Straight Wing Research Articles

Determination of the critical velocity of a straight wing with a high aspect ratio

An aerodynamic problem on an air flow around a large aspect ratio rectangular wing is investigated in this study. According to the theory of Vlasov, the wing is considered to be a thin rod. External loads are assumed to be proportional to the airfoil angle of attack related to the dimensionless coefficient of the lift and the pitching moment coefficient. These coefficients depend on the airfoil parameters and the Mach number M and are determined by experimental measurements for subsonic and supersonic velocities. In this case, to define the unstable cases of the wing, one bases on the Lyapunov stability theory. Equations of bending and torsional free vibrations have resulted. Based on the analysis of natural frequencies (eigenfrequencies), it is possible to determine the changing positions of the real part and the imaginary part of the characteristic equation solution. These positions can cause instabilities for the wing such as torsional divergence and flutter.

Effect of vortex generator spanwise height distribution pattern on aerodynamic characteristics of a straight wing

Vortex generator (VG) is a passive flow control technology, which can effectively inhibit flow separation. Recently, significant research efforts have been devoted to the study on the application of VG in airfoil, wing/blade and aircraft flow separation inhibition. However, the research on the variable height distribution of VG along the wingspan still lacks. This study focuses on the experimental investigation of the influence of variable height distribution of ramp VG on aerodynamic characteristics. First, VG was designed, such that it was composed of two parts, one fixed region and one deformed region, which allowed for height modification. The height of VGs along the wingspan presented equal-height, triangular and trapezoidal distribution, forming a total of 15 VG layouts. Then, the connection mode of the model, the change of angle of attack and the collection and processing of aerodynamic data were introduced. Finally, a wind tunnel experiment was performed to investigate the influence of height distribution of VG on aerodynamic characteristics of wing. The experimental results show that: (1) the height distribution of the three types of VGs could inhibit the stall flow and improve the aerodynamic performance of the wing; (2) “Triangular translation 3” and “Trapezoidal translation 2” were the best layouts, both of which could increase the maximum lift coefficient, delay stall, and significantly increase the lift-to-drag ratio at high angle of attack; (3) the influence of VG height and position factors on wing stall characteristics was analyzed by using the rough set theory, and the key position information of VG arrangement was provided. This study indicates that the variable height distribution is obviously better than the equal height distribution, which can provide ideas and references for the active control of variable height distribution of VGs.

Unsteady Aerodynamic Design of a Flapping Wing Combined with a Bionic Wavy Leading Edge

Based on the bionic design of the humpback whale fin, a passive flow control method is proposed to obtain greater flapping lift by applying the wavy leading edge structure to the straight symmetrical flapping wing. The leading edge of the conventional flapping wing is replaced by the wavy shape represented by regular trigonometric function to form a special passive flow control configuration imitating the leading edge of the humpback whale fin. The dynamic aerodynamic performance and flow field characteristics of straight wing and wavy leading edge flapping wing with different parameters are compared and analyzed by CFD numerical simulation. The simulation results show that the wavy leading edge structure changes the flow field of the baseline flapping wing and reduces the pressure on the upper surface of the flapping wing during the process of downward flapping, thereby increasing the pressure difference between the upper and lower surfaces of the flapping wing and increasing the lift. The sensitivity analysis of the design parameters shows that in order to obtain the maximum lift coefficient while losing the least thrust, the smaller amplitude should be selected on the premise of selecting the smaller wavelength. Among the configurations of different design parameters calculated in this paper, the optimal wavy leading edge flapping wing configuration increases the time average lift coefficient by 32.86% and decreases the time average thrust coefficient by 14.28%. Compared with the straight wing, it has better low-speed flight and can withstand greater take-off weight.

