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To investigate the impact of airfoil angle of attack on the output performance of a valveless piezoelectric pump with airfoil baffles, this study conducted comprehensive performance tests and full-flow field simulations of piezoelectric pumps across a range of angles. At a driving voltage of 100 V and with a Clark Y airfoil set at an angle of 0°, the piezoelectric pump reached a peak output flow rate of 200.7 mL/min. An increase in the angle of attack corresponded to a decline in both the maximum output flow rate and the maximum back pressure of the pump. Flow field simulation results demonstrated that an increased airfoil angle of attack led to a gradual increase in entropy production within the piezoelectric pump. Turbulent dissipation and wall entropy production were found to be more pronounced compared to viscous entropy production. High turbulent dissipation was primarily observed at the pump chamber inlet, the trailing edges of the airfoils in both the inlet and outlet pipes, and the outlet bend. As the angle of attack increased, the complexity of the vortex core structures within the flow field escalated as well. Regions with significant wall entropy production were notably concentrated at the outlet bend. [ABSTRACT FROM AUTHOR]

The shape of the blade strongly influences the aerodynamic behavior of wind turbines; therefore, it is essential to optimize its design to maximize the energy harvested from the wind. Some works address this optimized design problem using CFD, a tool that requires a lot of computational resources and time and starts from scratch. This work describes a new automated design method to generate aerodynamic profiles of wind turbines using existing blades as a base, which speeds up the design process. The optimization is performed using heuristic techniques, and the aim is to improve the characteristics of the blade shape which impact resilience and durability. Specifically, the glide ratio is maximized to capture maximum energy while ensuring specific design parameters, such as maximum thickness or optimal angle of attack. This methodology can obtain results more quickly and with lower computational cost, in addition to integrating these two design parameters into the optimization process, aspects that have been largely neglected in previous works. The analytical model of the blades is described by a class of two-dimensional shapes suitable for representing airfoils. The drag and lift coefficients are estimated, and a metaheuristic optimization technique, genetic algorithm, is applied to maximize the glide ratio while reducing the difference from the desired design parameters. Using this methodology, three new airfoils have been generated and compared with the existing starting models, S823, NACA 2424, and NACA 64418, achieving improvements in the maximum lift and maximum glide ratio of up to 13.8% and 39%, respectively. For validation purposes, a small 10 kW horizontal-axis wind turbine is simulated using the best design of the blades. The comparison with the existing blades focuses on the calculation of the generated power, the power coefficient, torque, and torque coefficient. For the new airfoils, improvements of 6.7% in the power coefficient and 5.5% in the torque coefficient were achieved. This validates the methodology for optimizing the blade airfoils. [ABSTRACT FROM AUTHOR]

Wind turbine blades have the working principle of converting wind energy into mechanical energy. The shape of the blade is influenced by the profile of the airfoil which has aerodynamic characteristics in the form of a moment coefficient (CM) that affects the performance of the aerodynamic force produced by the blade. This study aims to analyze the performance of H-Rotor wind turbine blades with NACA 0018, SELIG 1210, and FX 63-137 airfoil types using the Blade Element Theory method. The research method was carried out by testing the aerodynamic characteristics of airfoils in an open-circuit wind tunnel at a wind speed of 7.2 m/s. The analysis method was carried out by analyzing the drag force (FD), lift force (FL), normal force (FN), tangential force (FT) produced by each blade position. The position of the blade is influenced by the azimuth angle (θ) contained in each H-Rotor type wind turbine blade so that the value of the angle of attack changes at each blade position. The results of the analysis explain that tangential force affects the torque and power to be produced. The novelty of this study lies in a systematic approach in selecting the optimal airfoil based on a comprehensive analysis of aerodynamic forces, with a special focus on the comparison of air characteristics in various blade positions. The selection of NACA 0018 airfoil with an initial installation attack angle of 15° produces an average tangential force over one revolution of 502.2 Newtons, making it the right choice to use in a 3-blade H-Rotor wind turbine. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Multiple engineering projects have confirmed that hydraulic machinery operating in sediment-laden rivers undergoes sediment abrasion. Guide vanes are among the most severely worn flow-passing components and have long been a key research focus in hydraulic machinery. In this research, a wear test of the NACA0012 cascade under a 10° incoming flow angle was carried out in the Venturi test system, and the evolution process of the wear was analyzed. The three-dimensional flow channel of the cascade was constructed, and the Finnie wear model was adopted for computational fluid dynamics (CFD) simulations to analyze the wear mechanism at the initial stage. The results indicate that abrasion primarily occurs at the airfoil's leading edge and progresses through three stages: initiation, development, and stabilization. The calculated results closely matched the latest wear outcomes: In the initial stage, the wear rate density was influenced by the particle impact velocity, angle, volume fraction, and y-direction shear stress. A low-velocity zone near the impact point, combined with rebounding particles causing secondary impacts, increases the particle volume fraction and wear rate density. These secondary impacts are the primary causes of erosion on both the upstream and downstream surfaces. Furthermore, flow separation downstream from the leading edge makes this region highly susceptible to wear. This study provides valuable insights for addressing wear in hydraulic machinery for practical engineering applications. [ABSTRACT FROM AUTHOR]

