Airfoil Model Research Articles

Convolutional neural network for determining the flow field around an airfoil and blunt-based models

The convolutional neural network is widely applied in the classification of images and medicine. Some current networks are used in aerospace engineering and show a high potential in determining aerodynamic forces and flow fields. This article constructs a convolutional neural network for predicting pressure and velocity fields around a two-dimensional aircraft wing model (airfoil model). Training data is computed using the Reynolds-averaged method, and then extracted, focusing on the flow around the wing. Input data includes geometric parameters, and airfoil inlet velocity, and output data includes pressure field and flow velocity around the airfoil. The convolutional neural network is based on improving the U-Net network model, commonly used in medical applications. The results show that the convolutional neural network accurately predicts flow around the airfoil, with an average error below 3%. Therefore, this network can be used and further developed to predict flow around the wing. The network is then applied to predict the pressure and pressure fields around a blunt-based model with different aspect ratios. The main feature of the flow can be extracted from the network. Results related to pressure distribution, velocity, and method error are presented and discussed in the study. This study also suggests improving the network and applying it to pressure and velocity fields in aerospace engineering

An experimental and numerical investigation on aerodynamic characteristics for different airfoil sections for external flow

This research presents the development of a subsonic wind tunnel designed for streamlined airflow, featuring a squared cross-sectional area along its length. The primary focus is on measuring drag and lift on external flow across two different airfoil models. Utilizing a variable-speed centrifugal blower motor in the absence of converging and diverging sections ensures streamlined airflow in the test section. Two airfoil models, NACA-0012 and NACA-2414, fabricated from galvanized iron thin gauge sheet metal, undergo analysis through wind tunnel experiments and numerical simulation. Within the wind tunnel, strain gauge load cells are incorporated to accurately measure drag and lift across the airfoils. Comparative assessments of drag and lift coefficients are conducted at four varying angles of attack (-6.3 degrees to 12.6 degrees) for each airfoil. Results from both wind tunnel experiments and numerical simulations demonstrate precision, closely aligning with literature.

Smoke Line Geometry Impact on Airfoil Model Flow Visualization

This study discusses the analysis of airflow visualization on a NACA 4412 airfoil model using a fluid mixture technique with variations in smoke line geometry. The main objectives of this study are to understand the behavior of airflow around the airfoil surface under different test conditions and methodology used involves flow simulation and experimental tests with fluid mixtures that produce flow visualization through various smoke line geometries, such as straight lines, zigzags, and curves. The test results show that variations in the shape of the smoke line produce different flow at the boundaries of the airfoil surface, which significantly affect the pressure distribution and lift coefficient. These findings provide important insights for the development of more efficient airfoil designs and the application of flow visualization techniques in aerodynamic testing.

DESIGN OF TAPERED WIND TURBINE USING VARIOUS NACA 24112 AIRFOILS IN SEMAYAN VILLAGE CENTRAL LOMBOK REGENCY

This research focuses on designing and optimizing a tapered wind turbine employing NACA 24112 airfoils, specifically tailored for Semayan Village in Central Lombok West Nusa Tenggara province. Given the escalating global energy demand and the depletion of fossil fuels, the study aims to explore alternative energy solutions. The chosen horizontal axis turbine, equipped with an increased number of blades, seeks to maximize the power coefficient and overall efficiency. The NACA airfoil model, coupled with Q-Blade v0.963 software, was employed for simulations after conducting wind speed measurements in Semayan Village. The collected data indicated moderate wind speeds, aligning with the selection of the Taper blade design. The blade design process involved comprehensive system efficiency calculations and twist angle optimizations to enhance overall turbine performance and extend its lifespan. Rotor simulations revealed a noteworthy peak in the power coefficient (Cp), reaching 45% at Tip Speed Ratio (TSR) 7, indicating an optimal point for power generation. However, the study emphasizes the importance of selecting an appropriate TSR, as efficiency diminishes at higher TSR values. This research highlights the potential of wind energy as a viable and sustainable solution, particularly for regions with limited access to electricity. It advocates for the broader adoption of renewable energy sources to address the evolving energy landscape.

