Articoli di riviste: "Attack angle"

1

Yeston, J. "Angle of Attack". Science 337, n. 6096 (16 agosto 2012): 779. http://dx.doi.org/10.1126/science.337.6096.779-b.

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Brice, Jennifer. "Angle of Attack". River Teeth: A Journal of Nonfiction Narrative 6, n. 1 (2004): 17–40. http://dx.doi.org/10.1353/rvt.2005.0003.

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3

Jiang, Hai Bo, Yan Ru Li e Zhong Qing Cheng. "Relations of Lift and Drag Coefficients of Flow around Flat Plate". Applied Mechanics and Materials 518 (febbraio 2014): 161–64. http://dx.doi.org/10.4028/www.scientific.net/amm.518.161.

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In this paper, when Reynolds number is within the range of 10000 to 1000000, the horizontal component of the total pressure of flow around flat plate at high angle of attack was regarded as lift of high angle of attack, and the vertical component was regarded as drag of high angle of attack. The horizontal component of total pressure at small angle of attack was regarded as shape drag, and the total drag coefficient at small angle of attack was considered to the sum of the shape drag and frictional drag at zero angle of attack. For the two states of large and small angle of attack, the application scopes of the formulas of lift and drag coefficients were given. Final, the relations of lift and drag coefficients were obtained by eliminating all angles of attack. Research results show that lift - drag curve of small angles of attack is parabola, and the lift - drag curve of high angles of attack is circle.

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4

Gollomp, B. "The angle of attack". IEEE Instrumentation & Measurement Magazine 4, n. 1 (marzo 2001): 57–58. http://dx.doi.org/10.1109/5289.911179.

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Gatti-Bono, Caroline, e N. C. Perkins. "Effect of Loop Shape on the Drag-Induced Lift of Fly Line". Journal of Applied Mechanics 71, n. 5 (1 settembre 2004): 745–47. http://dx.doi.org/10.1115/1.1778414.

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This note explains why casting a loop with a positive angle of attack is advantageous in distance fly casting. Several loop shapes, one with a positive angle of attack, one with a negative angle of attack, and two symmetrical loops with zero angle of attack are studied. For each loop, we compute the vertical drag component, i.e., the “lift.” It is found that a loop with a positive angle of attack generates lift about four times larger than a symmetrical loop. Thus, loops with positive angles of attack stay “aerialized longer” which is consistent with observations made by (competition) distance fly casters.

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Sun, Yong, e Xing Sheng Li. "Determination of Attack Angle and Tilt Angle of a Cutting Pick". Advanced Materials Research 705 (giugno 2013): 415–18. http://dx.doi.org/10.4028/www.scientific.net/amr.705.415.

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Mechanical excavators play an important role in mining and construction. An excavation machine cuts rocks using its cutterhead which is normally composed of a large number of cutting picks. These picks are installed on a drum with certain attack angles, tilt angles and skew angles. These angles, especially attack and tilt angles, will affect the forces acting on individual picks and the cutterhead. To ensure the reliability and productivity of the excavation machine, these angles have to be kept in their optimal values. However, in manufacturing, these three types of angles cannot be set simultaneously. They have to be respectively set one after another. As a result, the angle which is set previously will be changed by the angles which are determined after it. Understanding the relationship between the values of the final angle and the designed angle is important for optimizing drum and pick design. This paper develops a formula for quantitatively analyzing this relationship, with the research scope limited to attack angle and tilt angle only as the first stage of the study.

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Tang, Hui, Yulong Lei, Xingzhong Li e Yao Fu. "Numerical investigation of the aerodynamic characteristics and attitude stability of a bio-inspired corrugated airfoil for MAV or UAV applications". Energies 12, n. 20 (22 ottobre 2019): 4021. http://dx.doi.org/10.3390/en12204021.

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In this study, two-dimensional (2D) and three-dimensional (3D) numerical calculations were conducted to investigate the aerodynamic characteristics, especially the unsteady aerodynamic characteristics and attitude stability of a bio-inspired corrugated airfoil compared with a smooth-surfaced airfoil (NACA2408 airfoil) at the chord Reynolds number of 4000 to explore the potential applications of non-traditional, corrugated dragonfly airfoils for micro air vehicles (MAVs) or micro-sized unmanned aerial vehicles (UAVs) designs. Two problem settings were applied to our numerical calculations. First, the airfoil was fixed at a constant angle of attack to analyze the aerodynamic characteristics and the hydrodynamic moment. Second, the angle of attack of airfoils was passively changed by the fluid force to analyze the attitude stability. The current numerical solver for the flow field around an unsteady rotating airfoil was validated against the published numerical data. It was confirmed that the corrugated airfoil performs (in terms of the lift-to-drag ratio) much better than the profiled NACA2408 airfoil at low Reynolds number R e = 4000 in low angle of attack range of 0 ∘ – 6 ∘ , and performs as well at the angle of attack of 6 ∘ or more. At these low angles of attack, the corrugated airfoil experiences an increase in the pressure drag and decrease in shear drag due to recirculation zones inside the cavities formed by the pleats. Furthermore, the increase in the lift for the corrugated airfoil is due to the negative pressure produced at the valleys. It was found that the lift and drag in the 2D numerical calculation are strong fluctuating at a high angle of attacks. However, in 3D simulation, especially for a 3D corrugated airfoil with unevenness in the spanwise direction, smaller fluctuations and the smaller average value in the lift and drag were obtained than the results in 2D calculations. It was found that a 3D wing with irregularities in the spanwise direction could promote three-dimensional flow and can suppress lift fluctuations even at high angles of attack. For the attitude stability, the corrugated airfoil is statically more unstable near the angle of attack of 0 ∘ , has a narrower static stable range of the angle of attack, and has a larger amplitude of fluctuations of the angle of attack compared with the profiled NACA2408 airfoil. Based on the Routh–Hurwitz stability criterion, it was confirmed that the control systems of the angle of attack passively changed by the fluid force for both two airfoils are unstable systems.

