a quasi-steady correction is applied to the theory, the prediction accuracy is greatly improved. The theory correction agrees well with experiment at small pitching frequencies, while deviations exist at higher pitching frequencies. The temporal evolution of the flow velocity reveals that the velocity disturbance induced by the coupled disturbance around the airfoil conforms to the linear superposition of the velocities induced by each individual disturbance, consistent with the prediction of the vortex sheet model. As the pitching frequency increases, significant nonlinear effects appear near the trailing edge of the airfoil, which may be one key factor for the disparities between the theoretical predictions and the experimental lift at higher pitching frequencies. [ABSTRACT FROM AUTHOR]

Aeroelastic flutter is a dynamically complex phenomenon that has adverse and unstable effects on elastic structures. It is crucial to better predict the phenomenon of flutter within the scope of aircraft structures to improve the design of their wings. This review aims to establish fundamental guidelines for flutter analysis across subsonic, transonic, supersonic, and hypersonic flow regimes, providing a thorough overview of established analytical, numerical, and reduced-order models as applicable to each flow regime. The review will shed light on the limitations and missing components within the previous literature on these flow regimes by highlighting the challenges involved in simulating flutter. In addition, popular methods that employ the aforementioned analyses for optimizing wing structures under the effects of flutter--a subject currently garnering significant research attention--are also discussed. Our discussion offers new perspectives that encourage collaborative effort in the area of computational methods for flutter prediction and optimization. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effects of thrower-discus system rotation on performance in discus throwing. The resultant angular momentum of the thrower-discus system and direction cosines of the angular momentum vector were calculated from kinematic data at five critical instants of discus throwing for 28 female and 15 male elite discus throwers, and compared between their long and short trials in actual competition. Compared to short trials, elite female throwers' long trials had significantly less angular momentum at right foot takeoff and left foot takeoff (P ≤ 0.023), and significantly less top-to-left rotation at right foot takeoff, left foot takeoff, left foot touchdown, and release (P ≤ 0.007), and significantly greater right-to-left rotation at left foot touchdown and release (P ≤ 0.009) in long trials. Compared to their short trials, elite male throwers had significantly less top-to-left and top-to-front rotations at left foot touchdown (P ≤ 0.042), and significantly less total angular momentum at release (P = 0.043) in long trials. Elite discus throwers should control the amount of rotations of the thrower-discus system to reduce the top-to-left roll of the discus during the flight to extend the aerodynamic distance. [ABSTRACT FROM AUTHOR]

A computational model is developed to obtain a helicopter rotor blade's vibration characteristics and aerodynamic behavior. A mathematical model of the wake is also developed, consisting of fundamental wake geometry. A Bo 105 helicopter rotor blade is considered for computational aerodynamic analysis. A fluid–structure interaction model of the rotor blade with surrounding air is developed, where the finite element model of the blade is coupled with the computational fluid dynamics model of the surrounding air. The fluid–structure interaction model analyzes aerodynamic coefficients, velocity profiles, and pressure profiles. The resonance frequencies and mode shapes are also obtained by the computational method. A small-scale model of the rotor blade is manufactured, and experimental analysis of similar contemplation is conducted to validate the numerical results. Wind tunnel and vibration testing arrangements are used for the experimental validation of the aerodynamic and vibration characteristics, respectively. The wake and vortex analysis showed that the swirl velocity is minimum, and the axial velocity is maximum at the vortex center. The axial velocity decreases, and swirl velocity increases with increasing the distance from the vortex center to the core radius. Finally, an application of experimentally validated computational methodology for helicopter rotor blade to evaluate aerodynamic characteristics in a fluid–structure interaction environment along with the characterization of resonance properties is outlined where the results follow an expected pattern. [ABSTRACT FROM AUTHOR]

This study presents a design optimization of a circumferential feedback channel on the shroud casing between rotor trailing and leading edges to maximize the aerodynamic performance of a single-stage transonic axial compressor, NASA Stage 37, using three-dimensional Reynolds-averaged Navier–Stokes analysis (RANS) with the k-ε turbulence model. The location of the injection and bleeding ports, angles of injection, and bleeding were the most influential factors on the aerodynamic performance and were selected as the design variables. A hybrid genetic algorithm and particle swarm optimization algorithm coupled with three different surrogate models were utilized to maximize the peak adiabatic efficiency and stall margin of the transonic axial compressor. The optimization results for the circumferential feedback channel indicated that an increase in stall margin was achievable with a slightly reduced peak efficiency in comparison with that of the smooth casing. [ABSTRACT FROM AUTHOR]

