Airfoil Profile Research Articles

Prediction of the sound transmission loss of shape-varied sonic crystals: A transfer matrix approach.

This paper proposes a transfer matrix method (TMM) for modeling sonic crystals to predict the transmission loss of noise exiting an air extraction system. Because the crystals may be of different shapes (e.g., square, circular, or standardized airfoil profile to minimize airflow resistance) and must account for thermo-viscous losses, a discrete version of the TMM is used. Similar to the finite element method, a discretization of the geometry is first performed. Each element is modeled with a transfer matrix (TM) that includes the local thermo-viscous losses which attenuate the sound wave. For each element in parallel, the parallel TMM is employed. For the subsequently created elements in series, the classic TMM is used. This generates a global TM from which the sound transmission loss of the crystal network is deduced. The predictions obtained by the proposed method are compared to measurements in an acoustic tube for three different shapes of sonic crystals. The results show that a geometric tortuosity correction is necessary for the predicted bandgap center frequency to match the measurement. A correction is proposed, but this requires a possible refinement for more complicated profiles.

Aerodynamic performance characteristics of low Re airfoils: A parametric and multi criteria decision study

This research aims at investigating the aerodynamic performance of 51 low Re airfoils and applying a Multi Criteria Decision Making (MCDM) approach for selecting airfoils that align with the specific requirements of small wind turbines (SWTs). The study was carried out by varying the Re from 5 × 104 to 5 × 105; angle of attack (AOA) from −10° to 20°, thickness to chord ratio (0.1–0.9), camber ratio (0.1–0.9), and camber position (10 %–80 %) to evaluate the impact of these parameters on the airfoils’ performance. Furthermore, MCDM approach was applied to identify suitable airfoils optimized for their average lift to drag ratio, stall angle, operating range of AOA, strength, manufacturability, and material cost. The findings showed that of the teste parameters, the AOA and airfoil profile have the most pronounced effects on the airfoil performance. Among the tested airfoils, the E63 provided superior performance at 105 Re with LDR of 76.32, a 37.7 % improvement over that of NACA 4412 which is commonly used for wind turbine blade design. Furthermore, the MCDM results revealed that SG6043, FX63-137, E216 and E62 airfoils were the top-ranked airfoils suitable for SWTs application. These findings can help to produce optimized airfoil designs for increased performance and efficiency of SWTs.

Surrogate model based optimization of variable stiffness composite wingbox for improved buckling load with manufacturing and failure constraints

The buckling load of a wingbox is maximized by applying different automatic fiber placement (AFP) strategies on the skins of the wing having NACA 4412 airfoil profile. Specifically, the effect of single, dual and three region application of AFP on the optimal buckling load is studied to provide an outlook on the improvement of the optimal buckling load by increasing the number of skin panels, between rib stations, over which distinct reference fiber path definitions are made. Buckling load optimizations with manufacturing and failure constraints are performed via two different metaheuristic optimization algorithms to ensure that the global optimum reference fiber paths are obtained. For computational efficiency, separate radial basis function based surrogate models are generated for the buckling and the failure analysis. Our results show that the application of AFP separately with distinct reference fiber path definitions in each skin panel between the rib stations, the buckling load can be improved compared to the application of the AFP to a larger section of the wing skin. For the wingbox studied, compared to the wing with quasi-isotropic skins, 94% increase in the local buckling load of the root panel is obtained with the three region AFP application.

Performance enhancement of a semi-active flapping foil energy harvester via airfoil with modified trailing edge and jet flap

This paper aims to numerically study effectiveness of the use of a suitable combination of an airfoil with modified trailing edge and jet flap in enhancing the energy harvesting performance of a semi-active flapping foil. The configuration of the proposed airfoil is created by referring to the method of generating a blunt trailing edge airfoil. The most promising airfoil profile is obtained by only thickening the rear part of the original airfoil to reach a thickness of 2% chord, which can apparently promote the energy capturing capability of a semi-active flapping foil when compared with its conventional counterpart with a sharp trailing edge airfoil. Furthermore, a jet flap, an active flow control technique, is then applied on the aft portion of the modified airfoil and the effectiveness of this combination is assessed by a comparison with that of the passive flow control device, Gurney flap. The present findings suggest that this combination can be much more effective than a Gurney flap in significantly increasing the energy harvesting efficiency of the semi-active flapping foil over a wide range of operating conditions, and also has the advantage of structural integrity, which make it more suitable for harsh environment applications.