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Xu, Yihang, Shaosong Chen e Hang Zhou. "Analysis of the Magnus Moment Aerodynamic Characteristics of Rotating Missiles at High Altitudes". International Journal of Aerospace Engineering 2021 (12 aprile 2021): 1–13. http://dx.doi.org/10.1155/2021/6623510.

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The Magnus moment characteristics of rotating missiles with Mach numbers of 1.3 and 1.5 at different altitudes and angles of attack were numerically simulated based on the transition SST model. It was found that the Magnus moment direction of the missiles changed with the increase of the angle of attack. At a low altitude, with the increase of the angle of attack, the Magnus moment direction changed from positive to negative; however, at high altitudes, with the increase of the angle of attack, the Magnus moment direction changed from positive to negative and then again to positive. The Magnus force direction did not change with the change of the altitude and the angle of attack at low angles of attack; however, it changed with altitude at an angle of attack of 30°. When the angle of attack was 20°, the interference of the tail fin to the lateral force of the missile body was different from that for other angles of attack, leading to an increase of the lateral force of the rear part of the missile body. With the increasing altitude, the position of the boundary layer with a larger thickness of the missile body moved forward, making the lateral force distribution of the missile body even. Consequently, Magnus moments generated by different boundary layer thicknesses at the front and rear of the missile body decreased and the Magnus moment generated by the tail fin became larger. As lateral force directions of the missile body and the tail were opposite, the Magnus moment direction changed noticeably. Under a high angle of attack, the Magnus moment direction of the missile body changed with the increasing altitude. The absolute value of the pitch moment coefficient of the missile body decreased with the increasing altitude.

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9

Zhang, Li, Xinru Mao e Lin Ding. "Influence of attack angle on vortex-induced vibration and energy harvesting of two cylinders in side-by-side arrangement". Advances in Mechanical Engineering 11, n. 1 (gennaio 2019): 168781401882259. http://dx.doi.org/10.1177/1687814018822598.

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The vortex-induced vibration and energy harvesting of two cylinders in side-by-side arrangement with different attack angles are numerically investigated using two-dimensional unsteady Reynolds-Averaged Navier–Stokes simulations. The Reynolds number ranges from 1000 to 10,000, and the attack angle of free flow is varied from 0° to 90°. Results indicate that the vortex-induced vibration responses with attack angle range of 0°≤ α ≤ 30° are stronger than other attack angle cases. The parallel vortex streets are clearly observed with synchronized vortex shedding. Relatively large attack angle leads to a phase difference between the wake patterns of the two cylinders. Hydrokinetic energy can be obviously harvested when Re > 4000. Compared with the larger attack angle case, the two side-by-side cylinders with smaller attack angle have better performance on energy conversion. The maximum energy conversion efficiency of 21.7% is achieved. The optimum region for energy conversion is 5000 ≤ Re ≤ 7000 and 0°≤ α ≤ 30°.

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10

Popowski, Stanisław, e Witold Dąbrowski. "MEASUREMENT AND ESTIMATION OF THE ANGLE OF ATTACK AND THE ANGLE OF SIDESLIP". Aviation 19, n. 1 (30 marzo 2015): 19–24. http://dx.doi.org/10.3846/16487788.2015.1015293.

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The paper presents issues concerning the estimation of the angle of attack and the angle of sideslip on a flying object board. Angle of attack and sideslip estimation methods which are based on measurements of linear velocity components of an object with the Earth’s coordinates and on attitude angles of the object are presented. Both of these measurements originate from the inertial navigation system, and velocity measurement is obtained from the satellite navigation system. The idea of applying inertial and satellite navigation for the estimation of attack and sideslip angles is presented. Practical comparison of these estimation methods has been conducted based on logged parameters of a flight onboard a Mewa aircraft. Development proposals for these methods are presented as well.

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11

Xu, Zhijian, Guoming Zhang, Xiaoyu Ji e Wenyuan Xu. "Evaluation and defense of light commands attacks against voice controllable systems in smart cars". Noise & Vibration Worldwide 52, n. 4-5 (12 marzo 2021): 113–23. http://dx.doi.org/10.1177/09574565211001563.

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The in-car voice controllable system has become an almost standard feature in smart cars. Prior work shows that the voice controllable system is vulnerable to light commands attack which uses the laser as the medium to inject voice commands. In this article, we first reproduced the light commands attack on acoustic isolated in-car voice controllable system under several scenarios with a lightweight solution. We validate the feasibility of injecting the malicious voice command through a window into the microphone by modulating a laser beam. Then, we tested a variety of mainstream countermeasures such as placing sunscreen film on the glass panel to see whether it can protect the microphone from being attacked. Surprisingly, we find that the lower light transmittance of sunscreen film is the lower the success rate of the attack. Experiment results also show that when the transmittance rate of sun film is 50% which is the darkest sunscreen film that can be applied, the attacking success rate decreased by up to 0.4. We also explore the impact of attack angle by changing the incidence angle of the laser beam and the results demonstrate that light commands is sensitive to attack angle and the successful angle range is ± 15°. Finally, we propose a series of hardware-based protection schemes against light commands attacks.

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12

Erickson, G. E. "High Angle-of-Attack Aerodynamics". Annual Review of Fluid Mechanics 27, n. 1 (gennaio 1995): 45–88. http://dx.doi.org/10.1146/annurev.fl.27.010195.000401.

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13

Stollery, J. L. "High angle of attack aerodynamics". Journal of Atmospheric and Terrestrial Physics 54, n. 11-12 (novembre 1992): 1646. http://dx.doi.org/10.1016/0021-9169(92)90172-h.

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14

Li, Yang, Hao Zhou e Wanchun Chen. "Three-Dimensional Impact Time and Angle Control Guidance Based on MPSP". International Journal of Aerospace Engineering 2019 (24 febbraio 2019): 1–16. http://dx.doi.org/10.1155/2019/5631723.

