Various Angles Of Attack Research Articles

Effect of the Blade Pitch on the Performance of Small Wind Turbine Exposed to Wind Stream of Various Angles of Attack

In wind turbines, several parameters can affect the productivity of the turbine, such as wind velocity, rotor area, blade aerodynamic design, and blade pitch. In this paper, the effect of various pitch angles for a small wind turbine was investigated. A system of two metal stands with same height is installed (i.e. on the same axis of streaming), the first stand holds an air blower which imitates the wind with constant air blowing. The other, holds a small wind turbine consists of a DC motor and metal hub (steel bush) with 3-blades with equal radial distance (120°). The pitch angle was adjusted at a certain degree of inclination (10°) in which the turbine stars to rotate, then readings of power and rotational speed were collected. The process then repeated with another 3 different angles (15°, 20°, and 25°). At the end, a fixed pitch angle degree was adjusted, and then the lowest and highest air velocity that affecting the blades rotation were measured.

On the aerodynamic loads and flow statistics of airfoil with deformable vortex generators

The aerodynamic performances and flow statistics for a Delft University-91-W2-250 airfoil with deformable vortex generators (DVG) were experimentally studied in a wind tunnel across various angle of attacks and wind speeds. A high-resolution force sensor was used to measure the time-averaged lift force, while a planar particle image velocimetry system was applied to characterize the mean velocity and vortex shedding over airfoil surface. The results highlighted that, similar to conventional rigid vortex generators (RVG), DVG can effectively enhance lift coefficient after the stall angle of airfoil with clean surface under low incoming winds. However, the deformation of DVGs increased with the growth of wind speed; this suppressed the effectiveness of wake mixing where the aerodynamic performance of DVGs gradually converged to clean surface configurations. The flow measurements demonstrated that the deformation of DVG can lead to significant decrease in near-wall flow velocities close to the airfoil trailing edge and generate more dispersed vorticity distributions. To further investigate the linkage between DVG deformation and its wake mixing effectiveness, complementary tomographic particle image velocimetry measurements were conducted. The results indicated that the vorticity strength presented monotonic decay with the bending angle of DVG within both near and intermediate wake regions. The capability of DVGs passively adjusts their bending angle, and therefore, the airfoil lift coefficients provide a novel approach to reduce aerodynamic load fluctuations for aircraft within unsteady flows.

Blockage effect of a wall on the hydrodynamic characteristics of a supercavitating vehicle's aft body

When the hydrodynamic characteristics of a supercavitating vehicle are tested in a water tunnel, the blockage effect of the wall compresses the diameter of the supercavity, distorting the hydrodynamic force curves. In this paper, computational fluid dynamics (CFD) simulations are used to investigate the hydrodynamic characteristics of a supercavitating vehicle model for various angles of attack, and the simulation results are validated experimentally. When the blockage ratio is less than 0.002295, the blockage effect on the cavity can be neglected. However, for available water tunnels and model sizes, the blockage effect is unavoidable, changing the free and critical angles of attack in the hydrodynamic force curves. The simulation results and conclusions are useful for correcting the results of water tunnel test results influenced by the blockage effect.

Assessments of surface heat flux from rapid temperature sensors at various angles of attack over a plate

Assessments of surface heat flux from rapid temperature sensors at various angles of attack over a plate

Aerodynamic Performance of a Dragonfly-Inspired Tandem Wing System for a Biomimetic Micro Air Vehicle.

The flying agility demonstrated by dragonflies is accomplished by means of complex aerodynamic forces produced by flapping their four wings arranged in a tandem configuration. The current study presents a novel tandem flapping wing mechanism for a biomimetic air vehicle that was designed and manufactured to experimentally investigate the aerodynamic forces. By optimizing the configuration and using spatial network analysis, it is shown that the designed structure can flap the wings in a linear up–down stroke motion and is capable of maintaining good consistency and aerodynamic performance. Such a mechanism could be used in a future biomimetic micro air vehicle (BMAV) design. The mechanism uses an electromagnetic actuator to flap the wings with a variable beat frequency (30–210 Hz) at various angles of attack (−10°–20°). The results show that the tandem wings generate approximately 50% higher lift than the forewing or hindwing pairs acting alone. Tandem wings also improve stability, which could potentially allow hovering.