Dynamic stall is a serious phenomenon that restricts aeronautical vehicles' maneuverability. It happens on the blades as their angle of attack increase, especially on the blade of wind turbines. In this paper, two airfoils are investigated in actual conditions. To alleviate dynamic stall the geometries of the airfoils are modified by drooping and rounded leading-edge tip method and also combination of both. To study the effect of the modifications, the unsteady flow fields around the pitching airfoils, numerically simulated using URANS. Results illustrates, in addition to alleviate dynamic stall, the methods enhance aerodynamic characteristics by reducing drag force and preventing sudden jump of lift force, especially at the maximum angle of attack. Finally, a detailed investigation is conducted on the flow behavior around the airfoil to discover the supporting physics behind the improvements made by the present methods. Which revealed that these two passive methods, aim to prevent the formation of leading-edge vortex on the airfoil which finally delays the dynamic stall. [ABSTRACT FROM AUTHOR]

To overcome the technical challenges of the multi-blade centrifugal fan, such as low efficiency and insufficient total pressure, the blades of the fan were optimally designed in this study. The flow field of the multi-blade centrifugal fan with a single-arc blade and an airfoil blade was simulated and compared using Computational Fluid Dynamics (CFDs). Under steady-state conditions, the total pressure, velocity field distribution, and aerodynamic performance of a multi-blade centrifugal fan were analyzed. The numerical results showed that there were vortices, secondary flows, and boundary layer separation phenomena in the flow passage of the single-arc multi-blade centrifugal fan. Based on the lift-to-drag ratio theory of airfoil in aerodynamics, four different airfoil blades were designed for the multi-blade centrifugal fan. The study found that the lift-to-drag ratio of the airfoil blades was positively correlated with the fan efficiency; among them, the A-type airfoil exhibited the highest lift-to-drag ratio within the 0–10 degree angle of attack range. The three-dimensional simulation results indicated that, except for the initial operating point B, the A-type airfoil showed higher fan efficiency under other operating conditions, and its total pressure curve was the most stable. In addition, the use of airfoil blades effectively suppressed the aforementioned adverse flow phenomena and improved the flow within the blade passage. Experimental verification further confirmed the effect of airfoil blades on improving fan performance: compared to single-arc blades, the efficiency of the multi-blade centrifugal fan increased by 3–7% after using airfoil blades, and the upper limit of high-efficiency flow increased from 450 m3/h to 650 m3/h. Meanwhile, the total pressure and power of the airfoil fan were also significantly improved. The results of this work are significant for guiding the optimal design of the fan. [ABSTRACT FROM AUTHOR]

Corrections for wind tunnel experimental results are crucial when accounting for tunnel wall interference. This study introduces a new method, the non-uniform wall pressure signature method (NUWPSM), which is designed to address tunnel wall interference in airfoil. The improved wall pressure signature method (WPSM), an enhanced version of the WPSM, is developed to address the velocity disparities and systematic errors in pressure measurements between with and without model conditions. Furthermore, the NUWPSM considers the non-uniformity of the flow induced by the limited far-field effect in wind tunnel experiments. Utilizing experimental data from three different scaled models of the WA210 airfoil, the efficacy of both the Improved WPSM and NUWPSM is verified. Results indicate that the Improved WPSM exhibits superior capabilities in simulating the distribution of axial induced velocity along the wall compared to the traditional WPSM. Additionally, both the Improved WPSM and NUWPSM demonstrate comparable abilities in correcting tunnel wall interference, achieving precise corrections within an angle of attack range of −180° to +180°. Notably, the NUWPSM effectively captures the velocity non-uniformity induced by the limited far-field effect, thereby extending its applicability to a broader range of scenarios. Furthermore, the NUWPSM showcases enhanced robustness by eliminating human intervention in the singularity quantity and distribution. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review of the studies and research conducted on flow separation control on lifting surfaces. In this paper, two critical parameters, namely, the momentum coefficient and excitation frequency, that significantly impact flow separation control are analyzed in detail. Through a comprehensive literature review, experimental and numerical studies are examined in order to gain insight into the underlying mechanisms of momentum injection and excitation frequency on the shear layer and wake dynamics and to quantify the impact of these parameters on the flow separation control. Effective flow control on lifting surfaces can modify the streamlines and pressure distribution, thereby increasing their aerodynamic efficiency. This paper focuses on the control of flow separation on airfoils, with particular attention paid to the benefits of such control, including lift enhancement, drag reduction, aerodynamic efficiency enhancement, performance enhancement, and other important features. This paper presents a review of studies that have employed blowing actuators, as well as zero net mass flux, plasma, and acoustic actuators, in order to provide an appropriate historical context for recent developments. The findings of this review paper will contribute to a better understanding of the optimal conditions for efficient flow separation control on lifting surfaces using unsteady excitation, which can have significant implications for improving the performance and efficiency of various aerodynamic applications. This paper aims to elucidate and emphasize the positive and negative aspects of existing research, while also suggesting new interesting areas for future investigation. [ABSTRACT FROM AUTHOR]