INVESTIGATION OF AERODYNAMIC PERFORMANCE OF A NACA 0021 AIRFOIL MODIFIED WITH CAVITY

In this paper, an experimental investigation was conducted to investigate the effect of cavity on the NACA 0021 airfoil at low Reynolds number. The force measurement and smoke-wire flow visualization experiments were conducted in a low-speed open suction wind tunnel with a test section of 57cm×57cm×100 cm at a Reynolds number of 5.0×104 and 1.0×105. Two different airfoil models produced for the experiments such as base and cavity models. The diameter and location of the cavity was chosen as 0.08C and 80% x/C, respectively. The maximum lift coefficient of the cavity modified airfoil was increased about 6% for both positive and negative angles of attack compared to base airfoil at Reynolds number of 1.0×105. The cavity modified airfoil showed higher lift coefficient values at negative attack angles when compared to base airfoil at Reynolds number of 5.0×104.

Enhancing output characteristics of semi-active flapping airfoil energy capture device via flexible deformation strategy

ABSTRACT A concentrated-torsion flexible airfoil model is established to enhance the output characteristics of the flapping airfoil energy capture device in this work. The effect of the damping ratio C 2*, spring ratio K 2* of the torsion spring, and mass ratio M A * of the tail airfoil on the dynamic characteristics is investigated systematically. The numerical simulation results show that compared with the rigid airfoil, the time-averaged power coefficient and output efficiency of the optimized flexible airfoil (C 2* = 4, K 2* = 0.5, and M A * = 0.7) are increased by 91.85% and 63.45%, respectively. Remarkably, the output efficiency of the optimized flexible airfoil is 32.15%. The reason for the enhanced performance is that the passive deformation can ensure the airfoil generates a stronger vortex and delays the shedding of the vortex. In addition, the experimental test results (with a 36.29% performance enhancement) further demonstrate the effectiveness of using the concentrated-torsional flexible deformation strategy in enhancing the energy output characteristics of the flapping airfoil.

Data-driven flutter suppression of noised airfoil models: model identification and robust sliding mode control designed with multi-level control surfaces

Data-driven flutter suppression of noised airfoil models: model identification and robust sliding mode control designed with multi-level control surfaces

Improvement of the airfoil lift and drag characteristics using plasma-efficient flow control

Flow control is studied to improve the aerodynamic performance of an aerofoil. A strategy for maintaining the near-wall flow structure with a given spatial scale, developed within the framework of interdisciplinary research, is used. The proposed active flow control method is based on the application of spanwise arrays of mechanical, thermal, or plasma vortex generators. The latter are found most versatile and efficient for the formulated goal. Aerodynamic coefficients measured in the specified wind tunnel are discussed for the 12.5% supercritical airfoil model. The model is controlled by the spanwise array of pulsating high-voltage plasma discharges. This multi-actuator system provides a sufficient number of control parameters such as pulse duration and repetition rate, the distance between the neighboring actuators (space scale of generated disturbances), and the plasma array location along the airfoil chord. Measurements in a range of Reynolds numbers of Rec=(3-7)x105 showed growth of a maximal lift coefficient CLmax up to 10% and the stall angle by 1.5°-3.5° accompanied by drag reduction up to 7%.

Noise reduction of an airfoil model covered by bio-inspired herringbone riblets

It is curious that whether the typical herringbone pattern of bird flight feathers plays a role in attenuating aeroacoustic noise. Being motivated by this, experiments are conducted to investigate noise reduction of the NACA0012 (National Advisory Committee for Aeronautics) airfoil-based model with one side surface covered by bio-inspired herringbone patterns of riblets. The herringbone-ribbed surface is defined by the divergent angle β (= 60°) of the riblets pattern, the spanwise wavelength λ (= 0.2c and 0.4c) of the pattern, and the riblet height h (= 0.6%c and 1.2%c), where c is the chord length of the airfoil. While far-field sound pressure fluctuations are measured via microphones in an anechoic wind tunnel, flow fields around the model are captured using particle image velocimetry (PIV) in a water tunnel. The effective angle of attack of the test models ranges from αeff = −11.1° to 11.1° and Reynolds number considered is from Re = 2.3 × 105 to 7.8 × 105. Compared with the baseline smooth models, the models with the riblet pattern on the pressure side are able to substantially suppress the tonal noise, associated with considerable reduction in the overall noise. The reduction in the overall sound pressure levels of the tonal noise and the overall noise are up to 21.3 dB and 20.5 dB, respectively, at αeff = −2.2° and Re = 3.6 × 105. The noise reduction is attributed to the transition of laminar to turbulent boundary layers over the herringbone-ribbed surface, particularly in the saddle location where the spanwise-repeated herringbone pattern converges. Behavior of shear layers separating from the trailing edge of the model is examined, corroborating the proposition that the acoustic feedback loop is impaired by the herringbone-ribbed surface.