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A new nonlinear guidance law for air-to-ground missile cooperation attacks is proposed in this paper. This guidance law enables missiles with different initial conditions to attack targets simultaneously, and it can also precisely satisfy the terminal impact angle conditions in both flight-path angle and heading angle. The guidance law is devised using the model predictive static programming (MPSP) method, and the control saturation constraint is incorporated in the MPSP algorithm. The first-order-lag acceleration of the missile is taken as the state variable to realize the convergence of the terminal acceleration to zero. Moreover, a collision avoidance strategy for three-dimensional missile cooperative flight is proposed. The simulation results show that the guidance law can make the missiles hit the target accurately at the same time with the ideal impact angles and can realize the control saturation constraints of the missiles. This can increase the attack effects and is significant for collaborative attacks.

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15

Hu, Haode, e Dongli Ma. "Airfoil Aerodynamics in Proximity to Wavy Ground for a Wide Range of Angles of Attack". Applied Sciences 10, n. 19 (27 settembre 2020): 6773. http://dx.doi.org/10.3390/app10196773.

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Wing-in-ground craft often encounter waves when flying over the sea surface, and the ground effect is more complicated than that of flat ground. Therefore, the aerodynamic characteristics of the NACA 4412 airfoil in proximity to wavy ground for a wide range of angles of attack is studied by solving the Reynolds Averaged Navier–Stokes equations. The validation of the numerical method is carried out by comparing it with the experimental data. The results show that the aerodynamic coefficients will fluctuate periodically when the airfoil moves over wavy ground at a small ride height. Except for the angle of attack of 0°, the fluctuation trend of aerodynamic coefficients at other angles of attack is the same. The analysis of aerodynamic fluctuation amplitude found that the medium angle of attack should be selected as the design cruise angle of attack for wing-in-ground craft. The time-averaged aerodynamic coefficients in the case of wavy ground are almost the same as those of flat ground. Hence, wavy ground mainly causes a fluctuation in aerodynamic coefficients. Considering the difference between aerodynamic coefficients at the angle of attack of 0° and at other angles of attack, the flow field structure at an angle of attack of 0° and 4° is analyzed. The results reveal the aerodynamic characteristics of the airfoil moving over wavy ground, which gives a deeper understanding of the ground effect in the conditions of wavy surface/ground. This has a certain guiding significance for the design of wing-in-ground craft.

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Zhao, Yuanyuan, Qiang Fu, Rongsheng Zhu, Guoyu Zhang, Chuan Wang e Xiuli Wang. "Transient Process and Micro-mechanism of Hydrofoil Cavitation Collapse". Processes 8, n. 11 (30 ottobre 2020): 1387. http://dx.doi.org/10.3390/pr8111387.

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Cavitation will cause abnormal flow, causing a series of problems such as vibration, noise, and erosion of solid surfaces. In severe cases, it may even destroy the entire system. Cavitation is a key problem to be solved for hydraulic machinery and underwater robots, and the attack angle is one of the most important factors affecting the cavitation. In order to systematically study the impact of the attack angle on the hydrofoil cavitation, the hydrofoils of NACA 4412 with different attack angles were selected to study the collapse process and hydraulic characteristics such as pressure, velocity, vortex, and turbulent kinetic energy during cavitation. The results showed that when the cavitation number was the same, the process of cavity collapse was greatly affected by the attack angle. The length of the cavity collapse area was positively correlated with the attack angle. As the attack angle increased, the volume of the falling bubbles increased, resulting in a larger pressure peak caused by the collapse of bubbles. Moreover, the pressure gradient near the collapse point changed more drastically, thereby affecting the growth of attached cavitation. The fluctuation range of vortex core and turbulent kinetic energy also increased with increasing the attack angle.

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Guo, Da Fei, Jian Xiang Xu e Ju Yuan. "Numerical Simulation on the Dynamic Stall of the Horizontal-Axis Wind Turbine". Applied Mechanics and Materials 448-453 (ottobre 2013): 1888–91. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.1888.

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With the variation of the unsteady incoming flow and impeller rotation, when attack angles of the incoming flow is bigger than the critical angle of attack, there are unsteady separation and dynamic stall on the pressure surface of the impeller. Dynamic stalls are of common occurrence during wind turbines operation. And the aerodynamic characteristics and efficiency of wind turbine are largely affected by the dynamic stall.Therefore,the study of dynamic stall has a great significance over the optimization design of the wind turbine. The paper performs numerical simulation in the dynamic stalls of the 1.2MW horizontal-axis wind turbine, comparing the stalling difference between two-dimensional static and rotating condition. Besides, it also contrasts the stalling condition surface pressure coefficient along the different blade spanwise sections in rotating condition of the same attack angle. And the finding is that the attack angles in rotating condition is bigger than that in the two-dimensional static condition; the surface pressure coefficient is almost equivalent in static and rotating condition when attack angle is smaller than stalling angle; the peak of negative pressure at the leading edge of blade in rotating condition is far bigger than the peak of negative pressure in static condition when attack angle is smaller than static stalling angle. Airflow stall delay occurs when near the blade root. Stall delay phenomenon gradually weakened along the direction of blade radius.

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18

Long, Wei, Zai Shuai Ling e Zhen Dang. "The Analysis about External Compressible Flow around an Aircraft Wing". Advanced Materials Research 1044-1045 (ottobre 2014): 654–58. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.654.

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The Steady flow simulation to selected the delta wing model for different angles of attack in the Maher number.The law of flow field changes with the angle of attack is gotten.Through the FLUENT simulation,The variation tendency of coefficient of lift and drag in the different angle of attack is gotten.Further reveals the change rule of Maher number, pressure, velocity and other parameters in the different angle of attack.With increasing angle of attack, Maher number distribution is sparse of the same position increases and the greater numerical.the distribution of velocity vector is sparse of the same position increases and the greater numerical.the pressure distribution is sparse of the same position increases and the greater numerical.

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19

Liu, Chuan-Zhen, e Peng Bai. "Nonlinear lift increase at high angles of attack for double swept waverider". International Journal of Modern Physics B 34, n. 14n16 (3 giugno 2020): 2040124. http://dx.doi.org/10.1142/s0217979220401244.