The current straw micro-crusher is often utilized within a circular crushing chamber, leading to the formation of a circulation layer that impacts the efficiency of crushing. This study proposes an airfoil crushing chamber to disrupt the circulation layer and modify particle motion characteristics. Based on CFD-DEM analysis with flow field characteristics, motion trajectory, crushing rate, motion speed, and force magnitude as evaluation indices, the crushing performance and flow field distribution of both chamber types are compared. Test results indicate that the airfoil crushing chamber outperforms the circular one, thereby validating the accuracy of the theoretical and numerical analyses. [ABSTRACT FROM AUTHOR]

In recent years, leading-edge tubercles have gained significant attention as an innovative biomimetic flow control technique. This paper explores their impact on the aerodynamic performance and flow patterns of an airfoil through wind tunnel experiments, utilizing force measurements and tuft visualization at Reynolds numbers between 2.7 × 105 and 6.3 × 105. The baseline airfoil exhibits a hysteresis loop near the stall angle, with sharp changes in lift coefficient during variations in the angle of attack (AOA). In contrast, the airfoil with leading-edge tubercles demonstrates a smoother stall process and enhanced post-stall performance, though its pre-stall performance is slightly reduced. The study identifies four distinct flow regimes on the modified airfoil, corresponding to different segments of the lift coefficient curve. As the AOA increases, the flow transitions through stages of full attachment, trailing-edge separation, and local leading-edge separation across some or all valley sections. Additionally, the study suggests that normalizing aerodynamic performance based on the valley section chord length is more effective, supporting the idea that leading-edge tubercles function like a series of delta wings in front of a straight-leading-edge wing. These insights provide valuable guidance for the design of blades with leading-edge tubercles in applications such as wind and tidal turbines. [ABSTRACT FROM AUTHOR]

Small wind turbines (SWTs) can generate sufficient electricity to meet the energy needs of developing countries. However, due to the airflow characteristics at low Reynolds numbers and associated issues, specific airfoil designs are crucial to define the blade geometry. In this study, the lift coefficient (CL), stall angle of attack (AoA), and lift-to-drag coefficient ratio (CL⁄CD) of S1048, S3021, and S5010 airfoils and then optimized shapes with various thickness-to-camber ratio percentages (t/c%) were analyzed using XFOIL software to optimize their suitability for SWT applications. The aerodynamic efficiency of the optimized airfoils in terms of CL, drag coefficient (CD), CL/CD, and stall AoA was evaluated across Reynolds numbers ranging from 50,000 to 500,000. The findings revealed that these modified airfoils exhibited peak CL⁄CD values surpassing those of their baseline airfoils for the Reynolds number range of 50,000–500,000. The magnitudes of these improvements varied for each airfoil and at different Reynolds numbers. Additionally, the geometric modifications in terms of t/c% applied to the S1048, S3021, and S5010 airfoils resulted in enhanced maximum CL and stall AoA across all analyzed Reynolds numbers. [ABSTRACT FROM AUTHOR]

Copyright of Karaelmas Science & Engineering Journal / Karaelmas Fen ve Mühendislik Dergisi is the property of Karaelmas Science & Engineering Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aerodynamic stealth design is a key technology for aircraft to realize efficient combat in high-risk environments，and it has been a hot technology researched by aviation powers for a long time. This paper combines the group's many years of experience in aerodynamic stealth design and the demand for aerodynamic stealth design in recent years，summarizes and analyzes the development history and current research status of the aerodynamic stealth design of overall aerodynamic layout，the aerodynamic stealth design of wing and the aerodynamic stealth design of air intake and exhaust system. According to the current research status，three key technologies for comprehensive and optimal aerodynamic stealth design are sorted out：efficient parameterization technology for complex shape， aerodynamic stealth refinement design technology，and integrated aerodynamic stealth design technology for internal and external flow. Finally，combined with the design requirements of aerodynamic stealth for future aircraft， four key research directions are expected：aerodynamic electromagnetic infrared integrated stealth design，aerodynamic stealth design considering coating，aerodynamic/stealth structure integrated design，and active flow control stealth integrated design.