The wheels of a passenger vehicle contribute to a significant part of the vehicle's aerodynamic drag. The previous research has shown that the flow is sensitive to small geometrical variations of the tyre, such as its shoulder profile and tread pattern. This work investigates the effect of altering the tyre profile in the transition region between the tyre and the rim by adding a so-called rim protector. Full-scale wind tunnel tests capturing forces, flow fields and surface pressures were conducted for three tyre variants in combination with two rim configurations on a crossover SUV. With a low rim protector, the forces and flow fields were similar to the reference tyre without a rim protector for both rims. With a wide, protruding, rim protector on the open rim, a larger and more outwashed front wheel wake was obtained with differences in the vortex structures, resulting in a drag penalty of 0.017 C D . The altered front wheel wake reduced the shielding of the rear wheel, resulting in differences in the rear wheel wake and base pressure. With a closed rim, the differences with the wide rim protector were much smaller with only a slight drag increase compared to the reference, demonstrating that there can be a strong interaction between the tyre and rim design. [ABSTRACT FROM AUTHOR]

Introduction: Diabetes mellitus type 2 is a growing health concern that affects several systems in the body, among which is the phonatory apparatus. Voice may be affected in view of the high prevalence of myopathy and neuropathy in diseased subjects. The authors aimed to answer the following question: does type 2 diabetes have an effect on voice? Methods: The systematic review included search terms such as "speech, voice, larynx, glucose, diabetes, and hyperglycemia." The search strategy yielded 221 articles, only five of which satisfied the inclusion criteria. Articles were considered for inclusion using the PRISMA method. Analysis included 321 patients with type 2 diabetes mellitus and 171 controls. All studies included were case-control studies except for one study which was an observational cohort. Six parameters were chosen as endpoints for the systematic review and meta-analysis: the presence/absence of voice complaints, fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, and maximum phonation time. Results: There was no significant difference in the prevalence of voice complaints (i.e., hoarseness) between diabetic patients and control groups. There was also no significant difference in any of the acoustic and aerodynamic measures between patients with type 2 diabetes and controls. These findings can be ascribed to the high resilience of the laryngeal muscles to the adverse effect of systemic diseases. Conclusion: There is no consensus in the literature that the prevalence of voice symptoms in diabetic patients is significantly higher than that reported in healthy subjects. [ABSTRACT FROM AUTHOR]

We study the steady aerodynamic field and loadings about a thin flat plate placed in a wind tunnel under non-continuum conditions. Considering a two-dimensional straight tunnel configuration, the flow is driven by either density or temperature differences between the inlet and outlet tunnel reservoirs, producing a pressure gradient across the channel. Focusing on highly rarefied conditions, we derive a semi-analytic description for the gas flow field in the free-molecular limit for diffuse- and specular-wall configurations. The solution is valid at arbitrary differences between the inlet and outlet reservoirs as well as plate angles of attack α. The results are compared with direct simulation Monte Carlo calculations, indicating that the free-molecular description is valid through O(1) plate-size-based Knudsen numbers. The aerodynamic lift and drag forces are evaluated and their variations with α, reservoir conditions, and tunnel size are analyzed. At a fixed pressure ratio between the outlet and inlet reservoirs, the density-driven flow generates higher aerodynamic loads compared with its counterpart temperature-driven configuration, in line with the associated larger mass flow rate in the former. The results are discussed in light of the existing rarefied-gas description of the free-stream (non-confined) problem. [ABSTRACT FROM AUTHOR]