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The nonlinear increase of the lift of the double swept waverider at high angles of attack is of vital interest. The aerodynamic performance of the double swept waverider is calculated and compared with that of single swept waveriders. Results suggest that the lift nonlinearity of the double swept waverider is stronger than that of equal-planform-area single swept one, and the nonlinearity increases as Mach number increases. Some scholars have proposed the “vortex lift” to explain the nonlinear lift increase, but it is questionable as the main lift of the waverider comes from the lower surface rather than the upper surface. This paper proposes another explanation that the nonlinear lift increase is related to the attachment of shock wave, influenced by the leading-edge sweep angle. The shock wave is more inclined to attach under the lower surface with smaller swept than that of larger swept as angle of attack increases. When the shock wave attaches, the pressure increase via angle of attack is nonlinear, leading to the nonlinearity of lift increase.

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Krammer, Oliver, László Jakab, Balazs Illes, David Bušek e Ivana Beshajová Pelikánová. "Investigating the attack angle of squeegees with different geometries". Soldering & Surface Mount Technology 30, n. 2 (3 aprile 2018): 112–17. http://dx.doi.org/10.1108/ssmt-09-2017-0023.

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Purpose The attack angle of stencil printing squeegees with different geometries was analysed using finite element modelling. Design/methodology/approach A finite element model (FEM) was developed to determine the attack angle during the stencil printing. The material properties of the squeegee were included in the model according to the parameters of steel AISI 4340, and the model was validated by experimental measurements. Two geometric parameters were investigated; two different unloaded angles (45° and 60°) and four overhang sizes of the squeegee (6, 15, 20 and 25 mm). Findings It was found that the deflection of the blade is nearly homogenous along the length of the squeegee. This implies that the attack angle does not change significantly along the squeegee length. The results showed significant differences between the initial and the attack angle. For example, the angle of the squeegee with 15 mm overhang size and with 60° initial angle decreased by more than 5° for a specific squeegee force of 0.3 N/mm; resulting in an attack angle of 53.4°. Originality/value The attack angle during the printing is considerably lower than the initial angle as a result of the printing force. The papers, which were dealing with the numerical modelling of the stencil printing presumed that the squeegees were having their initial angle. This could have led to invalid numerical results. Therefore, we decided to investigate the attack angle during stencil printing for squeegees with different initial geometries to enhance the numerical modelling of stencil printing.

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FIGAT, Marcin, e Zdobysław GORAJ. "ANALYSIS OF STABILITY DERIVATIVES IMPORTANT TO RECOVERY FROM SPIN". Aviation 20, n. 2 (16 giugno 2016): 48–52. http://dx.doi.org/10.3846/16487788.2016.1195060.

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This paper describes the numerical analysis of light aircraft stability derivatives in a wide range of angles of attack, important for recovery from spin. Stability derivatives versus angle of attack and sideslip were calculated using a CFD software, based on Euler equation combined with boundary layer equations. The analysis was performed up to the 40 deg of angle of attack and up to 25 deg of sideslip.

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Anwar-ul-Haque, Ning Qin e Farooq Umar. "ASYMMETRY OF FLOW AT HIGH ANGLE OF ATTACK(Compressible Flow)". Proceedings of the International Conference on Jets, Wakes and Separated Flows (ICJWSF) 2005 (2005): 661–66. http://dx.doi.org/10.1299/jsmeicjwsf.2005.661.

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Cao, Yu Ji, Shi Ying Zhang e Peng Gao. "Investigation of Attack Angle Character for Hypersonic Inlet". Advanced Materials Research 468-471 (febbraio 2012): 1978–81. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.1978.

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The comparison analysis of performance with design point has been done in view of two different inlets, which were built by uniform shock intensity and shock angle method respectively. Base on this, the attack angle performance was emphatic developed on off-design point. The numerical calculation and analysis was conducted in eight different attack angle for air inlet conditions on two kinds of inlet respectively. The result indicated that, the inlet with uniform shock intensity method has 5% much more flow coefficient than inlet with uniform shock angle, in the condition of design point. In the condition of off-design point, the influence of the inlet performance is relatively small to the later kind of inlet with the increase of positive attack angel.

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Lacagnina, Giovanni, Paruchuri Chaitanya, Jung-Hoon Kim, Tim Berk, Phillip Joseph, Kwing-So Choi, Bharathram Ganapathisubramani et al. "Leading edge serrations for the reduction of aerofoil self-noise at low angle of attack, pre-stall and post-stall conditions". International Journal of Aeroacoustics 20, n. 1-2 (1 febbraio 2021): 130–56. http://dx.doi.org/10.1177/1475472x20978379.

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This paper addresses the usefulness of leading edge serrations for reducing aerofoil self-noise over a wide range of angles of attack. Different serration geometries are studied over a range of Reynolds number [Formula: see text]. Design guidelines are proposed that permit noise reductions over most angles of attack. It is shown that serration geometries reduces the noise but adversely effect the aerodynamic performance suggesting that a trade-off should be sought between these two considerations. The self-noise performance of leading edge serrations has been shown to fall into three angle of attack (AoA) regimes: low angles where the flow is mostly attached, moderate angles where the flow is partially to fully separated, and high angles of attack where the flow is fully separated. Leading edge serrations have been demonstrated to be effective in reducing noise at low and high angles of attack but ineffective at moderate angles. The noise reduction mechanisms are explored in each of three angle regimes.

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Baigang, Mi, e Yu Jingyi. "An Improved Nonlinear Aerodynamic Derivative Model of Aircraft at High Angles of Attack". International Journal of Aerospace Engineering 2021 (8 settembre 2021): 1–12. http://dx.doi.org/10.1155/2021/5815167.

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The classical aerodynamic derivative model is widely used in flight dynamics, but its application is extremely limited in cases with complicated nonlinear flows, especially at high angles of attack. A modified nonlinear aerodynamic derivative model for predicting unsteady aerodynamic forces and moments at a high angle of attack is developed in this study. We first extend the higher-order terms to describe the nonlinear characteristics and then introduce three more influence parameters, the initial angle of attack, the reduced frequency, and the oscillation amplitude, to correct the constant aerodynamic derivative terms that have higher-order polynomials for these values. The improved nonlinear aerodynamic derivative model was validated by using the NACA 0015 airfoil and the F-18 model. The results show that the improved model has a higher prediction ability at high angles of attack and has the ability to predict the aerodynamic characteristics of other unknown states based on known unsteady aerodynamic data, such as the initial angle of attack, reduced frequency, and oscillation amplitude.

