Angle Of Attack Range Research Articles

Influence of camber on aerodynamic performance of airfoil based on CFD technology

In order to better understand the influence of camber on aerodynamic performance of airfoil, airfoil NACA0012, NACA2412, NACA4412 and NACA6412 were selected as research objects to conduct numerical simulation at 10m/s. According to lift coefficient, lift-drag ratio and airfoil pressure cloud diagram, the influence of camber on airfoil aerodynamic performance is obtained. The results show that the lift coefficient of airfoil increases with the increase of airfoil bending degree within a certain range of attack Angle. The lift-drag ratio of airfoil increases with the increase of its bending degree.

Simulation of the Wheel-Surface Interaction Dynamics for All-Terrain Vehicles

In this paper, a new methodology for the numerical simulation of the wheel–surface interaction has been presented. The finite-element method was combined with the discrete-element method, rigid body dynamics, and the advanced wheel–surface friction model. Compared to the current state-of-the-art, this novel approach can more realistically model the application of the traction force on the contact surface between the wheel and the soil. The rotation of a non-driven wheel is caused by the movement of the axis and the contact forces. The method that has been developed is able to assess both the longitudinal and lateral forces for a wide range of attack angles of the wheel; this is essential for calculating the traction effort of skid-steered vehicles.

Analysis of Influence of Different Parameters on Numerical Simulation of NACA0012 Incompressible External Flow Field under High Reynolds Numbers

Currently, influence analysis of simulation parameters, especially the trailing edge shape and the corresponding modeling method on the force coefficients of NACA0012 under a high Reynolds number, is relatively sparse. In this paper, two trailing edge shapes are designed by three modeling methods and combined with three far-field distances to establish eighteen two-dimensional external flow fields. The same number of structured grids are generated by a unified grid strategy and the SST k-omega and the Spalart–Allmaras models are adopted to solve the NS equations to realize the numerical simulations. Unlike under low Reynolds numbers, the analysis results show that although the accuracy difference between the sharp trailing edge and the blunt trailing edge decreases as the attack angle range increases, the former is preferred in all studied ranges. As to the corresponding modeling methods, the NACA4 and the definition formula are preferred, the choice of which depends on the studied range. In particular, a greater number of data points adopted into the definition formula is not necessarily better. Considering the error ratios comprehensively, the simulation configurations of sharp trailing edge + 20 m far-field distance + SA/SST/SST/SST/SST/SA turbulence model obtains optimal simulation effects.

CFD analysis on the influence of angle of attack on vertical axis wind turbine aerodynamics

The Angle of Attack (AOA) in a Vertical Axis Wind Turbine (VAWT) plays an important role in determining the forces and the power generated by the wind turbine. It is difficult to find the suitable AOA due to the complex and constantly changing wind flow patterns. In this paper, we have performed CFD simulations using Ansys Fluent software, based on the constantly changing AOA. The CFD simulations were conducted by selecting a suitable range of AOA and the velocity of the wind. The selected range of AOA varied from 5 degrees to 25 degrees with increments of 5 degrees and the range of the air velocities varied from 7m/s to 21m/s with increments of 7m/s. The tests were also performed using the X-Foil software. The results obtained from the CFD simulations, done by using the Ansys Fluent Software and from the X-Foil software, were then compared to give a more accurate and optimized AOA and velocity value. This optimization of the AOA could enhance the overall performance of the Vertical Axis Wind turbine.

Studies Based on CFD Behaviour of Aerofoil and Regression Analysis

The performance of an aerofoil depends upon the angle of attack, leading-edge radius, surface modifications, etc. The aerofoil which has a broader range of attack angle and surface area is responsible for the upliftment in the performance of the aerofoil. The present work deals with the evaluation of the aerofoil spread with dimples over the active surface. The positions and area of spread are modified accordingly and evaluated for the velocity and pressure lineation. The aerofoil with 30% dimples over the active surface is found to possess higher values for the required intents of velocity and pressure at an inlet velocity of 9 m/s. The optimum model with better lineation values is further evaluated for the co-efficient of lift and drag to propose the best design. The best result is obtained at an aerofoil of NACA 8412 series with 30% dimples extension at the rear end placed at 15° angle of attack and the regression analysis is done for the coefficient of lift values.