Quick and high-fidelity updates about aerodynamic loads of large-scale structures, from trains, planes, and automobiles to many civil infrastructures, serving under the influence of a broad range of crosswinds are of practical significance for their design and in-use safety assessment. Herein, we demonstrate that data-driven machine learning (ML) modeling, in combination with conventional computational methods, can fulfill the goal of fast yet faithful aerodynamic prediction for moving objects subject to crosswinds. Taking a full-scale high-speed train, we illustrate that our data-driven model, trained with a small amount of data from simulations, can readily predict with high fidelity pressure and viscous stress distributions on the train surface in a wide span of operating speed and crosswind velocity. By exploring the dependence of aerodynamic coefficients on yaw angles from ML-based predictions, a rapid update of aerodynamic forces is realized, which can be effectively generalized to trains operating at higher speed levels and subject to harsher crosswinds. The method introduced here paves the way for high-fidelity yet efficient predictions to capture the aerodynamics of engineering structures and facilitates their safety assessment with enormous economic and social significance. [ABSTRACT FROM AUTHOR]

In this paper, we numerically studied the effect of stroke deviation on the aerodynamic performance of the three-dimensional flapping wing in forward flight at a low Reynolds number. Six deviation motion patterns with different stroke deviation amplitudes were investigated. The results show that the distinct patterns exert a substantial influence on the aerodynamic forces of the flapping wing, with a more pronounced effect at higher values of deviation amplitude. For most patterns, stroke deviation enhances either lift or thrust performance unilaterally. The maximum lift and thrust of the wing with deviation motion can be 37% and 35% larger than that of the wing without deviation motion. A detailed analysis of typical flow characteristics underscores the pivotal role of deviation motion in aerodynamic force generation. Finally, two artificially created innovative deviation motion patterns are proposed, which exhibit an exceptional capacity to augment thrust by up to 123% or enhance comprehensive aerodynamic performance significantly. These findings establish a theoretical foundation for designing high-performance flapping-wing micro-air vehicles. [ABSTRACT FROM AUTHOR]

In the present study, the evolutionary multi-objective optimization is employed to design the optimum amplitude and wavelength of sinusoidal leading-edge tubercles for the NACA0012 (National Advisory Committee for Aeronautics) airfoil to improve its aerodynamic performance at Reynolds number of 5.0 × 104 than that of the NACA0012 smooth leading-edge or baseline airfoil. Here, the optimum tubercle is found to have an amplitude of 11.71% and a wavelength of 25% of the baseline airfoil chord, respectively. Through a combination of in-house water tunnel experiments and numerical simulations, it is additionally established that the optimized tubercle airfoil exhibits superior lift and reduced drag characteristics compared to the baseline airfoil, particularly in the post-stall high angle of attack regime. Furthermore, it is noticed that the optimized tubercle design enhances the gap between large separation regions or stall cells along the tubercle airfoil span during the post-stall regime. Consequently, a more pronounced attached flow regime is developed between the consecutive stall cells, contributing to the tubercle airfoil's improved aerodynamic characteristics compared to the baseline airfoil. Our investigations also revealed that the formation and arrangement of the stall cells on the tubercle airfoil span are associated with a biased wake mechanism similar to the one observed in the wake of side-by-side arranged circular cylinders. [ABSTRACT FROM AUTHOR]

Ducted rotor-only low-pressure axial fans play an integral role in automotive thermal management. The tightly packed under-hood region and down-stream heat-exchanger shape limit the fan diameter. In order to circumvent this limitation, multiple cooling fans of small diameters are tightly packaged and placed in parallel. Currently, there is limited scientific work, that study the aerodynamics of low-pressure axial fans when installed in parallel. This work aims to quantify the aerodynamic performance and the flow-field as a result of installing low-pressure axial fans in parallel through computational fluid dynamics (CFD). Publicly available experimental data from Friedrich-Alexander University is used for the validation of the numerical setup. Three-dimensional, full-annulus, unsteady Reynolds-averaged Navier-Stokes (URANS) analysis has been performed for both a single-fan and two-fans installed in parallel and their respective aerodynamic performance has been compared for the operation condition identified as the best efficiency point in experiments. Only small differences are observed in the overall aerodynamic performance of the two-fans in parallel compared to a single-fan. A circumferential nonuniformity in the form of a local high-pressure zone at the inlet of the fan is observed when the two-fans are placed in parallel. The resulting circumferential nonuniformity is quantified, both in space and time. A strong correlation is found between the pressure fields of the two-fans installed in parallel. [ABSTRACT FROM AUTHOR]