Research of Aerodynamic Airfoil with Vortex Ceerators in Wind Tunnel

This article deals with researching the aerodynamic airfoil model in the wind tunnel using volume vortex generators. The volumetric vortex generators of three types for the definite blowing model are described including their geometrical characteristics. The features of volume vortex generators mounting on the surface of the aerodynamic airfoil model are represented. Features of the experiment in the wind tunnel are described. Comparative changes in aerodynamic characteristics of the aerodynamic airfoil model with and without volume vortex generators in the form of graphical dependencies have been shown. The comparison has been made for different values of Re numbers. The analysis of the obtained dependencies has carried out. The visualization of airflow in an experimental way is illustrated. The results are directed at improving the aerodynamic characteristics of unmanned aerial vehicles. The main significance of the research lies in improving the behavior of unmanned aerial vehicles in the area of critical angles of attack. The obtained results can also be useful for aircraft of the wide class.

Separation and reattachment fixed Reynolds-stress model for iced airfoil and wing simulations

Differential Reynolds-stress models (RSMs) are the higher level of Reynolds-averaged Navier-Stokes (RANS) modeling and generally considered to have more potential than eddy viscosity models (EVMs) when applied to separated flows. Nevertheless, some peculiarities have been observed in simulating flows over iced wings. The first is the numerical stability problem caused by non-streamlined wall surfaces. To weaken this, a wall-boundary-natural scale λ=ω−1/8 is introduced into SSG/LRR RSM in this paper. The second is to remedy the problem of the unsatisfactory non-equilibrium characteristic in separating shear layer (SSL), a correction determined by anisotropy of Reynolds normal stresses is developed. The last focuses on the unphysical backbending of the streamlines near stagnation/reattachment (SR) points. Since the SSL correction will worsen this defect, a SR correction is carried out to blended with it. Four two-dimensional iced airfoils and a three-dimensional iced wing are simulated and then the above measures are confirmed to be the positive.

تعزيز الخصائص الديناميكية الهوائية عن طريق تعديالت سطح الجنيح

The enhancement of the aerodynamic characteristics of the NACA0012 airfoil is studied numerically. ANSYS Fluent is used to simulate the airfoil's performance by applying certain surface modifications in the form of dimples and protrusions. Different shapes were used, namely, semicircular, v-shaped and square. Analysis has been done on an airfoil of 1m chord length with these modifications, which were implemented on the upper surface of a twodimensional airfoil model and placed at 75% of chord length. A comparative study of surfacemodified airfoil models was done to investigate lift and drag for a constant at Re = 3.0E6 at various angles of attack and compare them with smooth airfoils. The results reveal that the aerodynamic characteristics were improved by applying surface modifications, and the flow separation on the airfoil can be delayed by using dimples and protrusions on the upper surface. It was found that the semicircular dimples and v-shaped bumps have the best aerodynamic enhancement, where the lift coefficient was improved by 11% and 9% compared to smooth airfoils, respectively, while the drag coefficients were reduced by 3% for both shapes. Also, based on these surface-modified airfoil analyses, the stall angle was increased by two degrees. In comparison, the semicircular dimples are more suitable for enhancing the performance characteristics of airfoils.

Unsteady nonlinear lifting line model for active gust load alleviation of airplanes

Active gust load alleviation is an important technology for designing future passenger airplanes to be lighter and thus more environmentally friendly. Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations are typically used to accurately calculate gust loads, but because of their high computational cost, they can only be performed at a few selected operating points. In simpler potential theory models, stall is neglected, resulting in loss of accuracy. In this paper, a low-order unsteady aerodynamics wing model is presented, which is able to represent well compressible flow with stall. Furthermore, the model offers the possibility to modularly incorporate actuators, which allows the design and evaluation of active load alleviation systems. The model is based on a conventional unsteady 2D airfoil model including a dynamic stall model. The dynamic stall model requires viscous steady coefficients, e.g. from 2D steady RANS computations. This 2D airfoil model is coupled with a 3D steady-state lifting line model. The model is applied to the LEISA research airplane and extensively validated with URANS results. It performs well in calculating gust loads with and without simultaneous flap deflections, and provides significantly more accurate results in the case of stall than when stall is neglected.

