Airfoil Analysis Research Articles

Aerodynamic performance analysis of a supercritical airfoil in the helicopter main rotor

Helicopters can be considered as any-terrain vehicles, as they can take off and land at any location. The aerodynamic characteristics of helicopters are more complicated than those of fixed-wing aircraft. The rotor is the source of lift and thrust for helicopters. The complex aerodynamic characteristics of helicopters are due to their rotational frame and variations in the velocity and pressure throughout the blades. Moreover, the airfoil undergoes phase changes because half of the phase exhibits a trailing edge toward the flow. In this study, four isolated helicopter rotor blades were analyzed using ANSYS Fluent in terms of flow in a static domain under non-rotating conditions. Supercritical airfoils used in high-speed aircraft have been found to be incredibly useful in the transonic region. They increased the critical and drag divergence Mach numbers. Incorporating supercritical airfoils in helicopter rotor blades ensures suitable flow characteristics and more than 50% efficiency compared to those of the HH02 blade in a stationary frame. Analyses were conducted for HH02 and NASA SC(2)-0714 airfoils with Mach numbers of 0.3, 0.4, and 0.5 without rotation. The post-processing results prove that the NASA SC(2)-0714 airfoil rotor achieves a better aerodynamic performance than the HH02 airfoil rotor.

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.

Nonlinear aeroelastic analysis of a multi-element airfoil with free play using continuation method

In this study, the nonlinear aeroelastic response of a NACA0012 airfoil with leading-edge and trailing-edge control surfaces is studied numerically using a modified filtered impulse function method and continuation method. The source of nonlinearity comes from the free play behavior of both control surfaces which leads to the nonlinear properties of the structural stiffness matrix. The aerodynamic responses of these aeroelastic systems for varying oscillation frequencies are assumed to be linear for small deflections. These responses are developed using a reduced-order model by using the proposed modified filtered impulse function method on inviscid rotational flows computed using CFD methods for the Euler Equations. Key factors for maintaining accuracy using the proposed filtered impulse function are discussed with examples. The linearized aeroelastic equations are solved using the continuation method with the adaptive step size for three different situations that could arise in practice. The analysis process is conducted in the modes tracking and parameter variation separately. This study shows that compared to the airfoil with a single trailing-edge control surface in free play, the presence of the leading-edge flap motion could decrease the flutter speed and dominate the flutter mode in the absence of free play behavior. However, only slight differences could be observed from the limit cycle oscillations (LCO) analysis for which the structural nonlinearity is dominant owing to free play.

Aerodynamic Analysis of Membrane Wing Airfoil at Low Reynolds Numbers

Mars aircraft has been proposed as a means of extensive Mars exploration. Recent research reveals that membrane wings are effective in obtaining sufficient lift in a compact size. In this study, the aerodynamic analysis was performed by forced vibrating the wing under low Reynolds number conditions. As a result, it was found that the flows around the wing and wakes were highly affected by the geometry change.

Forward Flight Performance Analysis of Supercritical Airfoil in Helicopter Main Rotor

In this research, the aerodynamic performance and flow characteristics of NASA SC (2)-0714 airfoil and HH02 airfoil in the helicopter main rotor are evidently analyzed. The supercritical airfoil is used in the aircraft for attaining better transonic and high-speed flow characteristics. Moreover, a specialized helicopter airfoil called HH02 is used in the Apache helicopter rotor for increasing the operational speed. As most of the high-speed helicopters are using four-bladed main rotor configuration, it is analyzed with prior attention. The lift and thrust act in different directions for the forward phase of the flight whereas the lift and thrust act in the same direction for the other phases of flight, which is analyzed in this work. The computational analysis is done by using ANSYS Fluent whereas the rotational analysis is done by using the Multiple Reference Frame (MRF) method. An analysis is carried out for different RPM of 400,600 and 800 with the combination of 0.3, 0.4 and 0.5 Mach numbers with the assistance of grid independence test. The result shows that the NASA SC (2)-0714 rotor increases the thrust of the rotor around 5% to 10% under various rotor and forward speeds. Thus, the results proves that the supercritical airfoil is highly capable of producing higher thrust and good aerodynamic characteristics.