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Zhao, Jie, Xiong Wei Liu, Lin Wang e Xin Zi Tang. "Design Attack Angle Analysis for Fixed-Pitch Variable-Speed Wind Turbine". Advanced Materials Research 512-515 (maggio 2012): 608–12. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.608.

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The purpose of this paper is to find the optimum design attack angle for fixed-pitch variable-speed wind turbine blade design, given the base-line wind turbine and the blade airfoil. Aerodynamic characteristics, i.e. lift and drag coefficients and lift to drag ratio, of the wind turbine, are analyzed. Two design attack angles along with the base-line attack angle (with maximum lift to drag ratio) are selected for the wind turbine blade design exercise. Blade design outcomes are analyzed and compared along with load performance and power performance. This paper is possibly the first attempt to determine the optimized design attack angle for maximizing annual energy production, given the base-line wind turbine and the blade airfoil.

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Dos Santos, Guilherme P., Adriano Kossoski, Jose M. Balthazar e Angelo Marcelo Tusset. "SDRE and LQR Controls Comparison Applied in High-Performance Aircraft in a Longitudinal Flight". International Journal of Robotics and Control Systems 1, n. 2 (26 maggio 2021): 131–44. http://dx.doi.org/10.31763/ijrcs.v1i2.329.

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This paper presents the design of the LQR (Linear Quadratic Regulator) and SDRE (State-Dependent Riccati Equation) controllers for the flight control of the F-8 Crusader aircraft considering the nonlinear model of longitudinal movement of the aircraft. Numerical results and analysis demonstrate that the designed controllers can lead to significant improvements in the aircraft's performance, ensuring stability in a large range of attack angle situations. When applied in flight conditions with an angle of attack above the stall situation and influenced by the gust model, it was demonstrated that the LQR and SDRE controllers were able to smooth the flight response maintaining conditions in balance for an angle of attack up to 56% above stall angle. However, for even more difficult situations, with angles of attack up to 76% above the stall angle, only the SDRE controller proved to be efficient and reliable in recovering the aircraft to its stable flight configuration.

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Harloff, Gary J. "High angle-of-attack hypersonic aerodynamics". Journal of Spacecraft and Rockets 25, n. 5 (settembre 1988): 343–44. http://dx.doi.org/10.2514/3.26010.

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Dexter, P. C. "High Angle of Attack Missile Aerodynamics". Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 207, n. 1 (gennaio 1993): 15–19. http://dx.doi.org/10.1243/pime_proc_1993_207_241_02.

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A major influence in the aerodynamics of missiles is the significant amount of separated flow encountered for most flight conditions. This flow may be of an ordered nature, forming vortices, or random, such as encountered in wing stall. At high angles of attack the vortices of the body leeside flow may become unpredictably asymmetric, even on geometrically symmetric configurations, and their interactions with wing and tail panels can result in possible control problems. The modelling of such flows both accurately and easily is beyond present capabilities.

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McDevitt, T. K., e F. K. Owen. "An optical angle of attack sensor". IEEE Aerospace and Electronic Systems Magazine 5, n. 2 (febbraio 1990): 19–27. http://dx.doi.org/10.1109/62.50842.

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31

Тлеулинов, М. К. "Бифуркация Пуанкаре-Андронова-Хопфа в колебаниях прощелкивания составных несущих и управляющих поверхностей летательных аппаратов". Письма в журнал технической физики 45, n. 15 (2019): 47. http://dx.doi.org/10.21883/pjtf.2019.15.48088.17656.

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Oscillations of a catastrophic change in shape (oscillations of clicking) compound lifting and control surfaces interconnected in a statically indefinable manner are considered. The influence of the angle of attack on the nature of oscillations is investigated. The phase portraits of the twisting angle of the control surface at different angles of attack are given.

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32

Xu, Fu You, Bin Bin Li, Cai Liang Huang e Zhe Zhang. "Experimental Research on Aerodynamic Characteristics of Bridge Deck at Extreme Attack Angles". Advanced Materials Research 163-167 (dicembre 2010): 4104–8. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.4104.

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Long-span flexible bridges are always challenged by fierce wind load, and the wind with extreme-attack-angle may be a potential danger to threaten the bridge security. The three-component coefficients at extreme attack angles of the section model of one flat streamlined box-girder and central slotted box-girder are investigated through the wind tunnel test, and the detailed explanation are made. The results show that lift and pitch coefficients change approximately linearly between stall angles, and the coefficients display significant nonlinearity and a certain pulsation phenomenon when the attack angle exceeds stall angles, and the stall angles should not be less than ±10° for the sake of the safety of bridges.

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33

Kadhem, Hassan Ali, e Ahmed Abdul Hussein. "The Effect of Attack Angle On The Vibration Suppression Of Composite Wing Airfoil NACA 0012". Association of Arab Universities Journal of Engineering Sciences 27, n. 4 (3 gennaio 2021): 17–21. http://dx.doi.org/10.33261/https://doi.org/10.33261/jaaru.2020.27.4.003.

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Active vibration control is presented as an effective technique used for vibration suppression and for attenuating bad effects of disturbances on structure. In this work Proportional-Integral-Derivative control were employed to study suppression of active vibration wing affected by wind airflow. Two different composite wings with different manufacturing materials had been made with specific size to be suitable for using in wind tunnel. Piezoelectric (PZT (transducers are used as sensors and actuators in vibration control systems. The velocity was 25 m/s and three different attack angles (0, 10, 20 degrees) had been taken to show their effect on the wings vibrations suppression. The results shows that the suppression of the wing amplitude is reduced when the attack angle increases for both woven and random composite wing matt and this happened due to the vortex which became more violent at the increase of attack angle and also due to the area that face the wind which will increase when the attack angle increase and this will reduces the suppression. The maximum control amplitude of woven Glass-fiber matt was 1.75cm and the damping was about 38 % at zero attack angle while it was 2cm and the damping was about 26 % at 20 degree attack angle for random Glass-fiber composite matt

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34

Ko, Arim, Kyoungsik Chang, Dong-Jin Sheen, Young-Hee Jo e Ho Joon Shim. "CFD Analysis of the Sideslip Angle Effect around a BWB Type Configuration". International Journal of Aerospace Engineering 2019 (23 aprile 2019): 1–14. http://dx.doi.org/10.1155/2019/4959265.