Дослідження впливу параметрів глибокорозпушувача та комбінації робочих органів на ефективність обробітку ґрунту

The paper proves the expediency of deep subsurface tillage with combined chisel deep tillers and raises the question of the expediency of studying the influence of tillage unit parameters and a combination of operating parts on the efficiency of tillage. Existing research addresses the issues of soil monolith destruction, interaction of certain elements and operating parts with soil particles, construction of statistical models of the operation of certain elements of tillage units, search for rational forms of surfaces of operating parts and the ways to reduce overall traction resistance of different deep tillers, but the assessment of the quality of operation of such tillage units depending on their design, combination of operating parts and parameters has not been sufficiently studied. To study the parameters of a deep tiller, a prototype was made, which is actually a full-fledged tillage unit with three chisel tines with a straight riser, a chisel, a tooth and wings. The design of the experimental deep tiller is made in such a way that the position of the chisel tines on the unit frame can be changed on the brackets in a wide range, both between rows and in terms of the working width of the unit. In addition, the deep tiller can be operated with different variants of the toothed roller. After selecting the most significant factors and the interval of their values based on the methodology for planning a multivariate experiment, studies were conducted to obtain a statistical mathematical model and response surfaces for tillage efficiency. The obtained regression equation was tested for reproducibility and adequacy, and the graphical display of the research results allows obtaining the desired design parameters and operating modes of the tillage unit. Experimentally found areas of rational values at which the quality of soil pulverization is equal to 70...75%, which is achieved at the depth of loosening with chisel tines 32...42 cm, the distance between the chisel tines in one row 80... 100 cm, distance between rows of chisel tines 40...55 cm, tillage speed 8...9.5 km/h, depth of wings on the tine riser 24...27 cm and number of additional operating parts (toothed rollers) 2 pcs.

Hysteresis and Asymmetry of the Aerodynamic Characteristics of Aircraft Model with High Aspect Ratio Straight Wing under the Flow Separation

Hysteresis and Asymmetry of the Aerodynamic Characteristics of Aircraft Model with High Aspect Ratio Straight Wing under the Flow Separation

Modern Implementation and Evaluation of Lifting-Line Theory for Complex Geometries

A numerical lifting-line method (implemented in an open-source software package) is presented that can accurately estimate the aerodynamics of wings with arbitrary sweep, dihedral, and twist. Previous numerical lifting-line methods have suffered from grid convergence challenges and limitations in accurately modeling the effects of sweep, or have relied on empirical relations for swept-wing parameters and have been limited in their application to typical wing geometries. This work presents novel improvements in accuracy, flexibility, and speed for complex geometries over previous methods. In the current work, thin-airfoil theory is used to correct section lift coefficients for sweep, providing a more general closure to the lifting-line problem. A linearized solution is presented, which can be used as a rapid approximation for the full solution, or as an initial guess for the nonlinear system of equations to speed convergence. Sensitivities to model parameters are investigated, and appropriate recommendations for these parameters are given. Agreement with Prandtl’s classical lifting-line method is excellent in the case of straight wings. Comparison with experimental data shows that this method can reasonably predict lift, drag, and lift distribution for a range of wing configurations. The speed and accuracy of this method make it well-suited for preliminary design and optimization.

Study on flutter characteristics of NACA0012 flexible straight wing with high-aspect-ratio

采用三维雷诺平均N-S方程和S-A湍流模型求解展弦比为16的NACA0012弹性平直机翼的非定常气动力, 结合机翼动力学方程, 建立了机翼颤振时域分析方法。利用该方法对机翼的颤振特性、颤振过程中的变形和振动响应, 以及瞬时流场进行数值模拟和分析, 并研究材料刚度和密度对机翼颤振速度和频率的影响。结果表明, 由于展弦比较大, 且材质轻柔, 机翼会出现一定幅度的静弯曲变形。第二阶(垂向弯曲)和第三阶(扭转)振动模态的耦合作用是机翼发生颤振的原因, 且颤振频率介于这两阶模态固有频率之间。对比不同材料刚度和密度下机翼的颤振速度和频率, 发现材料刚度的增大会提高颤振速度和频率, 材料密度的增大会使颤振速度先降低然后趋于不变, 颤振频率一直降低。