Aeroelastic Analysis of a Supercritical Airfoil with Free-Play in Transonic Flow

An investigation has been made into the nonlinear aeroelastic behavior of a supercritical airfoil (NLR 7301) considering free-play in transonic flow. Computational Fluid Dynamics (CFD) based on NavierStokes equations is implemented to calculate unsteady aerodynamic forces. A loosely coupled scheme with steady CFD and a graphic method are developed to obtain the static aeroelastic position. Frequency domain flutter solution with transonic aerodynamic influence coefficient is used to capture the linear flutter characteristic at different angle of attack (AoA). Time marching approach based on CFD is used to calculate the nonlinear aeroelastic response. The bifurcation diagram of pitching motion shows that as the airspeed increases, the limit cycle oscillation (LCO) appears then quenches, forming the first LCO branch; LCO occurs again and sustains until the divergence of the response, forming the second LCO branch. This phenomenon is essentially induced by the combined action of the static aeroelastic position caused by the camber effect of the airfoil and the S shape flutter boundary with respect to AoA.

Performance simulation of wind turbine with optimal designed trailing-edge serrations

Trailing-edge (TE) serration is a widely used instrument for noise control on wind turbine blades. Most of previous studies on TE serrations focused on noise reduction, but its aerodynamic effects on wind turbine performance have not received much attention yet. In this study, effects of serrations on the performance of a 2.3 MW wind turbine, including the power output and load characteristics, are examined using the airfoil analysis tool Rfoil and wind turbine analysis code Bladed. An optimal design method setting maximum power output as the design object is applied to determine the configurations of serrations regarding the airfoils corresponding to two sections in the last 20% span. Compared with the baseline airfoils, the serrated airfoils have higher lift-to-drag ratio at the angle of attack under the rated wind speed. For a full-scale wind turbine, the presence of serrations can slightly increase the static electrical power and the load at the blade root before the rated wind speed is achieved, and consequently increase the annual power output by less than 0.7%. However, under the turbulence wind conditions, the serrated blade has larger mean and maximum moment at the root and stronger load fluctuation, since the presence of serrations increases the angular moment of the airfoil. The analysis results suggest that using optimal designed TE serrations can achieve reduction of noise and increase of power output simultaneously, at the cost of increase of blade load.

A Coupled Inviscid–Viscous Airfoil Analysis Solver, Revisited

This paper presents a self-contained, comprehensive exposition and new elements of a classic airfoil analysis technique: an integral boundary-layer solver coupled to a vortex-panel potential-flow method. The resulting solver MFOIL, implemented in MATLAB and made freely available, builds on the XFOIL code and documentation, which serve as the inspiration, reference, and standard of comparison. Modifications made in the present implementation include an augmented-state coupled solver for more control in limiting the state update, a new stagnation-point formulation to reduce leading-edge oscillations in the boundary-layer variables, and a more robust treatment of the amplification rate near transition. Several results highlight these modifications and demonstrate capabilities of the code.

An interval quantification-based optimization approach for wind turbine airfoil under uncertainties

Wind turbine airfoil operates in the atmosphere with uncertain turbulence and relatively low Reynolds number all year round. Meanwhile, due to the complexity of blade airfoil fabrication, there are inevitable geometric deviations to the theoretical airfoil shape. These uncertainties from manufacturing and operating environment couple together and lead to performance degradation. In the traditional wind turbine airfoil design process, the uncertainties are not the design variables, objectives, and constraints are deterministic. This paper presents a novel approach for uncertain analysis and aerodynamic robustness optimization of wind turbine airfoil considering turbulence and geometric error uncertainties. An interval method coupled with the Kriging model is applied to quantify the uncertain influence, and is integrated in the optimization. The target of optimization is to find an optimal airfoil with low sensitivity to uncertainties, as well as maintaining lift to drag ratio. After optimization the min std best airfoil shows 17.96% reduction of fluctuation range and no decreased average of lift to drag ratio compared to the baseline airfoil. The optimization was validated through flow field analysis by non-deterministic CFD approach. The proposed methodology can be further applied to other engineering designs making product less sensitivity to uncertainties thus more reliable.

Comparative Aerodynamic Performance Analysis of Camber Morphing and Conventional Airfoils

This paper aims to numerically validate the aerodynamic performance and benefits of variable camber rate morphing wings, by comparing them to conventional ones with plain flaps, when deflection angles vary, assessing their D reduction or L/D improvement. Many morphing-related research works mainly focus on the design of morphing mechanisms using smart materials, and innovative mechanism designs through materials and structure advancements. However, the foundational work that establishes the motivation of morphing technology development has been overlooked in most research works. All things considered, this paper starts with the verification of the numerical model used for the aerodynamic performance analysis and then conducts the aerodynamic performance analysis of (1) variable camber rate in morphing wings and (2) variable deflection angles in conventional wings. Finally, we find matching pairs for a direct comparison to validate the effectiveness of morphing wings. As a result, we validate that variable camber morphing wings, equivalent to conventional wings with varying flap deflection angles, are improved by at least 1.7% in their L/D ratio, and up to 18.7% in their angle of attack, with α = 8° at a 3% camber morphing rate. Overall, in the entire range of α, which conceptualizes aircrafts mission planning for operation, camber morphing wings are superior in D, L/D, and their improvement rate over conventional ones. By providing the improvement rates in L/D, this paper numerically evaluates and validates the efficiency of camber morphing aircraft, the most important aspect of aircraft operation, as well as the agility and manoeuvrability, compared to conventional wing aircraft.