Computational Investigation into Prediction of Lift Force and Resistance of a Hydrofoil Ship

The characteristics of the fore and aft foils at the various angles of attack incorporated with forward velocities have been vulnerable to induce strong nonlinearities to dynamic lift force and ship resistance. Then, a computational simulation is necessarily required to predict their performances in the calm water condition. This paper presents a computational investigation of the hydrofoil ship on predicting lift and ship’s resistance using fluid dynamic (CFD) simulation approach. Several parameters such as Froude numbers and the angle of attacks both of fore and aft foils have been accordingly taken into account. The results revealed that the subsequent increase on angle of attack of fore and aft foils was directly proportional to the lift force and the ship’s resistance. In addition, the lift force of the aft and fore foils with the angle of attacks of 10 degrees and 5 degrees, respectively, resulted in the significant increase of the lift force and the ship’s resistance. However, the subsequent increase of Froude number from 1.382 up to 1.626 has insignificant effect to the lift and the ship’s resistance of the hydrofoil. It can be concluded that CFD simulation is very beneficial to ensure an operational effectiveness of hydrofoil design towards prediction on the lift force and the hydrofoil’s resistance at the preliminary design stage.

Numerical Investigation on the Effect of Leading-Edge Tubercles on the Laminar Separation Bubble

The effect of leading-edge tubercles on the aerodynamic performance of E216 airfoil is studied by steady 3D numerical simulations using Transition γ−Reθ turbulance model. The investigation is carried out for the various angles of attack in the pre-stall region at Reynolds number of 100,000. Various tubercle configurations with different combinations of amplitude ranging from 2 mm to 8 mm and wavelength varying from 15.5mm to 62 mm are studied. The effect of tubercle parameters on the laminar separation bubble (LSB) is extensively studied. Improvement in the coefficient of lift (Cl) is observed for most of the tubercled models and is significant at high angles of attack. But the simultaneous increase in the drag coefficient resulted in a marginal improvement in the coefficient of lift to drag ratio (Cl/Cd) for most of the cases except for A2W62, which produced a peak value of 46.91 at AOA 6◦ which is higher than that for the baseline by 7.37%. Compared to the baseline, the magnitude of suction peak is higher along the trough and lower along the peak. The low amplitude and low wavelength tubercle model exhibited smooth surface pressure coefficient (Cp) distribution without any sign of strong LSB formation. The LSB moves upstream with the increase in amplitude and wavelength. The LSB along the trough is formed ahead of that at peak inducing three-dimensional wavy shaped LSB unlike the straight LSB as in baseline. Two pairs of counter rotating vortices are formed on the airfoil surface between the adjacent peaks at two different chord-wise locations which strongly alter the flow pattern over it.

Flow Separation Control on NACA0015 Airfoil Using Synchronized Jet Actuator

In this study, a novel fluidic jet actuator is designed to control flow separation on a NACA0015 airfoil at various angles of attack. The U-shaped jet actuator has two rectangular slots implemented near the leading edge of the airfoil. It is driven by a piston mechanism and operates at three excitation frequencies. Depending on the motion of the mechanism, a synchronized jet flow is generated by blowing and suction at the dual exits of the actuator slots. The experimental studies are carried out in a subsonic wind tunnel. The unsteady 2D Computational Fluid Dynamics simulations are performed by Detached Eddy Simulation with the SST k-ω turbulence model where measured jet velocities at the exits of the actuator slots are imposed as boundary conditions to mimic motion of the piston. The results at the on-mode and off-mode of the actuator are evaluated in terms of surface pressure coefficient distributions on the airfoil and averaged aerodynamic force coefficients. At low angles of attack, there is an adequate match between numerical and experimental results for the base flow without any control. At higher angles of attack, flow separation becomes considerably dominant and stall prevention by active flow control is detected especially at high excitation frequencies‎.