Hydrodynamic performance analysis of dual vertical axis turbine

Abstract This article adopts a biomimetic approach and uses the profile of the fastest sailfish in the ocean as the airfoil profile of a water turbine. Integrating centrifugal and axial flow turbines on one drive shaft can effectively integrate wave and current energy (wave current integration). The wake of a centrifugal turbine flows into the flow field of an axial flow turbine, and based on the Kantar effect, the energy harvesting coefficient of the axial flow turbine is improved. The five blades of the axial flow turbine and centrifugal turbine are subjected to uneven forces, resulting in torsional and radial forces on the drive shaft, causing periodic series motion of the turbine and reducing the overall lifespan of the machine.

Aero-propulsion coupling effects and installation characteristics of a distributed propulsion system

The ducted fan, as a quintessential propulsion device utilized in Distributed Electric Propulsion (DEP) aircrafts, exhibits a significant influence on the aero-propulsion coupling effects due to its installation characteristics on the wing. In this paper, we employed steady-state numerical analysis techniques in conjunction with actuator disk models and overset mesh to investigate aero-propulsion coupling effects and installation characteristics of a DEP configuration with 5 ducted fans distributed along the wing's trailing edge. We compared various conditions to the wing baseline airfoil under hover condition and cruise condition of the fan tip speed ratio λ from 1.44 to 4.32 and fan installation angle δT from 0 to 90°. The results indicate that DEP system affects the flow over the wing downstream of the maximum thickness point of the baseline airfoil profile at an installation angle of 0. A higher tip speed ratio the flow is accelerated in the upper surface region near the wing's trailing edge, whereas the low energy fluid fails to be accelerated at lower λ, instead forming a local flow blocking. With the increase of the fan installation angle, the overall system lift increases, but the thrust decreases, and both trends increase with the increase of the tip speed ratio. Specifically, the thrust provided by the distributed fans is reduced, and the inlet becomes one of the drag sources when the installation angle is high.

Comparative Analysis of Aerodynamic Efficiency in Small-Diameter Wind Turbine Blades: NACA 4412 vs. Clark Y

Objective: This study aims to compare the efficiency of the Naca 4412 and Clark Y airfoil profiles for small-diameter wind turbines using Solidworks® modeling, 3D printing, wind tunnel testing, and computational simulation. The hypothesis posits that the Naca 4412 will be more efficient. Theoretical Framework: Wind turbines convert the kinetic energy of wind into electrical energy, with the rotor being responsible for converting kinetic energy into mechanical energy, which is subsequently converted into electrical energy by the generator. Studies highlight the importance of optimizing the aerodynamics of the blades to maximize efficiency. Method: The Naca 4412 and Clark Y profiles were modeled in Solidworks® and 3D printed using high-quality ABS. The blades were tested in Armfield C15-10 and Edibon EEEC wind tunnels, measuring lift and drag forces at different angles of attack (30º to 70º) and varying wind speeds to achieve different Reynolds numbers. Results and Discussion: The Naca 4412 profile exhibited higher lift and drag compared to the Clark Y. At angles of 50º and 60º, both profiles showed greater efficiency, with the Naca 4412 achieving higher maximum angular velocity (357.93 RPM at 50º, 510.91 RPM at 60º). The performance difference can be attributed to the twist of the Naca 4412 and turbulence effects at low speeds. Research Implications: The results provide insights for the development of more efficient wind turbines, particularly in urban contexts where small wind turbines are used. Originality/Value: This study contributes by experimentally comparing two widely used airfoil profiles, offering valuable data for the optimization of small wind turbine blades.

Airfoil aerodynamic/stealth design based on conditional generative adversarial networks

Aerodynamic/stealth design is becoming an important factor in the advanced airfoil design. In this work, a supervised machine learning method is proposed for aerodynamic and stealth integrated airfoil design. The conditional generative adversarial network (CGAN) is constructed for the multidisciplinary design of airfoil. Then, the generator and discriminator simply using deep neural network have good robustness and stability in training. The CGAN model also shows good generalization capability in the test set, with less than 1% error in fitting to the airfoil profile data, and the generated airfoils are within 10% error compared to the test airfoil aerodynamic stealth characteristics. In addition, the optimization results based on the CGAN model demonstrate that aerodynamic performance improvement would increase the airfoil camber and stealth performance improvement would sharpen the airfoil leading edge.

Investigation on fixed pitch Darrieus vertical axis wind turbine

Small-scale Darrieus wind turbines have a wide scope in areas that are isolated from the power grid for such small-scale household applications. Applications of wind turbines on house roofs are one potential way to generate electricity from wind energy harvesting in low-wind urban locations. This work studies the aerodynamic behavior of a vertical axis wind turbine based on a MATLAB programming mathematical model. The NACA0021 airfoil profile blade was used in this present research investigation. The turbine was fabricated with dimensions such as chord length, c = 95 mm, blade height, h = 600 mm, and turbine diameter, D = 600 mm. The experimental results of the turbine for air velocity from 1 to 12 ms−1 were used in this paper and compared with analytical results. It has been observed that the fixed-pitch turbine does not start by itself at a low air velocity of 1 to 5 m/s due to a minimum and negative torque.