Airfoil Analysis and Effect of Wing Shape Optimization on Aerodynamic Parameters in a Steady Flight

The work in this paper deals with reconstructing and optimizing the wing geometry of an Unmanned Combat Aerial Vehicle for improved performance and reviewing the impact of the modification on flight parameters in a steady flight. The behavior of airfoils at planned flight conditions under I.S.A. is checked in XFLR5 software. Following up by 2-D CFD and boundary layer analysis of former and new airfoil, dimensions of the wing are re-developed, keeping the fuselage and tail structure same. The existing wing and the optimized wing design is analyzed by Vortex Lattice Method and Triangular Panel Method, with an objective to make the shape of the wing aerodynamically suitable for an increased Lift to Drag ratio and thereby minimizing drag coefficients.

The design and aerodynamic analysis of intelligent variable camber airfoils with MFC

The design and aerodynamic analysis of intelligent variable camber airfoils with MFC

Model for Enhancing Turbulent Production in Laminar Separation Bubbles

Laminar separation bubbles are one of the main critical aspects of flows at low Reynolds numbers in the range of . The flow separates in the laminar regime, the turbulence developing inside the recirculation region enhances the momentum transport, and the flow can reattach. Models based on the Reynolds-averaged Navier–Stokes equations suffer two of main issues: the determination of the transition onset and the level of the pressure recovery downstream of the reattachment of the flow. A model addressing both issues is presented in this paper. It is based on the transition model for the transition detection. The production of the turbulent kinetic energy has been properly enhanced thanks to a correlation found between the necessary boosting of and the intermittency function behavior within the bubble. The low-Mach-number and Reynolds-number flows around the Selig–Donovan 7003, Eppler 387, and NACA 0015 airfoils are analyzed. The results are compared to experimental data and large-eddy simulations available in the literature. The model can be applied to the analysis of an arbitrary airfoil without need of preliminary calculation of the transition point within the bubble.

CFD Analysis and Shape Optimization of Airfoils Using Class Shape Transformation and Genetic Algorithm—Part I

This paper presents the parameterization and optimization of two well-known airfoils. The aerodynamic shape optimization investigation includes the subsonic (NREL S-821) and transonic airfoils (RAE-2822). The class shape transformation is employed for parametrization while the genetic algorithm is used for optimization purposes. The absolute scheme of the optimization process is carried out for the minimization of the drag coefficient and maximization of lift to drag ratio. In-house MATLAB code is incorporated with a genetic algorithm to calculate the drag coefficient and lift to drag ratio of the resulting optimized airfoil. The panel method is utilized in genetic algorithm optimization code to calculate pressure distribution, lift coefficient, and lift to drag ratio for optimized airfoil shapes and validates with XFOIL and NREL experimental data. Furthermore, CFD analysis is conducted for both the original (NREL S-821) and optimized airfoil obtained. The present method shows that the optimized airfoil achieved an improvement in lift to drag ratio by 7.4% and 15.9% of S-821 and RAE-2822 airfoil, respectively, by the panel technique method and provides high design desirable stability parameters. These features significantly improve the overall aerodynamic performance of the newly optimized airfoils. Finally, the improved aerodynamics results are reported for the design of turbulence modeling and NREL phase II, Phase III, and Phase VI HAWT blades.

Analysis of various NACA airfoil and fabrication of wind tunnel to test the scaled-down model of an airfoil

Airfoil design is a major facet of aerodynamics. Various airfoils serve different flight regimes. Asymmetric aero foils can generate lift at zero angle of attack, while a symmetric aero foils exhibit no lift at the same case. The design of the Airfoil has a great influence in the lift provided to an aircraft and the thrust required to make the lift take place. The geometry design of the airfoil is carried through Design Modeler. The analysis work of the airfoil is carried using Ansys Fluent. The coefficient of lift and drag are calculated through constant density throughout the section.