Load estimation in unsteady flows from sparse pressure measurements: Application of transition networks to experimental data

Inspired by biological swimming and flying with distributed sensing, we propose a data-driven approach for load estimation that relies on complex networks. We exploit sparse, real-time pressure inputs, combined with pre-trained transition networks, to estimate aerodynamic loads in unsteady and highly separated flows. The transition networks contain the aerodynamic states of the system as nodes along with the underlying dynamics as links. A weighted average-based (WAB) strategy is proposed and tested on realistic experimental data on the flow around an accelerating elliptical plate at various angles of attack. Aerodynamic loads are then estimated for angles-of-attack cases not included in the training dataset so as to simulate the estimation process. An optimization process is also included to account for the system's temporal dynamics. Performance and limitations of the WAB approach are discussed, showing that transition networks can represent a versatile and effective data-driven tool for real-time signal estimation using sparse and noisy signals (such as surface pressure) in realistic flows.

Manufacturing, Assembly and Integration of a Large Scale Composite Wing Wind Tunnel Model and the Design and Implementation of an associated Measurement System

Building a wind tunnel model with an innovative aerodynamic design including a laminar airfoil concept and morphing parts requires a suitable manufacturing and assembly plan to transfer the virtual model to concrete reality.The contribution of the INVENT GmbH within the GRETEL consortium is the manufacturing of the main structural components of the Wing and the integration of the Wind Tunnel Model. To realize such a precise projection, the main approach is to implement a high overall accuracy of the later model by realizing a low percentage of geometry deviation already on piece part level. Beginning with a material dedicated tool design concerning cure cycle parameters and induced strain effects, for aspects of geometrical manufacturing accuracy, also suitable inspection techniques, regarding the verification of structural requirements and material conditions are implemented in the integration process at specified steps.A further part of the integration process of the GRETEL Wind Tunnel Model is the installation of application-related measurement equipment. The Institute of Composite Structures and Adaptive Systems of the German Aerospace Center (DLR) is responsible for the design and realization of such a project customized measurement concept. For the measurement of the pressure distribution along the profile contour with various angles of attack and wing configurations during the testing, the wing is equipped with several pressure taps. Further, the measurement equipment spectrum covers also the registration of acceleration forces and mechanical loads of the inner wing structure components. This concept creates a holistic picture of the coherences between aerodynamical and mechanical dimensions for each tested configuration.The implementation of all aforementioned aspects into the large-scale model is elucidated and discussed in the light of morphing parts of the model being delivered by another project. The integrated equipment is described and the impact of the integration into the design and assembly of the overall model is illustrated.

Effect of Angle of Attack on Pressure Distribution of NACA5520 Airfoil Blade

In this project work, experiments are carried out in low-speed subsonic wind tunnel and 30-port multitube manometer used to study the aerodynamics characteristic of cambered airfoil model NACA5520 with different velocity range and various angle of attack. Experiments were made to investigate the pressure distribution over the airfoil under velocity range from 5m/s, 10m/s, 15 m/s, and 20 m/s and various x/s locations as 0.25, 0.5, and 0.75. The pressure measurements were taken using a multi-tube manometer and pitot-static tube over the cambered airfoil at different angles of attack. Hence, the distribution of the pressure coefficient (Cp) is calculated for the different operating conditions on the tapered blade. Also, the effect of pressure distribution over the tapered blade at different velocities and AOA is studied in spanwise location of the blade.