Control of flow separation over a wing model with plasma synthetic jets

An array of 30 plasma synthetic jet actuators (PSJAs) is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model. The lift and drag of the wing model are measured by a force balance, and the velocity fields over the suction surface are captured by a particle imaging velocimetry system. Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases. The flow separation can be suppressed effectively by the PSJAs array. The best flow control effect is achieved at a dimensionless discharge frequency of F + = 1, with the peak lift coefficient increased by 10.5% and the stall angle postponed by 2°. To further optimize the power consumption of the PSJAs, the influence of the density of PSJAs on the flow control effect is investigated. A threshold of the density exits (with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research), below which the flow control effect starts to deteriorate remarkably. In addition, for comparison purposes, a dielectric barrier discharge (DBD) plasma actuator is installed at the same location of the PSJAs. At the same power consumption, 4.9% increase of the peak lift coefficient is achieved by DBD, while that achieved by PSJAs reaches 5.6%.

Pitch/Plunge Equivalence for Dynamic Stall of Unswept Finite Wings

Pitch/plunge equivalence for deep dynamic stall of a straight finite wing is considered by employing large-eddy simulations. The flowfields are computed with a well-established time-implicit high-fidelity large-eddy simulation approach. The wing has a moderate aspect ratio of and a NACA 0012 section incorporating a rounded tip. The flow parameters are a freestream Mach number of and chord Reynolds numbers of . Pure pitching and equivalent plunging maneuvers are considered with a reduced frequency of and minimum and maximum effective angles of attack of 4 and 22 deg, respectively. The pitch and plunge dynamic stall cases are compared in detail in terms of the unsteady three-dimensional flow structure, surface pressure, and loading. Differences in the lift and moment coefficient are shown to be correctable, employing a steady thin-airfoil theory for a cambered airfoil that accounts for the rotation-induced apparent camber present in the pitching case. This pitch/plunge equivalence is extendable to the dynamic stall of a swept wing, as demonstrated in another paper by the authors [“Pitch–Plunge Equivalence for Dynamic Stall of Swept Finite Wings,” AIAA Journal (submitted for publication)].

Pitch/Plunge Equivalence for Dynamic Stall of Swept Finite Wings

A high-fidelity numerical study is undertaken to expand the notion of pitch/plunge equivalence to finite, swept wings undergoing deep-dynamic stall and builds upon the analysis of straight wings in another paper by the authors [“Pitch/Plunge Equivalence for Dynamic Stall of Unswept Finite Wings,” AIAA Journal (submitted for publication)]. The wing has an aspect ratio of with a NACA 0012 section, a rounded tip, and a sweep angle of ; it operates at a Reynolds number of and a Mach number of . Equivalent pure-pitch and pure-plunge motions at two different reduced frequencies are considered to assess pitch-induced apparent camber on the wing and its effects on the three-dimensional flow structure, surface topology, and aerodynamic loading. Regardless of the motion type or rate, the wing undergoes dynamic tip stall that is initiated through the outboard separation of a dynamic stall vortex as it lifts off the surface and forms into an arch vortex before ejecting into the wake. The pitching cases exhibit an advanced development and evolution in time of these features that are observed as variable amplifications of the aerodynamic loading, which is due predominantly to an apparent camber effect. Corrections to the total and sectional lift and moment coefficients are explored by extending steady thin-airfoil theory to pitching swept wings. Remarkably, the corrected plunge-equivalent histories provide a full collapse of the force and moment responses between the pitching and plunging cases, despite the delayed behavior of the flow structure. This equivalence and the similar process of dynamic stall should facilitate the comparison of experiments and/or simulations employing different motion types, even for finite-aspect-ratio and swept wings.