Overall aerodynamic performance of the airfoils with different amplitudes via a fuzzy decision making based Taguchi methodology

In this study, the overall aerodynamic performance of the airfoils with variable amplitude geometric structure for lift-type vertical axis wind turbine has been analyzed and optimized using Fuzzy Analytic Hierarchy Process (AHP)-Fuzzy COmbinative Distance-based Assessment (CODAS) based on Taguchi Method. In the design of the experiment, leading edge (LE) tubercle airfoil models, Reynolds number, and angle of attack are utilized as the control factors. Drag, lift, and lift to drag ratio performances by comparing the airfoils according to the baseline model are calculated and the combination of these performances is considered as the overall aerodynamic performance response. The experiments are carried out according to the orthogonal matrix L18. Since the importance of each response is different on lift-type vertical axis wind turbines, the importance weights of these responses were obtained by Fuzzy AHP according to the evaluation of the decision maker. Multiple responses are converted into a single response (the overall aerodynamic performance) via Fuzzy CODAS which enables to model uncertainty in order to overcome the physical effects that may arise in experiments. Thereby, a multi objective Taguchi methodology was applied for the overall aerodynamic performance with a novel Fuzzy logic based multi criteria decision analysis approach. As a result, Model-4, having tubercle design parameters of amplitude of 0.025c and 0.0125c and wavelength of 0.5c and 0.125c, was found to have the best performance with the novel Taguchi approach, which saves time and cost. In addition, it has been determined that the airfoils, Reynolds number and angle of attack are significant and what level of contribution to the overall aerodynamic performance. At this point, the most important control factor has emerged as the angle of attack.

Random flutter analysis of a novel binary airfoil with fractional order viscoelastic constitutive relationship

The fractional order model emerges naturally when the integer order model fails to meet practical requirements and finds extensive applications in engineering practice. However, there is still limited research on the random flutter of fractional order viscoelastic binary airfoils. This study aims to explore the random flutter of such airfoils under the influence of Gaussian white noise excitation by utilizing the pth moment Lyapunov exponent. Firstly, a two-degree-of-freedom fractional order stochastic dynamic equation is established for the viscoelastic binary airfoil through the introduction of fractional order damping. The singular perturbation method is then employed to derive the pth moment Lyapunov exponent of the system. An approximate analytical solution of the pth moment Lyapunov exponent is obtained through Fourier series expansion, which exhibits good agreement with numerical results obtained from Monte Carlo simulations. Subsequently, a comprehensive analysis is conducted to examine the impacts of fractional order, airflow velocity, noise intensity, and key structural parameters on the stochastic flutter of the fractional order viscoelastic binary airfoil. The findings indicate that compared with the typical binary airfoil model, the flutter speed of the fractional-order viscoelastic binary airfoil is significantly increased, the stability of the system is highly sensitive to the natural frequency of the system, and the fractional-order factor has a positive effect on the stochastic stability of the binary airfoil before the critical value. The above research results can guide the design optimization of the fractional-order viscoelastic airfoil.

High-Lift Aerodynamics of Integrated Distributed Propulsion Systems with Thrust Vectoring

Recent interest in distributed electric propulsion in aeronautics has motivated the exploration of novel approaches for integrating this technology into fixed-wing aircraft. Quasi-two-dimensional wind tunnel experiments were conducted with an aeropropulsive airfoil model, which included 10 integrated electric ducted fans and trailing-edge thrust vectoring capability. The experimental model was designed based on a reference aeropropulsive system originally optimized for transonic flight conditions. The model incorporated flow conditioners to separate the capture streamtubes of each fan and transition the circular internal flow into a rectangular nozzle exit. The system angle of attack, thrust coefficient, and nozzle deflection angle were all varied throughout the study. Surface pressure data, aggregate lift, drag, and pitching moment performance, and individual fan thrust data were all collected. Experimental results show an increased lift curve slope and maximum lift coefficient with larger fan thrust alongside larger aerodynamic contributions to drag and pitching moment. Deflection of hinged flaps to vector thrust reduces the airfoil zero-lift and stall angles of attack, similar to traditional trailing-edge flaps. Finally, thrust-drag bookkeeping methods demonstrate how jet momentum and airfoil aerodynamics interact. This experiment intends to highlight the aerodynamic mechanisms through which integrated propulsors couple with airfoils to achieve high-lift performance.