A deep learning approach for the transonic flow field predictions around airfoils

Learning from data offers new opportunities for developing computational methods in research fields, such as fluid dynamics, which constantly accumulate a large amount of data. This study presents a deep learning approach for the transonic flow field predictions around airfoils. The physics of transonic flow is integrated into the neural network model by utilizing Reynolds-averaged Navier–Stokes (RANS) simulations. A detailed investigation on the performance of the model is made both qualitatively and quantitatively. The flow features associated with the transonic effects and the angle of attack variation, such as the shock waves and the flow separation, are well predicted. Furthermore, predicted flowfield data are used to compute the aerodynamic coefficients. The findings indicate that the presented model may allow avoiding time-consuming computational fluid dynamics (CFD) simulations, especially in the design optimization studies with a slight loss of accuracy.

Comparative Numerical Aerodynamics Performance Analysis of NACA0015 and NACA4415 Airfoils

The climate crisis caused by global greenhouse gas emissions has led to many disasters around the world in recent years. Some of these disasters are floods in various parts of Europe, melting of Arctic glaciers, and rising water levels in the oceans. People living on islands in Southeast Asian countries are forced to migrate due to rising water levels. With the increase in the frequency of such situations, life on earth is at risk. Greenhouse gas emissions harm not only humans but also animals and plants. The most effective measure that can be taken against this is to stay away from fossil fuels. With the use of fossil fuels, the carbon ratio in the atmosphere increases, and climatic imbalances occur. For this reason, the interest in alternative energy sources is increasing. Wind energy is one of the most widely used renewable energy sources. This is due to the low cost of installation and ease of use. The most important factor affecting the aerodynamic efficiency of wind turbines is the blade profiles. Numerous types of wing profiles have been designed and put into use. In this study, numerical analyzes of NACA 0015 and NACA 4415 airfoils at various angles of attack were performed by determining forces every five degrees between 0 and 20 degrees using ANSYS Fluent commercial software. Lift coefficients and drag coefficients were also calculated for the angles of attack used. According to the analysis results obtained, optimum attack angles were found for each airfoil. As a result, NACA0015 and NACA4415 airfoils were compared in terms of their performance.

The Numerical Investigation of Combustion Performance of Scramjet Combustor with Variation in Angle of Attack

The Numerical Investigation of Combustion Performance of Scramjet Combustor with Variation in Angle of Attack

Performance analysis of aircraft composite winglet

In this work, the aerodynamic and structural investigation of the winglet is done experimentally. The lift force and the drag force are acted on the winglet. The modification is done in the winglet to improve the lift force capacity and minimize the drag effect. Several angles of attack such as 450, 550, 650& clean wing is investigated in this work. The experimentation is done in the wind tunnel for several angles of attack on the winglet. Further, the experimentation value is compared with the theoretical value. The drag coefficient, maximum CI and minimum CD at various angle of attack is obtained from the experimentation. The prototype model is designed in CATIA V5 software. The ANSYS software is used for numerical analysis. From the numerical and experimental results, the effective winglet model is obtained.

Numerical analysis of vertical axis wind turbine blades in ANSYS Fluent

The limitation of the source and storage of fossil fuel and the rapid mitigation due to the rise of population, the renewable energy is the only key for the problem. Among the renewable energies, wind energy becomes the most promising potential as it is a green energy, and this research is focused on the same. The present study investigates the wind turbine blade simulation analysis for a vertical axis wind turbine blade based on the design parameters of NACA0018 airfoil. In this investigation, computational fluid dynamics analysis of vertical axis wind turbine blade is simulated by varying the angle of attack ranging from 12° to 15° while maintaining an incoming wind velocity of 8 m/s. Finite difference-based software “ANSYS FLUENT” is utilized for the simulation of this angle of attack analysis on vertical axis wind turbine considering the turbulence to be SST k-∊ model. Vertical axis wind turbine’s efficiency surely depends upon the blade profile and its orientation. Throughout the blades, velocity and pressure distribution is analyzed at different tip speed ratio with constant inlet velocity. The parameters like tip speed ratio, lift coefficient and power coefficient are reported in this study. In this study, at various angle of attack, simulation shows the uniform velocity distribution at optimum angle of attack of 15° and validation is done by drafting a graph between power coefficient and tip speed ratio, and for given angle of attack, lift coefficient is also validated via graph and feasible value of 1.689 is obtained from the simulation at angle of attack of 15° and comparison is also done by using velocity and pressure contours of blades at different angle of attack.