Experimental and numerical analysis of humpback whale inspired tubercles on swept wings

PurposeWith aims to increase the aerodynamic efficiency of aerodynamic surfaces, study on flow control over these surfaces has gained importance. With the addition of flow control devices such as synthetic jets and vortex generators, the flow characteristics can be modified over the surface and, at the same time, enhance the performance of the body. One such flow control device is the tubercle. Inspired by the humpback whale’s flippers, these leading-edge serrations have improved the aerodynamic efficiency and the lift characteristics of airfoils and wings. This paper aims to discusses in detail the flow physics associated with tubercles and their effect on swept wings.Design/methodology/approachThis study involves a series of experimental and numerical analyses that have been performed on four different wing configurations, with four different sweep angles corresponding to 0°, 10°, 20° and 30° at a low Reynolds number corresponding to Rec=100,000.FindingsResults indicate that the effect of tubercles diminishes with an increase in wing sweep. A significant performance enhancement was observed in the stall and post-stall regions. The addition of tubercles led to a smooth post-stall lift characteristic compared to the sudden loss in the lift with regular wings. Among the four different wings under observation, it was found that tubercles were most effective on the 0° configuration (no sweep), showing a 10.8% increment in maximum lift and a 38.5% increase in the average lift generated in the post-stall region. Tubercles were least effective on 30° configuration. Furthermore, with an increase in wing sweep, co-rotating vortices were distinctly observed rather than counter-rotating vortices.Originality/valueWhile extensive numerical and experimental studies have been performed on straight wings with tubercles, studies on the tubercle effect on swept wings at low Reynolds number are minimal and mainly experimental in nature. This study uses numerical methods to explore the complex flow physics associated with tubercles and their implementation on swept wings. This study can be used as an introductory study to implement passive flow control devices in the low Reynolds number regime.

Flapping wing propulsion: Comparison between discrete vortex method and other models

Cetacean propulsion by a periodic flapping motion of their fluke is considered and studied on a benchmark flexible straight wing. The aim of the study was to validate low-order models for this configuration. First, the two-dimensional rigid case is investigated, comparing the aerodynamic performance of the airfoil periodic motion vs the reduced frequency, with published data and unsteady Reynolds-averaged numerical simulation results. It appears that viscous drag modeling must be added to the discrete vortex method, in order to obtain sensible thrust results, for Garrick frequencies below 2. All high- and low-order models agree at the remarkable Garrick frequency of 1.82, although the experiment shows a lower efficiency of about 25%. The positions of the shed vortices match comparing the unsteady Reynolds-averaged numerical simulation and the discrete vortex method. Then, the three-dimensional leading-edge-suction-parameter modulated discrete vortex method is extended, by means of a lifting line theory. A modification of the method is proposed in order to consider wing dihedral, resulting from the spanwise flexibility. The configuration considers a reduced frequency of 1.82. Three types of spanwise wing flexibility are examined. For the inflexible and flexible cases, a reasonable agreement is observed between the different methods for each coefficient. The intermediate flexible wing provides a better thrust coefficient, while excessive flexibility proves to be detrimental. Vorticity fields are compared with previously published data for the three wings. For the highly flexible wing and the right choice of deformation parameters, the discrete vortex method produces reliable results.

Six new species of Amblypsilopus Bigot (Diptera: Dolichopodidae: Sciapodinae) and a key to species of the Afrotropical mainland

Six new species of Amblypsilopus Bigot, 1888 from the Afrotropical region are described and illustrated: A. gabonensis sp. nov. from Gabon, A. martini sp. nov., A. mufindiensis sp. nov. and A. udzungwensis sp. nov. from Tanzania, A. milleri sp. nov. from South Africa, and A. spiniscapus sp. nov. from Ivory Coast. Amblypsilopus gabonensis sp. nov. and A. spiniscapus sp. nov. are remarkable in having a setose antennal scape. Amblypsilopus martini sp. nov. and A. mufindiensis sp. nov. are peculiar in bearing very long setae on the antennal pedicel, mesonotum and scutellum. Amblypsilopus milleri sp. nov. is considered a member of the South African A. fasciatus species group despite its unmodified wing venation. The new species differ also from other similar representatives of the genus in the morphology of the male cercus and the male secondary sexual characters on the legs. The male of A. bevisi (Curran, 1927) is described for the first time. The following species described from females are considered doubtful (nomina dubia): A. flavicollis (Becker, 1923), A. rectangularis (Parent, 1937), A. sudanensis (Parent, 1939) and A. tropicalis (Parent, 1933). Amblypsilopus subfascipennis (Curran, 1926) has a strongly sinuate wing vein dm-m and is transferred to Chrysosoma Guérin-Méneville, 1831 (comb. nov.). Chrysosoma ungulatum Parent, 1941 from Príncipe with an almost straight vein dm-m is transferred to Amblypsilopus (comb. nov.). Chrysosoma centrale Becker, 1923 from Tanzania also has a straight wing vein dm-m and modified fore tarsus, being very close in habitus to A. steelei Grichanov, 1996, and is also transferred to Amblypsilopus (comb. nov.). Chrysosoma asperum Parent, 1933 from South Africa has the same characters, is almost identical to South African A. bevisi and is also transferred here to Amblypsilopus (comb. nov.) and newly synonymized with A. bevisi (syn. nov.). Presently, 66 reliable species of Amblypsilopus are known from the Afrotropical region, including 37 from the Afrotropical mainland. A revised identification key to males of species of the Afrotropical mainland is provided. New records are given for some known species. The species diversity of the Afrotropical fauna and variability of morphological characters in the genus Amblypsilopus are briefly discussed.