Вплив пропорцій орбітальних об’єктів простої форми на їхні аеродинамічні характеристики

When developing modern and promising aerospace technology models, the relevance of simulation of the flow around apparatuses (spacecraft) of various geometric shapes in a transitional mode corresponding to the flight in the region of the upper layers of the atmosphere and near space is growing. Solving the Boltzmann equation, which most adequately describes this process in the framework of kinetic theory, still remains a difficult task. To solve this equation, the Monte Carlo statistical methods are used quite successfully. An example of such a method is the direct statistical simulation, or, less common but also well-established in rarefied gas dynamics, the test particles method (TPM). The aim of this work is to study the effect of geometric proportions of simply-shaped orbiting objects during uncontrolled descent to dense layers of the atmosphere on their drag coefficients. Such objects may be elements of space debris or spacecraft of appropriate shapes and proportions. The studies were based on the results obtained by numerical simulation of TPMs on uniform rectangular grids. The shape of the orbital objects was set in the form of a circular cone, cylinder, rectangular parallelepiped of various elongations, and spheres. The calculations were carried out in a wide range of attack angles. The characteristic dimensions of the body class in question varied from 2 to 12 meters. According to the standard atmosphere for such characteristic dimensions, the transitional flow regime is realized at altitudes from 90 km to 180 km. It was found that the calculated values of the drag coefficients in the transition regime are in satisfactory agreement with the experimental data and calculations on the theory of local interaction, and at an altitude of 300 km, they correspond to the control free molecular values obtained by analytical formulas. The dependence of the drag coefficients of the bodies of the considered shapes on the angle of attack and flight altitude was studied. The influence of the choice of the characteristic area on the range of values of the calculation results is shown. The drag coefficient of the considered class of bodies at the entrance to the dense layers of the atmosphere using the TPM was calculated for the first time. Satisfactory agreement of the obtained results with the available experimental and calculated data confirms the effectiveness of the applied method in transition mode. This makes it possible to use it in practical calculations of the parameters of the external environment effect on the spacecraft in the most difficult to study altitude ranges corresponding to the transitional flow regime.

공기역학적 불확실성을 고려한 CX 팬터그래프의 접촉력 안정성 평가

The stability of the contact force of CX pantograph was assessed with considering aerodynamic uncertainties of the angle of attack(AOA) and velocity of the inflow(V<SUB>i</SUB>). At first, the aerodynamic modeling of pan head of CX pantograph was performed. And the standard deviation of the contact force of the simulation results were calculated with changing AOA and V<SUB>i</SUB>; the range of AOA was from –10° to 10° at intervals of 2° and that of V<SUB>i</SUB> was from 200㎞/h to 400㎞/h at intervals of 50㎞/h. From the results, the response surface model was constructed using the 8<SUP>th</SUP> order regression equation. Then, Monte Carlo Simulation (MCS) was performed to assess the probabilitic charateristics of uncertainties of AOA and V<SUB>i</SUB>. Therefore, it became possible to statistically evaluate the change in contact force due to the aerodynamic uncertainties of the AOA and V<SUB>i</SUB>.

Experimental Determination of the Impact of Floats on the Aerodynamic Characteristics of an OSA Model in Symmetric Flow

This paper presents the results of experimental determination of the impact of floats on the aerodynamic characteristics of an OSA model in symmetric flow. The studies have been performed in the low-speed wind tunnel at the Military University of Technology (MUT, Warsaw, Poland). The aircraft model was examined at the dynamic pressure q = 500 Pa in the following angle of attack range = -2828. The investigations have been performed for an aircraft model under plain configuration with floats and without floats. The influence of elevator and flap inclination on the aerodynamic characteristics of the model has also been analysed. The obtained values of aerodynamic drag coefficient, lift coefficient, pitching moment coefficient and lift-to-drag ratio have been presented in the form of tables and graphs. The studies performed demonstrated that the use of floats causes the increase of aerodynamic drag coefficient CD, maximum lift coefficient CLmax as well as critical angle of attack cr. The decrease of lift-to-drag ratio has also been observed. Its value in the case of the model with floats was up to 20% lower than in the model without floats. The studies also showed that the model equipped with floats had a lower longitudinal static stability margin than the model without floats.