THE AIRCRAFT ENGINE PROPELLER MAIN CHARACTERISTICS DETERMINATION IMPROVED METHOD

An improved method of the fixed and variable pitch propeller aerodynamic characteristics determining that based on the vortex theory is presented. It is shown that the design of propellers has it`s peculiarities, it does not take into account a number of factors that affect the propeller operation to one or another degree. This actualized the special purpose unmanned aerial vehicles engines propellers aerodynamic characteristics calculating methodology improvement. Since the use of the propeller profiles performances in the design requires the air compressibility correction introduction already after the selection of the propeller, that complicates the design, therefore the mathematical model of the variable-pitch propeller working process has been improved based on the profile model with the correct consideration of the Mach and Reynolds numbers influence on the aerodynamic characteristics of the air screw. This advantage of the developed airfoil model allows the design and verification of a subsonic propeller for ground and flight operations. Methods of design and verification calculations of propeller blades are presented. Verification of the improved methodology was carried out by comparing calculated data with known experimental data. The reliability of the improved aircraft engine propeller main performances determination methodology is substantiated by the correct application of the numerical and experimental methods of aerodynamics, the consistency of theoretical provisions with experimental data. The satisfactory coincidence of the calculated data obtained by the improved method of the engine propeller main performances determination allowed us to draw a conclusion concerning its efficiency. The improved technique for the main performances of an aircraft engine propeller determination does not require knowledge on the propeller profiles aerodynamic characteristics from which the blade is drawn, since these characteristics are calculated based on known geometric data, taking into account the Mach and Reynolds numbers. This allows you to design and build a subsonic propeller of both fixed pitch and variable pitch.

Flow Development Over An SD7003 Airfoil At Different Accelerations From Rest

This work examines the effect of acceleration on the formation of a laminar separation bubble (LSB). The experiments were performed in a water towing tank with an SD7003 airfoil model accelerated from rest to a constant chord Reynolds number. Quantitative flow field measurements were performed using two-component time-resolved Particle Image Velocimetry (PIV) over a range of accelerations. A detailed analysis of the spatio-temporal flow development is conducted focusing on the LSB formation and dynamics. The results provide insight into the mechanism of LSB formation. The associated transient flow development is shown to persist over several convective time units after steady state free-stream velocity is reached, with no significant effect of acceleration on the overall transient duration. However, the acceleration rate has a substantial effect on flow development during the acceleration phase.

Dynamic stall modeling of wind turbine blade sections based on a data-knowledge fusion method

Dynamic stall often leads to unsteady load and performance degradation in horizontal axis wind turbines. Therefore, accurate modeling of dynamic stall is crucial. However, due to the large variations of the blade aerodynamic profiles and the complexity of dynamic stall flow, numerical simulation and wind tunnel experiment are costly. On the other hand, widely used semi-empirical models have limited accuracy. Hence, this paper proposes a data-knowledge fusion method that incorporates physical knowledge into a neural network to improve its accuracy and generalization ability. Firstly, the force components of the Leishman–Beddoes model are incorporated into the network. An efficient dynamic stall model for the S809 airfoil is thus established with a small amount of high-precision experimental data. It achieves extrapolation predictions of reduced frequency and angle of attack with only 1/5 of the samples in the database to train. Moreover, to make full use of the accumulated existing airfoil data to assist in modeling other airfoils, the obtained S809 model is fused in the network to predict the aerodynamics of S810 and S814. The average relative error of the prediction cases is nearly 10%. Comprehensively, this paper provides a new paradigm for assessing the dynamic stall of the wind turbine blade.

Wind Tunnel Tests of a Thick Wind Turbine Airfoil

ABSTRACTThis article reports about a wind‐tunnel experiment carried out in the ONERA F2 low‐speed wind tunnel on a model of the DU 97‐W‐300Mod airfoil designed for wind turbine application. The wind tunnel, the airfoil model, and experimental techniques used are presented, with special emphasis on the data processing and corrections required to derive airfoil forces and pressure distribution. To better document the flow physics at play, the results are illustrated by infrared thermography and surface oil flow visualization. The test allowed investigating Reynolds number effects between 1 and 3.8 millions. To ameliorate the understanding of the benefits and limitations of such airfoil testing, one section is devoted to the comparison of present results with previous experiments in other wind tunnels. Some of the difficulties arising in airfoil testing are evidenced and discussed to contribute to the improvement of test methods.