The Effects of a Seagull Airfoil on the Aerodynamic Performance of a Small Wind Turbine

Birds’ flight characteristics such as gliding and dynamic soaring have inspired various optimizations and designs of wind turbines. The implementation of biological wing geometries such as the airfoil profile of seabirds has improved wind turbine performance. However, the field can still benefit from further investigation into the aerodynamic characteristics of an inspired design. Therefore, this study evaluated the effect of a seagull airfoil design on the aerodynamic performance of the National Renewable Energy Laboratory (NREL) Phase VI wind turbine. By replacing its S809 airfoil with the laser-scanned profile of the seagull airfoil, the aerodynamic behavior at key locations of the NREL Phase VI wind turbine blade was numerically simulated in a three-dimensional environment using the Ansys Fluent 2022 R1 computational fluid dynamics (CFD) code. The results were validated against the experimental data, and analysis of the torque outputs, pressure distributions, and velocity profiles that were generated by both the baseline and modified models demonstrated the ability of the seagull airfoil profile to modify regions of minimum and maximum local velocities to achieve highly favorable pressure differentials, significantly increasing the torque output of the NREL Phase VI wind turbine by 350, 539, 823, and 577 Nm at 10, 15, 20, and 25 m/s inlet velocities, respectively.

Turbulence model study for aerodynamic analysis of the leading edge tubercle wing for low Reynolds number flows

A turbulence model study was performed to analyze the flow around the Tubercle Leading Edge (TLE) wing. Five turbulence models were selected to evaluate aerodynamic force coefficients and flow mechanism by comparing with existing literature results. The selected models are realizable k-ε, k-ω Shear Stress Transport (SST), (γ−Reθ) SST model, Transition k-kl-ω model and Stress- ω Reynolds Stress Model (RSM). For that purpose, the TLE wing model was developed by using the NACA0021 airfoil profile. The wing model is designed with tubercle wavelength of 0.11c and amplitude of 0.03c. Numerical simulation was performed at chord-based Reynolds number of Rec = 120,000. The Computational Fluid Dynamic (CFD) simulation reveals that among the selected turbulence models, Stress- ω RSM estimated aerodynamic forces (i.e. lift and drag) coefficients closest to that of the experimental values followed by realizable k-ε, (γ−Reθ) SST model, k-ω SST model and k-kl-ω model. However, at a higher angle of attacks i.e. at 16° & 20° k-ω SST model predicted closest drag and lift coefficient to that of the experimental values. Additionally, the critical observation of pressure contour confirmed that at the lower angle of attack Stress- ω RSM predicted strong Leading Edge (LE) suction followed by realizable k-ε, (γ−Reθ)SST model, k-ω SST model and k-kl-ω model. Thus, the superiority of Stress- ω RSM in predicting the aerodynamic force coefficients is shown by the flow behavior. In addition to this pressure contours also confirmed that k-kl-ω model failed to predict tubercled wing aerodynamic performance. At higher angles of attacks k-ω SST model estimated aerodynamic force coefficients closest to that of the experimental values, thus k-ω SST model is used at 16° & 20° AoAs. The observed streamline behavior for different turbulence models showed that the Stress- ω RSM model and k-kl-ω model failed to model flow behavior at higher AoAs, whereas k-ω SST model is a better approach to model separated flows that experience strong flow recirculation zone.

Numerical study on aerodynamic performance improvement and efficiency enhancement of the savonius vertical axis wind turbine with semi-directional airfoil guide vane

The growth of greenhouse gases increased the need for wind energy resource. Savonius vertical axis wind turbines (VAWT) have high potential as a turbomachine. Optimization methods such as flow injection on the rotor suction side to flow control on buckets developed as Savonius VAWTs operating range and efficiency are lower than other VAWTs. In this study, the semi-directional airfoil guide vane (SDAGV) was introduced to improve the aerodynamic performance and increase the efficiency of Savonius VAWT. The results indicate that the vane installation at the lower upstream of the rotor yields a power coefficient (Cp) of 0.12, representing a 140% growth compared to a single Savonius rotor. Furthermore, this installation extended the operating range of the turbine from a tip speed ratio (TSR) of 0.51–0.8. According to the results, it was found that more passages could improve efficiency. Five types of symmetrical airfoil profiles were evaluated for the guide vane. The NACA0010 airfoil profile, which has lower thickness than the others, obtained 7% higher efficiency than the base case consisting of NACA0012. Also, the optimal stagger angle for configurations NACA0021, NACA0018 was found to be 45°, and for NACA0010 and NACA0012 was determined to be 30°, respectively.