Design of a Flap for Straight Wing of Unmanned Aerial Vehicle

In the paper hereby, design of a single stage Fowler flap is proposed. The flap is meant to increase lifting abilities of a straight wing at low speeds. It is applicable to small-sized remotely controlled unmanned aerial vehicles widely available to hobbyists. The design process included thorough analysis of flow around a wing foil in case of both retracted and deployed flap. To obtain aerodynamic coefficients values at different angles of attack and Reynolds numbers was a primary goal. In addition, a linkage mechanism was developed to make it possible for the flap to move along a complex path. Various plots and charts are depicted thereafter with sole purpose of providing better understanding of the idea.

Flow control by distributed suction behind three-dimensional roughness element on the straight wing model

The paper is devoted to the close investigation of the flow over perforated suction section in the presence of the three-dimensional roughness element. Measurements were conducted over the surface of the straight wing with and without suction. It was shown that distributed suction allows diminishing the intensity of longitudinal structure. Also the boundaries of the effective suction usage were found.

CFD Analysis of the Influence of the Front Wing Setup on a Time Attack Sports Car’s Aerodynamics

In time attack races, aerodynamics plays a vital role in achieving short track times. These races are characterized by frequent braking and acceleration supported by aerodynamic downforce. Usually, typical cars are modified for these races by amateurs. Adjusting the aerodynamic solutions to work with bodies developed for other flow conditions is difficult. This paper presents the results of a numerical analysis of the effects of installing a straight wing in front of or above the body on the modified vehicle system’s aerodynamic characteristics, particularly on the front wheels’ aerodynamic downforce values. The paper presents the methodology and results of calculations of the aerodynamic characteristics of a car with an additional wing placed in various positions in relation to the body. The numerical results are presented (Cd, Cl, Cm, Clf, Clr), as well as exemplary pressure distributions, pathlines, and visualizations of vortex structures. Strong interactions between the wing operation and body streamline structure are shown. An interesting and unexpected result of the analysis is that the possibility of obtaining aerodynamic downforce of the front wheels is identified, without an increase in aerodynamic drag, by means of a wing placed in a proper position in front of the body. A successful attempt to balance the additional downforce coming from the front wing on the front axle is made using a larger spoiler. However, for large angles of attack, periodically unsteady flow is captured with frequency oscillations of ca. 6–12 Hz at a car speed of 40 m/s, which may interfere with the sports car’s natural suspension frequency.