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In this study, we conducted numerical simulations for a nonslender BWB type planform with a rounded leading edge and span of 2.0 m to analyze the effect of the sideslip angle on the planform at a freestream velocity of 60 m/s. The Reynolds number based on the mean chord length was 2.9×106, and we considered the angle of attack ranging from -4° to 16° and sideslip angles up to 20°. We used an unstructured mesh with a prism layer for the boundary layer with 1.11×107 grid points, and the k−ω SST turbulence model. We analyzed force and moment coefficients with respect to variation of angle of attack and sideslip angles. Side force and rolling/yawing moment coefficients had highly nonlinear relationships with the sideslip angle while lift and drag coefficients were not significantly affected. We interpreted the mechanism of these aerodynamic characteristics based on pressure and skin friction contours. Suction pressure near the leading edge had a marked effect on the pitching and rolling moment. We identified five flow types on the blunt leading edge swept wing by skin friction lines and off-body streamlines at a high angle of attack and sideslip angles.

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35

Kato, K., K. Hokkirigawa, T. Kayaba e Y. Endo. "Three Dimensional Shape Effect on Abrasive Wear". Journal of Tribology 108, n. 3 (1 luglio 1986): 346–49. http://dx.doi.org/10.1115/1.3261193.

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The three dimensional shape effect of asperity on abrasive wear was investigated with in-situ experiments in the scanning electron microscope. The geometry of model asperity was represented by attack angle and dihedral angle, where attack angle changed in 0∼90 deg and dihedral angle in 0∼180 deg. Wear modes of shearing, cutting, and wedge forming were observed and each mode was related to attack angle and dihedral angle by wear mode diagram. Wear rate in cutting mode increased with attack angle and was maximum at a certain dihedral angle.

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36

Mahdi, Mohammed, e Yasser A. Elhassan. "Stability Analysis of a Light Aircraft Configuration Using Computational Fluid Dynamics". Applied Mechanics and Materials 225 (novembre 2012): 391–96. http://dx.doi.org/10.4028/www.scientific.net/amm.225.391.

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This work aims to simulate and study the flow field around SAFAT-01 aircraft using numerical solution based on solving Reynolds Averaged Navier-Stokes equations coupled with K-ω SST turbulent model. The aerodynamics behavior of SAFAT-01 aircraft developed at SAFAT aviation complex were calculated at different angles of attack and side slip angles. The x,y and z forces and moments were calculated at flight speed 50m/s and at sea level condition. Lift and drag curves for different angles of attack were plotted. The maximum lift coefficient for SAFAT-01 was 1.67 which occurred at angle of attack 16° and Maximum lift to drag ratio (L/D) was 14 which occurred at α=3°, and the zero lift drag coefficient was 0.0342. Also the yawing moment coefficient was plotted for different side slip angles as well as rolling moment. The longitudinal stability derivatives with respect to angle of attack, speed variation (u), rate of pitch (q) and time rate of change of angle of attack were calculated using obtained CFD results. Concerning lateral stability only side slips derivatives were calculated. To validate this numerical simulation USAF Digital DATCOM is used to analyze this aircraft; a comparison between predicted results for this aircraft and Digital DATCOM indicated that this numerical simulation has high ability for predicting the aerodynamics characteristics.

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37

Motwani, D. G., U. N. Gaitonde e S. P. Sukhatme. "Heat Transfer From Rectangular Plates Inclined at Different Angles of Attack and Yaw to an Air Stream". Journal of Heat Transfer 107, n. 2 (1 maggio 1985): 307–12. http://dx.doi.org/10.1115/1.3247415.

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Average heat transfer coefficients during forced convection air flow over inclined and yawed rectangular plates have been experimentally determined. Tripping wires at the edges ensured that a turbulent boundary layer prevailed over the plates. The experiments were carried out for a constant surface temperature and covered two plates of different aspect ratios, angles of attack from 0 to 45 deg, angles of yaw from 0 to 30 deg, and Reynolds numbers from 2 times; 104 to 3.5 times; 105. The results show that the average heat transfer coefficient is essentially insensitive to the aspect ratio and angle of yaw. However, it is a function of Reynolds number and the angle of attack. Correlation equations for various angles of attack are suggested.

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38

Lam, K., Y. F. Lin, Y. Liu e L. Zou. "Numerical Investigation of Flow past a Wavy Airfoil". Applied Mechanics and Materials 110-116 (ottobre 2011): 4269–75. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.4269.

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The effect of the wavy surface on the aerodynamic characteristics of an airfoil is studied using the large eddy simulations. A more gentle lift characteristic is obtained during stall. For angles of attack less than the baseline stall angle of a NACA0012 airfoil, a lift coefficient reduction was observed for the wavy airfoils, while the lift coefficient increases up to 23% greater than that of a NACA0012 airfoil when the angle of attack is larger than the baseline stall angle of the NACA0012 airfoil.

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39

Koide, S. "Prediction of Separation Angles Induced by Sharp Fins with Attack Angle". AIAA Journal 39, n. 11 (novembre 2001): 2223–25. http://dx.doi.org/10.2514/2.1223.

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40

Koide, S. "Prediction of separation angles induced by sharp fins with attack angle". AIAA Journal 39 (gennaio 2001): 2223–25. http://dx.doi.org/10.2514/3.14990.

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41

Chakrabarty, Dipes, e Ranajit Brahma. "Effect of wall proximity in fluid flow and heat transfer from a square prism placed inside a wind tunnel". Thermal Science 11, n. 4 (2007): 65–78. http://dx.doi.org/10.2298/tsci0704065c.