Aerodynamics Analysis of a Slotted A4412 Wind Turbine Airfoil Using CFD / Case Two

The static pressure, dynamic pressure and velocity magnitude are important parameters and have a strong influence on airfoil lift force. In this paper a slotted NACA4412 airfoil profile is considered for analysis by using the commercial code ANSYS-FLUENT 14.5® at an inlet boundary condition of different approaching wind velocities for various airfoil angles of attack in the range 0?to 24?. Renormalized group (RNG) k-? turbulence model with enhanced wall function is used for the analysis due its’ wide usage in the aerodynamic industry. Variations of the physical properties like static pressure, dynamic pressure and velocity magnitude are plotted in form of contours and/or vectors. The main aim of the research is to find out a method to enhance the efficiency of the selected airfoil and its’ workability in a wide range of low and high wind speeds which might make it suitable for installation and operation in different climates.This feasibility of enhancing the lift is and/or minimizing the drag is done by CFD on a series of independently modified NACA4412 airfoils. The current one is called Case 2. The analysis output of Case 2 is not encouraging. It does not show any improvement in NACA4412 airfoil efficiency and therefore it is classified as (obsolete).

A pathway towards sustainable development of small capacity horizontal axis wind turbines – Identification of influencing design parameters & their role on performance analysis

Presently small wind turbines are receiving greater attention, due to the extensive promotion of decentralized power generation in a sustainable way by national and international organizations. However, there are many obstacles in commercializing these turbines on a large scale due to lower efficiencies of turbines associated with high vibrational losses, lack of technical knowledge with the manufacturers, cost criteria and lack of awareness among the end-users. This paper reviews the research works done in the design and development of small wind turbine blades, including diffusers and winglets addition. Performance & parametric analysis of airfoils, blades & wind turbines are presented comprehensively. Impact of maximum power point technique, effects of ambiance on the turbine performance, environmental impacts of small wind turbines and some novel concepts are presented in this review. Future research works to enhance the efficiency of small wind turbines using materials with high strength to weight ratio would pave the way for efficient utilization of available wind energy in the earth’s crust.

Numerical Analysis of Circular Arc Airfoil at Low Reynolds Numbers

Numerical Analysis of Circular Arc Airfoil at Low Reynolds Numbers

Boundary Layer Transition Measured by DIT on the PSP Rotor in Forward Flight

A well-defined reference set of data for computational fluid dynamics and comprehensive code validation for a scaled helicopter main rotor with boundary layer transition in forward flight is presented. The boundary layer transition was measured using differential infrared thermography (DIT) on the top (suction) side of the NASA/Army “PSP rotor” in the NASA Langley 14-by-22-Foot Subsonic Tunnel. The tests used a FLIR X8500 SLS long-wave infrared camera to observe the three-bladed rotor. The boundary layer transition was detected for forward flight at an advance ratio of 0.3 (115 kt). The measured boundary layer transition positions are consistent with previous measurements and predicted boundary layer transition locations. A method for the analysis of DIT images for a rotor in forward flight is shown and validated based on computational analysis of a pitching airfoil with varying inflow, showing both qualitative and quantitative similarity to experimental data.

Aerodynamic Analysis and Optimization of Airfoils Using Vortex Lattice Method

Air transport is one of the fastest means of transport in the modern world. Aircraft’s efficiency depends on the efficiency of its subparts and its subsystems individually. For example, the gas turbine used as main source of thrust in aircrafts has to be largely efficient, which adds to the overall efficiency of the aircraft. The same way, another important part of the aircraft is the wing. Wings are the main reason for an air vehicle to fly. Aerodynamic parameters like lift, drag and the ratio of co-efficient of lift to drag which is CL/CD ratio determines the efficiency of the aircraft wing. This CL/CD ratio depends on the cross section of the wing, i.e. the airfoil. This paper emphasizes aerodynamic analysis on airfoils NACA 0018, NACA 2412, NACA 4412, USA 45, TSAGI-S12 and B737A used on different planforms of an aircraft wing like Rectangular, Elliptical, Delta and Swept back wing. The results are analyzed and the best airfoil corresponding wing shape is reported. This best airfoil is further refined effectively to get high CL/CD ratio. The complete analysis and airfoil optimization were carried on XFLR5 software which is governed by Naiver-Stokes equations. The airfoils were analyzed for a velocity of 50 m/s, at an angle of attack of 7°, up to a maximum Re (Reynolds Number) of 3e+06, the wing chord length at root, CR=1m and total wing span, L=10m was kept constant throughout the analysis for uniformity. Post analysis, the best three airfoils were further interpolated and refined to obtain higher CL/CD ratio.