Abstract Corrections for wind tunnel experimental results are crucial when accounting for tunnel wall interference. This study introduces a new method, the non-uniform wall pressure signature method (NUWPSM), which is designed to address tunnel wall interference in airfoil. The improved wall pressure signature method (WPSM), an enhanced version of the WPSM, is developed to address the velocity disparities and systematic errors in pressure measurements between with and without model conditions. Furthermore, the NUWPSM considers the non-uniformity of the flow induced by the limited far-field effect in wind tunnel experiments. Utilizing experimental data from three different scaled models of the WA210 airfoil, the efficacy of both the Improved WPSM and NUWPSM is verified. Results indicate that the Improved WPSM exhibits superior capabilities in simulating the distribution of axial induced velocity along the wall compared to the traditional WPSM. Additionally, both the Improved WPSM and NUWPSM demonstrate comparable abilities in correcting tunnel wall interference, achieving precise corrections within an angle of attack range of −180° to +180°. Notably, the NUWPSM effectively captures the velocity non-uniformity induced by the limited far-field effect, thereby extending its applicability to a broader range of scenarios. Furthermore, the NUWPSM showcases enhanced robustness by eliminating human intervention in the singularity quantity and distribution.

This work provides direct experimental evidence supporting the generation of the airfoil circulation associated with a starting vortex as a viscous-flow process based on global velocity measurements near the trailing edge (TE) of a NACA0012 airfoil at the angle of attack of 6° in a low-speed wind tunnel. The evolving flow topology near the TE exhibits the apparent inviscid flow pattern in a very short initial period, the sequential formation and growth of the starting vortex as a result of near-wall viscous flow development, and the final establishment of the Kutta condition as the starting vortex travels downstream. The evolving flow field in the starting flow over the airfoil is topologically consistent. [ABSTRACT FROM AUTHOR]

ObjectivesA multi-objective optimization algorithm is proposed to address the problem of the complex operating conditions of large horizontal axis hydraulic turbine blades. MethodsAn airfoil optimization model is established based on the multi-island genetic algorithm, the airfoil is parametrically fitted using the class shape function transformation (CST) function method, and the whole optimization process is integrated on the Isight platform to achieve automatic optimization. ResultsUsing the above method, NACA 63813/63815/63816 airfoils are selected as the initial airfoils for multi-objective optimization, CFD numerical validation is carried out on the obtained airfoils using the Fluent turning model, and the lift-to-drag ratios and lifting forces at the airfoil attack angle of 5° are selected as the optimization objectives, resulting in the optimized airfoils gaining increased lift coefficients of 14%, 15% and 20%, and increased lift-to-drag ratios of 14%, 16% and 28%, respectively. ConclusionsNumerical validation shows that the lift-to-drag ratios of the optimized airfoil is higher than those of the original airfoils with the same thickness under several operating conditions, and the structural strength of the blade is improved while ensuring good aerodynamic performance, making it more suitable than conventional airfoils for large-scale tidal current energy horizontal axis hydraulic turbines.

The theory of aircraft icing and its disaster mechanisms are crucial for preventing icing accidents and enhancing flight performance. The research progress on the flow field characteristics under different icing conditions and special wing configurations are systematically summarized in this paper. It is pointed out that, the actual three-dimensional ice shapes are complex, have multiple structural features, and coupling mechanisms with separated flow and turbulence structures should be further studied. The aerodynamic performance analysis of special wings under supercooled large droplet conditions is the significant future research direction. Turbulence field analysis focuses on identifying instability characteristics of the icing wing flow field and multi-scale structural interaction mechanisms. Exploring the ice-flow coupling mechanism is of reference value for developing multi-factor, multi-parameter, and multi-scale icing prediction and computational models.