The aerodynamics and flowfield of a rectangular semiwing equipped with four four-bladed propellers and a 40%-chord full-span plain trailing-edge flap were investigated by using force balance and particle image velocimetry (PIV). The distributed electric propulsion (DEP) wing was tilted from zero to 90-deg angle of attack. The maximum lift coefficient, lift-curve slope, and stall angle of the DEP wing were found to increase significantly with increasing propeller rotation. The DEP wing also exhibited a gradual stall in contrast to the sudden stall of the baseline wing. The lift coefficient of the DEP wing positioned vertically at 90 deg was also found to be greatly increased with increasing propeller rotation. Regardless of the magnitude of propeller rotation, the general pattern and behavior of the lift curve were consistent. The deployment of the flap led to a further increase in the maximum lift coefficient and lift-curve slope but an earlier stall and an increased drag of the DEP wing as compared to the unflapped wing. The flap deflection also led to a lowered lift coefficient in the poststall angle-of-attack regime as compared to the unflapped DEP wing. Gurney flap was also employed to further increase the lift generation of the DEP wing. The lift augmentation produced by the propeller slipstream was supplemented by the PIV flowfield measurements. [ABSTRACT FROM AUTHOR]

This study presents an aerodynamic analysis of the 30P30N high-lift three-element wing under varying the angle of attack (α = 5°, 9°, and 23°) at a constant Reynolds number (Rec = 750, 000) by means of large eddy simulations (LES). Baseline results were validated against existing literature, demonstrating good agreement. The increase of the angle of attack entails higher values of lift but also, increased values of drag. At α = 23°, a recirculation area appears above the flap, this being the signature of the stall conditions. This is related to the adverse pressure gradient that develops along the main suction side and the separation of the streamlines in its wake. Actuation strategies using synthetic jets were explored to mitigate this flow separation at this angle of attack, and thus, enhance the efficiency of the wing. Three actuation cases with the jets located on the main wing, on the flap, and on both elements at the same time were investigated. While some improvements are observed with the actuation, particularly in the combined actuation case, the overall wing efficiency was only marginally enhanced. Challenges in achieving significant improvements were attributed to complex flow interactions and the dominance of pressure forces, which affect both the lift and the drag coefficients at the same time. [ABSTRACT FROM AUTHOR]

The divergence of a thin elastic plate reinforced by stiff ribs (stringers) with cyclic symmetry is considered, with some approximations. The incoming air flow is assumed to be supersonic, and so the aerodynamic load is described by means of approximate piston theory, for a steady temperature field. In taking account of the composite structure, attention is paid to the configuration of the stiffening ribs; a contact formulation is adopted. The lower critical velocity of the incoming air flow is determined by the first approximation, and its dependence on the number of stiffening ribs is investigated. It is shown numerically that, with increase in the distance between the ribs, the critical rate of divergence approaches its value for a smooth plate. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Transactions B: Applications is the property of International Journal of Engineering (IJE) 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 Polytechnic is the property of Journal of Polytechnic 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 Polytechnic is the property of Journal of Polytechnic 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.)

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]

Summary: This work presents details and assesses implicit and adaptive mesh‐free CFD modelling approaches, to alleviate laborious mesh generation in modern CFD processes. A weighted‐least‐squares‐based, mesh‐free, discretisation scheme was first derived for the compressible RANS equations, and the implicit dual‐time stepping was adopted for improved stability and convergence. A novel weight balancing concept was introduced to improve the mesh‐free modelling on highly irregular point clouds. Automatic point cloud generations based on strand and level‐set points were also discussed. A novel, polar selection approach, was also introduced to establish high‐quality point collocations. The spatial accuracy and convergence properties were validated using 2D and 3D benchmark cases. The impact of irregular point clouds and various point collocation search methods were evaluated in detail. The proposed weight balancing and the polar selection approaches were found capable of improving the mesh‐free modelling on highly irregular point clouds. The mesh‐free flexibility was then exploited for adaptive modelling. Various adaptation strategies were assessed using simulations of an isentropic vortex, combining different point refinement mechanisms and collocation search methods. The mesh‐free modelling was then successfully applied to transonic aerofoil simulations with automated point generation. A weighted pressure gradient metric prioritising high gradient regions with large point sizes was introduced to drive the adaptation. The mesh‐free adaptation was found to effectively improve the shock resolution. The results highlight the potential of mesh‐free methods in alleviating the meshing bottleneck in modern CFD. [ABSTRACT FROM AUTHOR]