Numerical Investigation of the Effect of Changing the Thickness of Airfoils used in Wind Turbines on the Lift to Drag Ratio

In this paper, the effect of changing the thickness of the airfoils on the lift and drag coefficients and lift to drag ratio for three types of airfoils is presented. The study was done by making a 2D simulation by using the commercial software ANSYS FLUENT 2019R1. The airfoils that were selected for the simulation were the NREL S830, SG6043, and SD7062. In order to study the effect of changing the thickness of airfoils on the aerodynamic characteristics, the thickness of NREL S830, SG6043, and SD7062 airfoils was increased and decreased by 20%. The method used to increase and decrease the thickness was done by modifying the coordinates of the upper and lower curves of the baseline airfoils in the y-direction. The simulation was done using the Spalart Allmaras turbulence model for low wind speed (5m/s) and a wide range of attack angles (from 0 to 15 degrees). The aerodynamic characteristics, which are the lift and drag coefficients, lift to drag ratio, and the optimum angle of attack, are presented in this study. It was concluded that reducing the thickness to 20% leads to a remarkable increase in the lift to drag ratio while increasing the thickness leads to a decrease in the lift to drag ratio. It was also concluded that reducing thickness will not always lead to maximizing the lift coefficient but will always reduce the drag coefficient. It was also found that for wind turbines operating in low wind speed regions, the SG6043 airfoil profile is the most suitable as it showed a good aerodynamic performance at low wind speed.

Calibration of Reanalysis Data against Wind Measurements for Energy Production Estimation of Building Integrated Savonius-Type Wind Turbine

In this work, a cost-effective wind resource method specifically developed for the ROSEO-BIWT (Building Integrated Wind Turbine) and other Building Integrated Wind Turbines is presented. It predicts the wind speed and direction at the roof of an previously selected building for the past 10 years using reanalysis data and wind measurements taken over a year. To do so, the reanalysis wind speed data is calibrated against the measurements using different kinds of quantile mapping, and the wind direction is predicted using random forest. A mock-up of a building and a BIWT were used in a wind tunnel to perform a small-scale experiment presented here. It showed that energy production is possible and even enhanced over a wide range of attack angles. The energy production estimations made with the best performing kind of calibration achieved an overall relative error of 6.77% across different scenarios.

An angle-of-attack correction method for a 2-D miniature differential pressure solid-state anemometer

Differential pressure solid-state anemometers are suitable for mobile meteorological monitoring because of their small size, high precision, and firmness. However, they suffer from large angle-of-attack (AOA) errors caused by tilts in mobile meteorological monitoring applications. To compensate for these errors, an AOA correction method is presented on the basis of theoretical analysis and CFD (computational fluid dynamics) simulation. The model is tested and verified in a wind tunnel. The anemometer can accurately measure the wind parameters with a speed error of less than 5% and a direction error within ± 5° in the AOA range of 0° to 45°.

A study on the hydrodynamic performance of manta ray biomimetic glider under unconstrained six-DOF motion.

A manta ray biomimetic glider is designed and studied with both laboratory experiments and numerical simulations with a new dynamic update method called the motion-based zonal mesh update method (MBZMU method) to reveal its hydrodynamic performance. Regarding the experimental study, an ejection gliding experiment is conducted for qualitative verification, and a hydrostatic free-fall experiment is conducted to quantitatively verify the reliability of the corresponding numerical simulation. Regarding the numerical simulation, to reduce the trend of nose-up movement and to obtain a long lasting and stable gliding motion, a series of cases with the center of mass offset forward by different distances and different initial angles of attack have been calculated. The results show that the glider will show the optimal gliding performance when the center of mass is 20mm in front of the center of geometry and the initial attack angle range lies between A0 = -5° to A0 = -2.5° at the same time. The optimal gliding distance can reach six times its body length under these circumstances. Furthermore, the stability of the glider is explained from the perspective of Blended-Wing-Body (BWB) configuration.

Low speed lateral-directional dynamic stability analysis of a hypersonic waverider using unsteady Reynolds averaged Navier Stokes forced oscillation simulations

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes have been confined to static investigations, with limited work on longitudinal dynamics. No studies outlining the lateral-directional dynamic stability and aerodynamic derivatives has ever been published. This paper presents results for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider, which was subjected to forced oscillations in roll, yaw and side-to-side translations. This was achieved using unsteady Reynolds Averaged Navier Stokes simulations. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately 1.5×106. The dynamic motion was at a forced frequency of 1 Hz with angle amplitudes of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the nominal centre of gravity location at 44.4% of the vehicle length show values for the dynamic derivatives within expected ranges, apart from the rolling moment due to yaw rate below approximately 2 degrees angle of attack. A similar finding for the dihedral derivative in static tests concluded that the low mounted wing with anhedral results in instabilities at low angles of attack. Investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed data within normal ranges. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. Some significant impact was seen on the roll damping derivative due to lowering the centre of gravity. This is from a combination of non-linear wing side force variance with angle of attack and the reduction of the moment arm, which resulted in less damping. The derivatives generally showed little sensitivity to changes in the oscillation frequency, with frequency rates ranging from 0.5 to 2 Hz tested. Overall, the results from this study highlighted the complex combinations of rate induced forces which contribute to the dynamic behaviour of the aircraft.