The elastic surface algorithm (ESA) is an iterative inverse design method for airfoils, considering the airfoil wall as an elastic curved beam pinned at its beginning and ending points. This structure deforms in response to the disparity between existing and target pressure distributions. This paper introduces an improvement to the ESA, allowing controlled movement of the airfoil's leading edge within a vertical groove. This advancement enables the adjustment of the angle of attack during the inverse design process, enhancing the airfoil's robustness and flexibility. In contrast to a fixed angle of attack approach, the proposed method prevents unrealistic geometric features, such as airfoil fishtailing, improving convergence potential. The developed method was validated through the inverse design of NACA0012 and FX63-137 airfoils in a viscous subsonic flow regime. The flow solver was validated using existing experimental results, showing good agreement. Finally, the pressure distribution of the FX63-137 airfoil was modified to increase lift or decrease drag. The corresponding geometries were obtained via the advanced ESA method, resulting in an almost 4 % increase in the lift-to-drag ratio. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to define new simple shape descriptors to analyze airfoils. The ImageJ platform is used to calculate twelve different shape descriptors such as area, convex hull, contour temperature and solidity by performing image processing. One of the most important findings is that an increase in the thickness of an airfoil leads to corresponding increases in its area, perimeter, area of minimum enclosing area, and convex hull area. Another noteworthy discovery is that the values derived from these basic features, either increasing or decreasing. Simple shape features in the study are not used independently, as they do not possess distinct characteristics that set them apart from one another. Machine learning and deep learning applications can achieve greater success when these features are combined with other elements. The combination of these features with other shape attributes, such as chain code histograms, shape signatures, and central moments, can enhance the success of machine learning and deep learning applications. [ABSTRACT FROM AUTHOR]

This paper experimentally and numerically investigates the effects of suction side surface roughness on the aerodynamic performances of the NACA 0015 turbine blade profile. Three different NACA 0015 turbine blade configurations, which are smooth (K0), single roughness (K1), and double roughness (K2), are considered. The experimental studies were conducted using the HM-170 GUNT open wind tunnel model. The aerodynamic characteristics of these three blade configurations are evaluated in terms of their lift coefficient (CL), drag coefficient (CD), and aerodynamic efficiency (CL/CD). The maximum CL (CL,max) for K0 was obtained at 25°, whereas the CL,max angles for the K1 and K2 roughness blade profiles were reduced to 22.5°, utilizing the rough surfaces on the suction side. The experimental analysis revealed that the K2 profile demonstrated a 21% and 19% enhancement in maximal CL over the K0 and K1 profiles, respectively. The highest CL/CD was observed with K1, except at low attack of angle (aoa), where the smooth blade profile resulted in slightly better performance. Experimental analysis showed peak CL/CD at aoa of 7.5° for K0, and 12.5° for both K1 and K2, with K1's optimal CL/CD being 2.85% and 8.5% higher than K0 and K2, respectively. Numerical analysis indicated that the CL/CD,avg for K1 was observed to be 11% and 8% higher than that of K0 across all aoa. [ABSTRACT FROM AUTHOR]

The effects of the erosion present on the leading edge of a wind turbine airfoil (DU 96-W-180) on its aerodynamic performances have been investigated numerically in the framework of a SST k–ω turbulence model based on the Reynolds Averaged Navier-Stokes equations (RANS). The results indicate that when sand-induced holes and small pits are involved as leading edge wear features, they have a minimal influence on the lift and drag coefficients of the airfoil. However, if delamination occurs in the same airfoil region, it significantly impacts the lift and resistance characteristics of the airfoil. Specifically, as the angle of attack grows, there is a significant decrease in the lift coefficient accompanied by a sharp increase in the drag coefficient. As wear intensifies, these effects gradually increase. Moreover, the leading edge wear can exacerbate flow separation near the trailing edge suction surface of the airfoil and cause forward displacement of the separation point. [ABSTRACT FROM AUTHOR]

The focus of this research was on the equivalent particle roughness height correction required to account for the presence of ice when determining the performances of wind turbines. In particular, two icing processes (frost ice and clear ice) were examined by combining the FENSAP-ICE and FLUENT analysis tools. The ice type on the blade surfaces was predicted by using a multi-time step method. Accordingly, the influence of variations in icing shape and ice surface roughness on the aerodynamic performance of blades during frost ice formation or clear ice formation was investigated. The results indicate that differences in blade surface roughness and heat flux lead to disparities in both ice formation rate and shape between frost ice and clear ice. Clear ice has a greater impact on aerodynamics compared to frost ice, while frost ice is significantly influenced by the roughness of its icy surface. [ABSTRACT FROM AUTHOR]