Numerical investigation of flow over a hemispherical missile nose cone configuration in subsonic speed

Numerical investigation of flow around an hemispherical nose cone missile was simulated for very low speed flow conditions. The geometry creation, meshing of geometry, solving and post processing was done in ANSYS - Fluent. This research uses CFD at the subsonic range to analyze missiles with hemispherical nose cones at various angles of attacks from 0° to 16° with step of 4° deg and different velocity ranging from 5 m/s to 20 m/s. This study estimates the aerodynamics characteristics such as the coefficient of drag and lift. Besides, distribution of the coefficient of pressure over the surface of the hemispherical missile nose cones and their graphical result are ploted and presented.

On the stall flutter occurrence in a blade cascade set to turbine and compressor geometry

A blade cascade allowing free pitch movement of five blades was developed in Institute of Thermomechanics. This model is introduced to study the phenomenon of stall flutter existing in rotary bladed wheels of steam turbines and other devices. This article describes how to induce the stall flutter for prescribed boundary conditions (as inlet velocity, various angles of attack, etc.) and gives survey about flow field differences around the cascade set to both the turbine and the compressor geometry. This experimental research utilized time-resolved Particle Image Velocimetry (PIV) to measure and to evaluate statistical quantities of the wake behind the NACA0010 profiles of the cascade. Also dynamical analysis was performed in the form of Fast-Fourier transform and also phase-locked measurement was applied. Gained knowledge will be utilized to design advanced model of the cascade allowing stall flutter examination without the use of ball bearings.

DETERMINATION OF DRAG AND LIFT RELATED COEFFICIENTS OF AN AUV USING COMPUTATIONAL AND EXPERIMENTAL FLUID DYNAMICS METHODS

Determination of hydrodynamic coefficients is a vital part of predicting the dynamic behavior of an Autonomous Underwater Vehicle (AUV). The aim of the present study was to determine the drag and lift related hydrodynamic coefficients of a research AUV, using Computational and Experimental Fluid Dynamics methods. Experimental tests were carried out at AUV speed of 1.5 m s-1 for two general cases: I. AUV without control surfaces (Hull) at various angles of attack in order to calculate Hull related hydrodynamic coefficients and II. AUV with control surfaces at zero angle of attack but in different stern angles to calculate hydrodynamic coefficients related to control surfaces. All the experiments carried out in a towing tank were also simulated by a commercial computational fluid dynamics (CFD) code. The hydrodynamic coefficients obtained from the numerical simulations were in close agreement with those obtained from the experiments.

Experimental investigation of NACA-0012 airfoil instability noise with sawtooth trailing edges

This study presents an experimental study of the effect of sawtooth trailing-edge serrations on airfoil instability noise. The far-field noise measurements are obtained to investigate the noise radiation characteristics of a NACA-0012 airfoil operated at various angles of attack: 0°, 5°, and 10°, and covered Reynolds numbers of 2.87 × 105, 3.71 × 105, and 5 × 105. It is found that as the Reynolds number increases, the instability noise shifts from tonal to broadband, whereas as the angle of attack increases, it shifts from broadband to tonal. Furthermore, sawtooth trailing-edges are used to minimize instability tonal noise, leading to considerable self-noise reduction. Parametric studies of the serration amplitude 2 h and streamwise wavelength λ are performed to understand the effect of sawtooth trailing-edges on noise reduction. It is observed that the sound pressure reduction level is sensitive to both the amplitude and streamwise wavelength. Overall, the sawtooth trailing-edge with larger amplitude and smaller wavelength produce the greatest amount of noise reduction.