Low speed longitudinal dynamic stability analysis of a hypersonic waverider using unsteady Reynolds averaged Navier Stokes forced oscillation simulations

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. To date, low speed analyses of waverider shapes is confined to static investigations, with no studies on the dynamic behaviour ever completed. This paper presents results from unsteady Reynolds Averaged Navier Stokes simulations modelling pitching and plunging forced oscillations of the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Tests were conducted at a speed of 20 m/s, which correlates to a Reynolds number of approximately 1.5×106. Pitching and plunging oscillations were at 1 Hz with an angle of attack amplitude of 1 degree. The vehicle was analysed through an angle of attack range from -5 to 15 degrees in 5 degree increments. Results for the HEXAFLY-INT aircraft at the nominal centre of gravity location, 44.4% of the vehicle length, show that the vehicle is positively damped for all cases tested. Static derivative predictions extracted from the dynamic data showed strong agreement with existing static CFD and wind tunnel results. Further dynamic investigations conducted at a centre of gravity location of 53.1% of the vehicle length, the aft static stability limit, also showed positive damping. For these cases, the derivative magnitudes were lower, which indicates decreased damping compared to the nominal centre of gravity location. The vehicle was generally not sensitive to changes in driving frequency, with oscillation rates ranging from 0.5 to 2 Hz tested. However, during plunging tests, the pitching moment derivative was seen to change by as much as 22%. This is attributed to changes in the leading edge vortices with AoA rate. The results from this study, along with previous work looking at the static aerodynamics, stability and control authority, show the feasibility of moving to the flight test phase, but the aircraft dynamic stability in the lateral-directional planes must first be investigated.

An analytical model for airfoil aerodynamic characteristics over the entire 360° angle of attack range

The design of wind turbines requires rapid and accurate evaluation of aerodynamic loads. High-fidelity methods based on Computational Fluid Dynamics (CFD) are considered as most promising but remain expensive for predictions of aerodynamics. It is still imperative to use low or medium-fidelity methods that depend strongly on the knowledge of 360° polars. Polars can be accurately predicted by wind tunnel measurements or CFD techniques in the range of small values of AoAs up to a couple of degrees beyond the critical angle of stall; this AoA range is denoted by Dms. For higher values of AoAs, in the deep stall regime Dds, 3D effects play an important role and the determination of accurate polars is still challenging. This paper presents a semi-empirical model of force coefficients for both ranges Dms and Dds, with an appropriate transition between the two. For the range Dds, the modeling is based on assuming a nearly flat plate behavior and some symmetry properties for the force coefficients with respect to the angle of attack. The parameters of the model equations are determined from the analysis of selected experiments on airfoils associated with the characteristics of the airfoil geometry. For the range Dms, a modified formulation of the dynamic stall model of Beddoes–Leishman has been proposed. The model has been tested successfully on two airfoils, NACA 643-618 and DU97-W-300. The new approach of elaborating the polars for the whole range of AoAs provides a foundation for the application of a dynamic stall model.

An empirical model to determine lift and drag coefficients of cambered plates at moderate Reynolds numbers

This article presents the lift and drag coefficients of cambered plate blade sections of different relative camber at moderate Reynolds numbers. Relative cambers between 0% and 8% are investigated at an angle of attack range from 0° to 10°. Based on own measurements and literature data, empirical formulae are proposed for the determination of the lift and drag coefficients for Reynolds numbers within the range of 60,000 to 300,000. The formulae determine the lift and drag coefficients as a function of angle of attack, relative camber, and Reynolds number. Third-order polynomials have been proven to be suitable for the empirical formulae. The coefficients of the third-order polynomials have been determined and reported by the authors herein.

Experimental study on aerodynamic characteristics of conductors covered with crescent-shaped ice

Conductor galloping is a common disaster for the transmission lines. Among the existing analytical methods, the wind tunnel test is highlighted as the most effective approach to obtain the aerodynamic coefficients. In this paper, the aerodynamic coefficients of 12 conductor models covered with the crescent-shaped ice, which were fabricated considering the surface roughness of the iced conductor, were obtained based on the wind tunnel test. The influence of the Reynolds number and the shape parameter B, defined as the ratio of ice thickness to the diameter, were investigated. In addition, the effect of surface roughness of the iced conductor was discussed. Subsequently, unsteady areas of conductor galloping were calculated according to the Den Hartog criterion and the Nigol criterion. The results indicate that the aerodynamic coefficients of iced conductors change sharply at the attack angles of 20 and 170 with the increase of B. The surface roughness of iced conductors changed the range of attack angle, which was influenced by the increase of the Reynolds number. The experimental results can provide insights for preventing and controlling galloping.