A Zonal Detached Eddy Simulation (ZDES) based on the SST turbulence model is implemented to the numerical investigation of the trailing edge stall of a LS-0417 airfoil, which includes multiple DES modes for different classifications of flow separation and adopts the subgrid scale definition of Δ ω . The entire stall process under a series of AOA is simulated according to the experiment condition. The performance of URANS and ZDES in the prediction of the stall flow field are compared. The results reveal that the stall point obtained through ZDES is consistent with the experiment; the deviation of the predicted maximum lift coefficient from the measured result is only 0.8%, while the maximum lift is overpredicted by both RANS and URANS. The high frequency fluctuations are observed in the time history of the lift in ZDES result during stall. With the increase in the AOA, a mild development of separation and a gradual decrease in leading edge peak suction are manifested in the ZDES result. The alternate shedding of shear layers and the interference between the leading edge and trailing edge vortices are illustrated through ZDES near the stall point; the corresponding turbulent fluctuations with high intensity are captured in the separation region, which indicates the essential difference in the prediction of stall process between URANS and ZDES. [ABSTRACT FROM AUTHOR]

Small wind turbines operating in low wind speed regions have not had any significant success. In addition, small wind speed regions occupy a large area of the world, so they represent a potential area for installing small wind turbines in the future. In this paper, a method to design an efficient airfoil for small wind turbines in low wind speed conditions using XFLR5 and CFD simulations is implemented. Because the impact of the airflow on the blade surface under low Re number conditions can change suddenly for small geometries, designing the airfoil shape to optimize the aerodynamic performance is essential. The tuning of the key geometric parameters using inversion techniques for better aerodynamic performance is presented in this study. A two-dimensional model was used to consider the airflow on the airfoil surface with differences in the angle of attack. The original S1010 airfoil was used to design a new airfoil for increasing the aerodynamic efficiency by using V6.57 XFLR5 software. Subsequently, the new VAST-EPU-S1010 airfoil model was adjusted to the maximum thickness and the maximum thickness position. It was simulated in low wind speed conditions of 4–6 m/s by a computational fluid dynamics simulation. The lift coefficient, drag coefficient, and CL/CD coefficient ratio were evaluated under the effect of the angle of attack and the maximum thickness by using the k-ε model. The simulation results show that the VAST-EPU-S1010 airfoil achieved the greatest aerodynamic efficiency at an angle of attack of 3°, a maximum thickness of 8%, and a maximum thickness position of 20.32%. The maximum value of CL/CD of the new airfoil at 6 m/s was higher than at 4 m/s by about 6.25%. [ABSTRACT FROM AUTHOR]

Transonic buffet flow is a classical complex and unstable flow that has a negative effect on aircraft fly safety. Therefore, it is crucial to study the unsteady characteristics of buffet flow. The numerical analysis method is very useful in achieving the aforementioned goal. In this paper, focused on the typical supercritical airfoil OAT15A in fixed and pitching conditions, unsteady Reynolds averaged Navier–Stokes (URANS) closed with the sst-kω turbulence mode, coupled with the structure dynamical equation, is utilized to investigate the transonic buffet flow. Firstly, from the perspective of coherent flow structure, flow velocity divergence snapshots constructed from unsteady flow solutions are used to analyze the feature of transonic buffets in the two cases mentioned. Then, DMD modes are extracted by the dynamic mode decomposition technique from the velocity snapshots and adopted to analyze the flow modes of the two distinct flow fields. The numerical simulation results show that, in the fixed case, the regular motion feature of the buffet is present, the shock oscillation is closely related to the vortex structure, and the durations of rearward and forward movements of the shock are both equal to half of the buffet period. In the pitching case, the duration of the rearward motion of the primary shock is approximately five eighths of one buffet period, and the secondary shock appears with the primary one moving downstream, and they interact with each other. The region of the shock movement is larger than that of the fixed case, and there is chaotic flow rather than periodic flow in its wake. Structural elastic oscillation changes the characteristics of the aerodynamic response, which is solely affected by the frequency of the pitching oscillation. [ABSTRACT FROM AUTHOR]

Vehicles that use the principle of dynamic ground effect principle are innovative vehicles that have prospects for use as high-speed unmanned vehicles. It is known that when an aircraft moves near the ground, the phenomenon of increasing lift occurs, which allows for contactless movement at high speeds. However, the effectiveness of this ground effect depends on the airfoil shape. The object of this study is the aerodynamic processes that occur during the movement of an unmanned aerial vehicle near the ground. The influence of the effect of approaching the ground on the aerodynamic characteristics of four airfoil of different shapes has been considered: Clark YH-12, NACA-M6, USA-35B, TsAGI-721, which are used in subsonic highspeed aircraft, including unmanned aerial vehicles. The aim of the work is to evaluate the performance of these aerodynamic airfoils in near-surface operation and to determine the most promising shape for use in small unmanned WIGs. CFD modeling methods were used as a research tool. The pressure and velocity fields around the wing airfoils were determined and the influence of the distance to the ground and the angle of attack on the aerodynamic characteristics was established. It was found that the best aerodynamic quality for all airfoils is achieved at angles of attack of 4–6°. It is not recommended to use airfoils with angles of attack close to 0° as the ground may have a negative effect on lift. The USA-35B airfoil demonstrated the greatest increase in aerodynamic quality when approaching the surface, with a maximum increase of 67 %. This makes it possible to recommend USA-35B as small unmanned aerial vehicles with a dynamic ground effect principle [ABSTRACT FROM AUTHOR]