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Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due to flow separation around square prisms. Experiments have been carried out for the Reynolds number 4.9?104, blockage ratios are 0.1, 0.2, 0.3 and 0.4, different height-ratios, and various angles of attack. The static pressure distribution has been measured on all faces of the square prisms. The results have been presented in the form of pressure coefficient, drag coefficient for various height-ratios and blockage ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body approaches towards the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack as the height-ratio decreases. The maximum value of drag coefficient has been observed at an angle of attack nearly 50? for square prism at all height-ratios. The heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficients are determined from the measured wall temperature and ambient temperature, and presented in the form of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of local Nusselt number has been shown with non-dimensional distance for different angles of attack and blockage ratios. The variation of average Nusselt number has also been shown with different angles of attack for blockage ratios. The local as well as average Nusselt number decreases as the height-ratio decreases for all non-dimensional distance and angle of attack for square prisms. The average Nusselt number for square prisms of different blockage ratio varies with the angle of attack. But there is no definite angle of attack at different block- age ratio at which the value of average Nusselt number is either maximum or minimum.

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42

ElAwad, Yasir A., e Eltayeb M. ElJack. "Numerical investigation of the low-frequency flow oscillation over a NACA-0012 aerofoil at the inception of stall". International Journal of Micro Air Vehicles 11 (gennaio 2019): 175682931983368. http://dx.doi.org/10.1177/1756829319833687.

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High-fidelity large eddy simulation is carried out for the flow field around a NACA-0012 aerofoil at Reynolds number of [Formula: see text], Mach number of 0.4, and various angles of attack around the onset of stall. The laminar separation bubble is formed on the suction surface of the aerofoil and is constituted by the reattached shear layer. At these conditions, the laminar separation bubble is unstable and switches between a short bubble and an open bubble. The instability of the laminar separation bubble triggers a low-frequency flow oscillation. The aerodynamic coefficients oscillate accordingly at a low frequency. The lift and the drag coefficients compare very well to recent high-accuracy experimental data, and the lift leads the drag by a phase shift of [Formula: see text]. The mean lift coefficient peaks at the angle of attack of [Formula: see text], in total agreement with the experimental data. The spectra of the lift coefficient does not show a significant low-frequency peak at angles of attack lower than or equal the stall angle of attack ([Formula: see text]). At higher angles of attack, the spectra show two low-frequency peaks and the low-frequency flow oscillation is fully developed at the angle of attack of [Formula: see text]. The behaviour of the flow-field and changes in the turbulent kinetic energy over one low-frequency flow oscillation cycle are described qualitatively.

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43

Schettini, Francesco, Gianpietro Di Rito e Eugenio Denti. "Aircraft flow angles calibration via observed-based wind estimation". Aircraft Engineering and Aerospace Technology 91, n. 7 (8 luglio 2019): 1033–38. http://dx.doi.org/10.1108/aeat-06-2017-0145.

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Purpose This paper aims to propose a novel approach, in which the reference data for the flow angles calibration are obtained by using measurements coming from an inertial navigation system and an air data sensor. Design/methodology/approach This is obtained by using the Kalman filter theory for the evaluation of the reference angle-of-attack and angle-of-sideslip. Findings The designed Kalman filter has been implemented in Matlab/Simulink and validated using flight data coming from two very different aircraft, the Piaggio Aerospace P1HH medium altitude long endurance unmanned aerial system and the Alenia-Aermacchi M346 Master™ transonic trainer. This paper illustrates some results where the filter satisfactory behaviour is verified by comparing the filter outputs with the data coming from high-accuracy nose-boom vanes. Practical implications The methodology aims to lower the calibration costs of the air data systems of an advanced aircraft. Originality/value The calibration of air-data systems for the evaluation of the flow angles is based on the availability of high-accuracy reference measurements of angle-of-attack and angle-of-sideslip. Typically, these are obtained by auxiliary sensors directly providing the reference angles (e.g. nose-boom vanes). The proposed methodology evaluates the reference angle-of-attack and angle-of-sideslip by analytically reconstructing them using calibrated airspeed measurements and inertial data.

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44

Haese, P. M. "Cavities at atmospheric pressure behind two-dimensional bodies at an angle of attack". ANZIAM Journal 47, n. 1 (luglio 2005): 103–19. http://dx.doi.org/10.1017/s1446181100009809.

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AbstractThis paper presents an interior source method for the calculation of semi-infinite cavities behind two-dimensional bluff bodies placed at an angle of attack in a uniform stream. Aspects under consideration include the pressure distribution along the body, especially just ahead of the separation point, lift and drag forces, and how these quantities vary with the angle of attack. We include discussion of the physical conditions of separation, and identify critical angles of attack for which the cavitating flow past an airfoil may (a) become unstable, or (b) yield the greatest lift to drag ratio.

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45

Ali, Zurriati Mohd, Wahyu Kuntjoro e Wisnoe Wirachman. "The Effect of Canard to the Aerodynamic Behavior of Blended Wing Body Aircraft". Applied Mechanics and Materials 225 (novembre 2012): 38–42. http://dx.doi.org/10.4028/www.scientific.net/amm.225.38.

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This paper presents a study on the effect of canard setting angle on the aerodynamic characteristic of a Blended Wing Body (BWB). Canard effects to BWB aerodynamic characteristics are not widely investigated. Hence the focus of the study is to investigate the variations of lifts, drags and moments when the angles of attack are varied at different canard setting angles. Wind tunnel tests were performed on BWB aircraft with canard setting angles,  ranging from -20˚ to 20˚. Angles of attack,  were varied from -10˚ to 10˚. Aspect ratio and canard planform area were kept fixed. All tests were conducted in the subsonic wind tunnel at Universiti Teknologi MARA, at Mach number of 0.1. The streamlines flow, at the upper surface of the canard was visualized using mini tuft. Result shows that the lift coefficient does not change much with different canard setting angles. As expected, the lift coefficient increases with increasing angles of attack at any canard setting angle. In general, the moment coefficient increases as the canard setting angle is increased. The results obtained in this research will be of importance to the understanding of aerodynamic behavior of BWB employing canard in its configuration.