A CFD Analysis of Wingtip Devices to Improve Lift and Drag Characteristics of Aircraft Wing

The present study investigates the use of various wingtip devices to analyse the parameters of lift and drag for an aircraft wing. The coefficients of lift and drag are investigated in this research to optimize the wing design for enhancing the aircraft performance. A reduction in the drag produced due to wingtip vortices leads to reduced fuel consumption which contributes to the reduction in fuel emissions. The two-dimensional analysis is carried out for the selection of an apposite aerofoil by comparing the lift/drag characteristics of NACA 0012, 2415 and 23015 respectively at the velocity of 79.16 m/s at the angles of attack of 0°,4°,8°,12°,16° and 20°. The aerofoil section NACA 2415 is used to design the three-dimensional aircraft wing. For the analysis of the various wing tip devices the three-dimensional wing is incorporated with the spiroid winglet, blended winglet, wingtip fence and a mini-winglet. The CFD analysis for the wing designs is carried out for the take-off and landing phases of an aircraft’s flight because the effect of vortices is the highest during these flight phases. The angles of attack range from 0° to 20°. The CFD results reveal that for the wing designs, the plain wing produced the highest drag and the blended winglet proved to be the wingtip device with the most beneficial design. The results obtained for the 30° cant angled blended winglet and 60° cant angled wingtip fence produces additional lift when compared to the results obtained for the counterpart designs. The results obtained from the analysis are in close correlation to the established use of the wingtip devices.

Flow Control over a Nonslender Delta Wing by Microsecond Dielectric Barrier Discharge Actuation

The behaviors of a pulsed microsecond dielectric barrier discharge in quiescent air are diagnosed by schlieren image and particle image velocimetry. Some localized pressure waves are induced by the discharge, propagating at a speed of about . A fairly weak vortex is also induced, with a maximum velocity of about . Wind tunnel experiments are conducted on a wing–body combination with a 47 deg swept wing. Three actuator arrangements are tested by force measurements. For the full leading-edge actuation, obvious changes of the normal forces can be achieved at high angles of attack before stall, when the actuator works at the optimum reduced frequency of . However, the stall angle is not delayed under the actuation. For front-half actuation at the leading edge, the obvious control effect is obtained at large angles of attack (22–30 deg), while for rear-half actuation, the normal force gets a relatively modest increase at a broad range of attack angles (10–34 deg). The flow pattern obtained by particle image velocimetry shows that the actuation frequency mainly determines the number of chordwise vortices coexisting along the shear layer. It is hard to engender the reattachment vortex over the wing under high-frequency actuations (such as ).

Computational hydrodynamics of a typical 3-fin surfboard setup

Surfing is becoming increasingly popular, and the economic market for surfing products is growing. The performance of the surfboards and the fins has evolved continuously through the experience and innovative spirit of surfers and shapers. However, provided performance characteristics are only subjective and of descriptive nature. Therefore, we apply and analyze objective performance indicators as (1) lift and drag coefficient for each fin and the entire configuration and (2) lift-to-drag ratio for the entire fin configuration.This numerical study investigated a commercial 3-fin configuration, mounted into a rectangular simulation region, considering the flow at several different angles of attack between 0°and 45°. RANS and URANS simulations were performed with the SST k−ω turbulence model at an inflow velocity of 5 m/s.Simulation results showed that the fins have an optimal range of attack angles where they produce the most lift. The lift forces generate a turning moment which forces the board to be turned in direction to the shore favoring the controllability and stability of the surfboard. The higher the angle of attack, the higher is the drag coefficient. Lift-to-drag ratio values showed that for speeding up small attack angles with low drag forces are preferable. Furthermore, unsteady effects as flow separation combined with vortex shedding occur at high angles of attack above 20°which can only be resolved by URANS simulations. These unsteady effects have high negative influences on stability due to high fluctuation amplitudes for lift and drag forces.In summary, this study presents, to the best of the authors’ knowledge, for the first time, steady and unsteady forces on surfboard fins and discusses their potential influences on the surfer’s controllability and stability of the surfboard during typical surfing maneuvers.