Wind turbines installed in regions with high altitudes and low temperatures on winter season, ice can accumulate on the blade surfaces during operating condition. A small amount of ice accretion on the blade surface can result in several crucial issues, such as AEP (annual energy production) reduction due to degrade aerodynamic performance, and safety concerns related to ice falling down. Predicting and elucidating icing accretion phenomena under various weather conditions are significantly essential in the aspect of operating and maintenance. The primary objective of this study was to assess the impact of ice accretion on the aerodynamic characteristics of wind turbine blades CFD (computational fluid dynamics) analysis, including ice thickness and shape, under varying weather conditions. Therefore, this study focused on identifying the aerodynamic characteristics affected by ice accretion, including ice thickness and shape under various weather conditions through Fensap. Through this methodology, the presence of ice accumulation on the blade surfaces was investigated, and its adverse impact on aerodynamic performance has been assessed. [ABSTRACT FROM AUTHOR]

Generating more usable power annually from the river and tidal currents is essential to improving cost-effectiveness. Among various alternative options, the performance improvement of the blade foil has been considered in this work. When the fluid over the blade surface loses kinetic energy, flow separation occurs. The lift forces are reduced by flow separation, which finally results in less power production by the horizontal axis current turbine. To extract more power, it is necessary to overcome this flow separation. This paper presents a passive flow control method using tubes at regular intervals on the blade section to improve its performance considering its application on a horizontal axis current turbine. The tube inlet and outlet positions are determined by analyzing the force coefficients, glide ratio, and stall angle for a specific angle of attack. Finally, the performance characteristics are compared between the baseline and the modified hydrofoil. The maximum lift coefficient of the hydrofoil is increased by 15.7%. Also, the maximum glide ratios are considerably increased beyond the stall of the baseline profile. From the numerical results, it can be concluded that tubes inserted at regular intervals on the hydrofoil significantly increase its performance at a higher angle of attack. [ABSTRACT FROM AUTHOR]

Design-by-Morphing (DbM) is a novel design methodology that creates a search space for topology optimization. Traditional design techniques often impose geometric constraints and, sometimes, the designer’s biases on the design space, which restricts the novelty of the designs and allows for only small local changes. On the contrary, we show in this paper that DbM does not impose such restrictions on the design space, thus allowing for a radical and expansive search space with only a few design parameters. We compare DbM with other methods in the case of design space generation for 2D airfoils and find that DbM can reconstruct the entire UIUC database with >99.5% accuracy. Furthermore, using a bi-objective genetic algorithm, we optimize the airfoil designs created by DbM to maximize both the lift-over-drag ratio, CLDmax, and stall angle tolerance, ∆α, which results in a Pareto-front of innovative airfoils that exhibit substantial improvements in both objectives.

An UAV (Unmanned Aerial Vehicle) is an aircraft without an onboard pilot that has several functions. Mohinder is one of the fixed-wing UAVs used for mapping and monitoring areas. Currently, the Mohinder UNNES is adopted from other UAVs by reduced-scale X-UAV Talon. There are differences between dimensions and cruising speed among Mohinder and X-UAV Talon (Mohinder adaptation). The purpose of this study is to select the suitable Mohinder’s airfoil using XFLR 5 simulation using multi-criteria decision particularly the AHP (Analytical Hierarchy Process). AHP can break down the choosing into a hierarchy, compare each factor's importance, and use math to figure out the best choice based on the preferences. The selection criteria are Max Camber, Thickness α stall, Max L/Dmax, CLmax, and CL0, so then the basic airfoil shapes are AH 79-100 B, S1223 RTL, FX 63-120, dan EPPLER 395. Mohinder airfoil will be selected based on aerodynamic performance at Reynold number 200.000. The simulation results showed the AH 79-100 B airfoil has higher L/Dmax and Cl at angle of attack (AOT) -10° to 20° compared to airfoil MH-32 (Mohinder current airfoil)