Improvement of Aerodynamic Performance of NACA 2412 Airfoil using Active and Passive Control Techniques

Improvement of Aerodynamic Performance of NACA 2412 Airfoil using Active and Passive Control Techniques

Numerical investigation of nitrogen spontaneous condensation over airfoils in cryogenic wind tunnel

Cryogenic wind tunnels (CWT) provide the aerodynamic tests that occur at high Reynolds numbers by operating under cryogenic environment to meet the requirements of hypersonic flight simulation. However, condensation in cryogenic environment near the limited condition destroys the reliability of the test measurement results. Accordingly, research on condensation in CWT is imperative for devising effective control strategies. This study introduces a transonic non-equilibrium condensation model, tailored to evaluate the complex phenomena of nitrogen condensation over airfoils. The model was applied to assess condensation effects on the NACA 0012–64 airfoil and the RAE 2822 airfoil under various operating conditions. Furthermore, the study examined the effect of the angle of attack and airfoil shape on the condensation process. The result show that nitrogen condensation near the airfoil is observable only under operating conditions within the pre-condensation zone. Operating conditions of CWT can be tailored to prevent condensation with specific airfoil profiles. The effect of condensation on the pressure coefficient includes advancing the position of the pressure jump and increasing the pressure coefficient of the airfoil intermediate region, particularly within the 20 %–70 % chord length span on the airfoil's upper surface. This primarily affects the measurement of lift coefficients in CWT. In the operating conditions of this study, the lift coefficient exhibits a maximum deviation of 31.4 %, and the drag coefficient shows a maximum deviation of 2.4 %. The transonic spontaneous condensation model offers an approach to evaluate condensation's impact on airfoil tests within CWT. The findings introduce a methodological framework for effectively controlling condensation phenomena.

Numerical analysis of a mini wind tunnel and experimental investigation of the mini wind tunnel utilizing a portable, three-axis load/balance measurement system

Investigation of a portable three-axis load/balance measurement system in a mini wind tunnel is the main subject of study. Firstly, a mini wind tunnel is designed, numerically analyzed and constructed. Then, measurements of lift and drag forces on a selected airfoil are carried out using data from the measurement system located in the test area. Tri-axis load/balance measurement system developed has a total of three load cells, one for drag and two for lift. Sensor data acquisition codes are written using Ardunio and force measurement experiments are performed at various angles of attack on the NACA2412 airfoil at Reynolds number of 60000, for the maximum flow rate of 5200 m3/h through fan controller in the constructed mini wind tunnel. After completing the mesh independence test, numerical studies are conducted in ANSYS Fluent for the same range of angles of attack using three different turbulence models. Realizable k-ε turbulence model gives more realistic high stall angles of attack than other turbulence models and similar to experimental results. In addition to the current experimental study, four other literature studies in similar Reynolds number ranges are used as reference cases. A visual study of the flow around the airfoil is given as velocity contours in addition to the numerical comparisons. From the numerical and experimental results, it is concluded that the NACA2412 airfoil profile wings are more efficient for moderate to high Reynolds numbers and the constructed load/balance measurement system and mini wind tunnel are highly successful in terms of lift and drag measurements.

Research on finite element model of rotor aerodynamicnoise in hovering state

The helicopter has been widely used in many fields, and the rotor aerodynamic noise has gradually attracted attention. The non-homogeneous wave equation, Ffowcs Williams-Hawkings equation (FW-H equation) derived from hydrodynamic N-S equation, combined with RANS turbulence simulation, was used to simulate the sound field of NACA0012 airfoil-shape model in hovering state. On this basis, by changing the thickness and camber of the blade, the aerodynamic noise of the rotor under different airfoil profile thickness and camber is calculated. The results show that the change of airfoil thickness and camber will affect the aerodynamic noise of the rotor in hovering state.