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46

Yocum, A. M., e W. F. O’Brien. "Separated Flow in a Low-Speed Two-Dimensional Cascade: Part II—Cascade Performance". Journal of Turbomachinery 115, n. 3 (1 luglio 1993): 421–34. http://dx.doi.org/10.1115/1.2929269.

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This study was conducted for the purpose of providing a more fundamental understanding of separated flow in cascades and to provide performance data for fully stalled blade rows. Cascades of a single blade geometry and a solidity of unity were studied for three stagger angles and the full range of angle of attack extending well into the stalled flow regime. The Reynolds number was also varied for a limited number of cases. Results from velocity and pressure measurements made in the cascade and the overall cascade performance evaluated from these measurements are presented. In addition, results from a numerical simulation of the flow through a cascade of flat plate airfoils are used to illustrate further the effects of blade stagger and to define the correct limits for the cascade performance. The results indicate that the slope of the total pressure loss versus angle of attack curve for the flow immediately downstream of the cascade is steeper for cascades with greater stagger. The normal force coefficient was found to increase to a peak value near the angle of attack where full leading edge stall first occurs. A further increase in angle of attack results in a decline in the normal force coefficient. The peak value of the normal force coefficient is greater and occurs at a higher angle of attack for the cascades with smaller stagger.

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47

Huang, Yuqi, James Venning, Mark C. Thompson e John Sheridan. "Vortex separation and interaction in the wake of inclined trapezoidal plates". Journal of Fluid Mechanics 771 (20 aprile 2015): 341–69. http://dx.doi.org/10.1017/jfm.2015.160.

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Full three-dimensional numerical simulations are employed to investigate the flows over inclined trapezoidal low-aspect-ratio plates at low Reynolds numbers, aiming to understand the unsteadiness induced by the interaction between the trailing vortical wake structures originating from the swept edges, and those from the leading and trailing edges. The flows past eighteen different plate geometries in three broad sets are simulated to study the influence of aspect ratio, taper angle and angle of attack on the wake vortices and the force coefficients. Both taper ratio and angle of attack of plates with the same area are found to have a broadly predictable influence on the wake stability and asymptotic forces. Smaller taper ratios result in lower maximum lift, while an increase in the angle of attack results in a reduction in the differences in maximum lift. Two distinct modes of periodic unsteady flow with significant differences in frequency are observed. The corresponding vortex-shedding mechanisms are analysed with the aid of $Q$-criterion isosurfaces and streamlines. A low wake frequency is observed at small taper angles when there is relative independence between the von Kármán vortices originating from the leading and trailing edges, and weak swept-edge vortices. The dominant Strouhal number in this state is approximately 0.09. When the taper angle or angle of attack increases, the flows over the swept edges form stronger trailing vortex structures which interact strongly with the leading-edge vortices, combining to produce a regular stream of vortex loops shed into the wake. In this regime, the dominant Strouhal number increases to approximately 0.14–0.18. Higher Reynolds numbers and/or angles of attack result in a loss of centre plane reflection symmetry in the wake. The aerodynamic forces have been quantified as a function of the problem parameters and plate geometry.

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48

Valasek, John, Joshua Harris, Shawn Pruchnicki, Matthew McCrink, James Gregory e David G. Sizoo. "Derived Angle of Attack and Sideslip Angle Characterization for General Aviation". Journal of Guidance, Control, and Dynamics 43, n. 6 (giugno 2020): 1039–55. http://dx.doi.org/10.2514/1.g004010.

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49

Shendge, Smit. "Study and Design a Spoiler to Understand Aerodynamics with Various Angle of Attack at Different speeds". International Journal for Research in Applied Science and Engineering Technology 9, n. 8 (31 agosto 2021): 2648–56. http://dx.doi.org/10.22214/ijraset.2021.37787.

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Abstract: In this scope of study, various type of spoiler is researched out of which a pedestal spoiler is chosen to design as it generates a very good downforce and also has good aesthetic appeal to it, spoiler is designed considering actual scaled dimensions. Analysis on the designed pedestal spoiler is carried out to get to know how much the downforce is generated and at the same time how much drag coefficient is produced. Also, angle of attack of the spoiler in various degrees (9, 6, 4, 3, 2, 0, -2, - 3, -4, -6, -9, -12, -15) is carried out to know downforce at various angle of attack with various velocity (10, 15, 20, 25, 30, 35, 40, 45, 50) inputs in meter per seconds. After carrying out more than 80 analysis, found that highest downforce generated by the spoiler’s angle of attack is at (-6) degree with a 400 N of downforce and also with low drag. Velocity magnitude contour plot of each angle is provided to understand the air flow around each angle of attack. To validate the results given by the simulation tool a mathematical/analytical calculation are carried out for four angles of attack with a good result and also graphs are plotted for each validation to figure out the variation in them. Observing the validation’s graphs and calculations the difference between computational results and mathematical/analytical results is less than 5% indicating a proper process carried out in simulation and approximately giving realistic values that can be given in a wind tunnel aerodynamic test. Keywords: Spoiler, Aerodynamics, CAD, CFD, Drag coefficient, Lift coefficient, angle of attack.

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50

Kurtulus, Dilek Funda. "Unsteady aerodynamics of a pitching NACA 0012 airfoil at low Reynolds number". International Journal of Micro Air Vehicles 11 (gennaio 2019): 175682931989060. http://dx.doi.org/10.1177/1756829319890609.

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The present paper aims to investigate numerically small amplitude oscillation of NACA 0012 airfoil at Re = 1000. The airfoil is sinusoidally pitching around the quarter chord point with 1° pitch amplitude about a mean angle of attack. The computations are performed for mean angles of attack ranging from 0° to 60° and for pitching frequencies of 1 Hz and 4 Hz. The effect of the mean angle of attack and pitching frequency on the instantaneous forces as well as the vortex structure is investigated in comparison with the non-oscillatory conditions. It was shown that airfoil oscillations at the investigated conditions change the amplitude of oscillation of the aerodynamic loads. The instantaneous drag coefficient is always positive for pitching airfoil at 1 Hz. In the meantime, there are time intervals where instantaneous drag coefficient becomes negative for pitching motion at 4 Hz for mean angles of attack from 3° to 36°.

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