Triglobal infinite-wing shock-buffet study

This article uses triglobal stability analysis to address the question of shock-buffet unsteadiness, and associated modal dominance, on infinite wings at high Reynolds number, expanding upon recent biglobal work, aspiring to elucidate the flow phenomenon's origin and characteristics. Infinite wings are modelled by extruding an aerofoil to finite aspect ratios and imposing a periodic boundary condition without assumptions on spanwise homogeneity. Two distinct steady base flows, spanwise uniform and non-uniform, are analysed herein on straight and swept wings. Stability analysis of straight-wing uniform flow identifies both the oscillatory aerofoil mode, linked to the chordwise shock motion synchronised with a pulsation of its downstream shear layer, and several monotone (non-oscillatory), spatially periodic shock-distortion modes. Those monotone modes become outboard travelling on the swept wing with their respective frequencies and phase speeds correlated with the sweep angle. In the limiting case of very small wavenumbers approaching zero, the effect of sweep creates branches of outboard and inboard travelling modes. Overall, triglobal results for such quasi-three-dimensional base flows agree with previous biglobal studies. On the contrary, cellular patterns form in proper three-dimensional base flow on straight wings, and we present the first triglobal study of such an equilibrium solution to the governing equations. Spanwise-irregular modes are found to be sensitive to the chosen aspect ratio. Nonlinear time-marching simulations reveal the flow evolution and distinct events to confirm the insights gained through dominant modes from routine triglobal stability analysis.

Karakteristik Morfologi Serangga Yang Berpotensi Sebagai Hama Pada Perkebunan Kelapa (Cocos nucifera L.) di Desa Tirta Kencana Kecamatan Makarti Jaya Kabupaten Banyuasin

ABSTRACK The insect morphology research coconut ( Cocos nucifera L.) in Tirta Kencana village, Makarti Jaya district, Banyuasin regency was conducted in April-Mei 2021. The research objective was to determine the morphology of insect pest on coconut plants ( Cocos nucifera L.) in Tirta Kencana village. This study uses a purposive sampling method, that are three capture methods ( insecting net , fitfall trap , light trap ). The observation parameters include the type of head, mouth, antennae,wings and legs. The results of the study obtained 123 insects from 6 orders, 9 species. The insects that have potential as the pests consist of 2 orders and 5 species, there are Apogonia expeditionis , Orycthes rhinoceros , Oxya chirensis , Rhynchophorus ferrugineus and Valanga SP. Biting-chewing mouth type, 2 head types, namely Prognatus and Hypognatus, Lamellate and Filiform antenna types, Hard and Straight wing types, Cursorial and Saltatorial leg types. Keywords : Coconut Plants ( Cocos nucifera L.), Insect Pests, Morphological Characteristics.

Artificial Intelligence to Automatically Assess Scan Quality in Hip Ultrasound.

Since it is fast, inexpensive and increasingly portable, ultrasound can be used for early detection of Developmental Dysplasia of the Hip (DDH) in infants at point-of-care. However, accurate interpretation\is highly dependent on scan quality. Poor-quality images lead to misdiagnosis, but inexperienced users may not even recognize the deficiencies in the images. Currently, users assess scan quality subjectively, based on image landmarks which are prone to human errors. Instead, we propose using Artificial Intelligence (AI) to automatically assess scan quality. We trained separate Convolutional Neural Network (CNN) models to detect presence of each of four commonly used ultrasound landmarks in each hip image: straight horizontal iliac wing, labrum, os ischium and midportion of the femoral head. We used 100 3D ultrasound (3DUS) images for training and validated the technique on a set of 107 3DUS images also scored for landmarks by three non-expert readers and one expert radiologist. We got AI ≥ 85% accuracy for all four landmarks (ilium = 0.89, labrum = 0.94, os ischium = 0.85, femoral head = 0.98) as a binary classifier between adequate and inadequate scan quality. Our technique also showed excellent agreement with manual assessment in terms of Intraclass Correlation Coefficient (ICC) and Cohen's kappa coefficient (K) for ilium (ICC = 0.81, K = 0.56), os ischium (ICC = 0.89, K = 0.63) and femoral head (ICC = 0.83, K = 0.66), and moderate to good agreement for labrum (ICC = 0.65, K = 0.33). This new technique could ensure high scan quality and facilitate more widespread use of ultrasound in population screening of DDH.

Study of distributed suction of the boundary layer influencing the flow past a 3D roughness element on a straight wing model

Study of distributed suction of the boundary layer influencing the flow past a 3D roughness element on a straight wing model