SCAMORSA-1: a camber-morphing wind turbine blade with sliding composite skin

Wind turbines form an increasingly important source of renewable and sustainable energy. Traditional rigid wind turbine blades are unable to control the flow of air over their surfaces, resulting in higher loads and lower aerodynamic efficiency at non-optimal wind speeds and angles of attack. This paper presents the design of SCAMORSA-1 (“Sliding CAmber- MORphing Skin Action”), a camber-morphing turbine blade in a Horizontal Axis Wind Turbine (HAWT) for increased aerodynamic efficiency and improved extreme load alleviation. The blade is linearly tapered and comprises three sections: a conventional rigid section, a morphing section, and a fixed blade tip, all covered by functionally graded composite skin. Measured from the root, the rigid section spans 0%-60% of the total blade length and its profile transitions at 20% from SD7062 thick airfoil to the thinner SD7037 airfoil. The rigid section includes carbon fiber composite spars that resist flap-wise bending. The morphing section occupies the next 30% of the span with SD2030 airfoil profile and can seamlessly change camber angle up to 10°. This section is composed of three hybrid ribs connected via two leading-edge composite spars and a trailing-edge synchronizing rod. Each hybrid rib has a solid leading-edge segment connected to a flexible trailing-edge segment via T-slots. The trailing-edge segment, where morphing occurs, is an enhanced version of the corrugated FishBAC design, with hexagonal honeycomb infill that increases the out-of-plane stiffness and allows for morphing deformation without internal buckling. Two of these hybrid ribs have servomotors housed in the leading-edge segment. These integrated actuators in the hybrid ribs actuate flexible carbon fiber ribbons that run through slits in the trailing-edge segment to morph it. At the trailing-edge portion of the morphing section, the composite skin transitions to a thin flexible layer that can slide over the deforming trailing-edge segment via skin sliders. Computational simulations were performed to quantify the performance gains and ensure safe operation of all components. A proof-of-concept model of SCAMORSA-1’s morphing section was manufactured and tested to demonstrate the effectiveness of the design.

Aeroacoustic investigation of a ducted wind turbine employing bio-inspired airfoil profiles

Ducted wind turbines for residential purposes are characterized by a lower diameter with respect to conventional wind turbines for on-shore applications. The noise generated by the rotor plays a significant role in the overall aerodynamic noise. By making modifications to the blade sections of the wind turbine, we can alter the contributions of aeroacoustic noise sources. This study introduces innovative wind turbine blade designs inspired by owl wing characteristics, achieving significant noise reduction without compromising aerodynamic performance. A three-dimensional scan of an owl wing was first employed to derive a family of airfoils. The airfoils were employed to modify the blade of a referenced wind turbine airfoil section at various positions on the blade span to determine a blade operating more efficiently at the tip-speed ratio of the original one. While maintaining the same aerodynamic performance, the bio-inspired profiles show a more uniform pressure coefficient distribution, considerably decreasing in the noise level. Furthermore, this study makes considerable progress in ducted wind turbine design by obtaining an 8 dB noise reduction and a 12% improvement in sound pressure level. An in-depth aerodynamic examination shows a 6.4% rise in thrust force coefficient and optimized power coefficients, reaching a peak at a tip speed ratio of 8, demonstrating improved energy conversion efficiency. The results highlight the dual advantage of the innovative design: significant noise reduction and enhanced aerodynamic efficiency, offering a promising alternative for urban wind generation.

Equivalent plate model of shape memory polymer composite based variable height corrugated structure

In this work, an equivalent plate model for a shape memory polymer composite based corrugation structure with varying height, for morphing application, is developed. A thermodynamically consistent constitutive relation based on temperature dependent phase transformation concept for shape memory polymer matrix is used in the composite model. The homogenization model is based on the equivalence of strain energy of a representative unit volume. Following validation, as an application, commonly used airfoil profile NACA 63210 was considered to demonstrate the model utility. Parametric studies have been undertaken to investigate the influence of corrugation parameters like thickness and number of corrugations.

An aero-structure-acoustics evaluation framework of wind turbine blade cross-section based on Gradient Boosting regression tree

Under the rapid development of wind turbines, the rotor size has substantially increased in recent years. To meet the key design criteria, finding a trade-off between aerodynamic, structure and noise (ASN) impact becomes a challenging problem. The blade cross-section is the basic element of the blade, its outer contour is the airfoil profile that produces aerodynamic loads as well as noise, and the inner part is the supporting composite material that provides enough stiffness to balance the loads. Modifying local blade sections can adjust the rotors’ overall performance. However, in the work of blade-combined ASN optimization, the iterative process using traditional numerical simulation methods becomes extremely heavy. In this study, a sustainable database is created based on a large number of calculations of aerodynamic, structural and noise attributes at various cross-sections. Then a platform named AFML (Airfoil machine learning) for simultaneously predicting the comprehensive performance of the cross-section is constructed by using the integrated Gradient Boosting Regression Tree algorithm. Results show that the prediction accuracy of AFML is acceptable even for unseen inflow conditions. By calling the pre-trained AFML, ASN data of the cross-section can be immediately obtained, and the blade shape and inner structure can be updated quickly.