In the modern aviation environment, research on unmanned aerial vehicles is attractive in many aspects. Integrating efficient propellers into the unmanned aerial vehicle structure helps to enhance the performance factors such as endurance, range, distance to take-off and payload carrying capacity. This paper numerically investigates the configured propeller blades to enhance aerodynamic efficiency and performance parameters. The design parameters such as diameter, pitch, number of blades, and blade shape were configured with highly efficient propellers. The E62 airfoil opted to configure bi-blade, tri-blade, and modified nozzle-shaped ducted propellers and subjected to a computational fluid dynamic process for the varying rotational velocity. The thrust component, lift, drag and aerodynamic efficiency of the propeller blades were studied for the different operating speeds. The performance of E62 airfoil-based propeller was more efficient whereas the ducted blade profile generates the maximum thrust of 7.07N at the maximum angular velocity. [ABSTRACT FROM AUTHOR]

To enhance the aerodynamic performance of wind turbine blades, this study proposes the adoption of a bionic airfoil inspired by the aerodynamic shape of an eagle. Based on the blade element theory, a non-uniform extraction method of blade elements is employed for the optimization design of the considered wind turbine blades. Moreover, Computational Fluid Dynamics (CFD) is used to determine the aerodynamic performances of the eagle airfoil and a NACA2412 airfoil, thereby demonstrating the superior aerodynamic performance of the former. Finally, a mathematical model for optimizing the design of wind turbine blades is introduced and a comparative analysis is conducted with respect to the aerodynamic performances of blades designed using a uniform extraction approach. It is found that the blades designed using non-uniform extraction exhibit better aerodynamic performance. [ABSTRACT FROM AUTHOR]

The airfoil is the foundation of an aircraft, and its characteristics have a significant impact on those of the aircraft. Conventional airfoil design mainly focuses on improving aerodynamic performance, while flying wing airfoil designs should also consider layout stability and stealth performance. The design requirements for an airfoil vary with its position on the flying wing layout aircraft based on corresponding spanwise flow field characteristics. By analyzing the spanwise flow characteristics of the flying wing, partition design models for flying wing airfoils were established in this study, and a series of flying wing airfoil designs that consider aerodynamics and aerodynamic/stealth were implemented. Then, the designed airfoils were configured on a three-dimensional X-47B layout for testing and verification. The results showed that the aerodynamic design and the aerodynamic/stealth design exhibited significant improvements in terms for aerodynamic and longitudinal trimming characteristics. However, the cruise drag performance of the aerodynamic/stealth design was slightly worse than that of the aerodynamic design, although the longitudinal moment trimming characteristics were basically the same. The stealth characteristics of the aerodynamic/stealth design had significant advantages, indicating that there were weak contradictions between the aerodynamic, stealth, and trimming requirements in the design of the flying wing. [ABSTRACT FROM AUTHOR]

Ice can change the leading-edge profile of the airfoil and affect the overall aerodynamic performance of the airfoil. Studying the effects of simplified horn ice shapes on the flow field structures can provide a valuable reference for aircraft anti-icing/deicing design. Detailed experimental measurements of the flow field structures of the airfoil with different horn ice shapes were carried out in a low-speed direct wind tunnel using the particle image velocimetry technique. Three simplified ice shapes and the original ice shape were tested at different angles of attack. The results showed that, within the scope of the present study, there was a maximum 35.11% difference in the flow field parameters between the airfoil with simplified ice shapes and the airfoil with the original ice shape. Compared with the original ice shape case, the separation bubbles of the simplified ice shape cases were farther away from the leading edge and trailing edge of the airfoil. Among the three ice shape simplification methods, adding connecting lines between rectangular ice tips was found to have the optimum simplification effects in the flow structures and the airfoil performances. Using this simplification method, the maximum flow field differences at various angles of attack were within 14.88% in the selected two regions. [ABSTRACT FROM AUTHOR]

This study presents an extensive collection of data on the aerodynamic behavior at a low Reynolds number and geometric coefficients for 2900 airfoils obtained through the class shape transformation (CST) method. By employing a verified OpenFOAM-based CFD simulation framework, lift and drag coefficients were determined at a Reynolds number of 105. Considering the limited availability of data on low Reynolds number airfoils, this dataset is invaluable for a wide range of applications, including unmanned aerial vehicles (UAVs) and wind turbines. Additionally, the study offers a method for automating CFD simulations that could be applied to obtain aerodynamic coefficients at higher Reynolds numbers. The breadth of this dataset also supports the enhancement and creation of machine learning (ML) models, further advancing research into the aerodynamics of airfoils and lifting surfaces. Dataset:  https://github.com/kanakaero/Dataset-of-Aerodynamic-and-Geometric-Coefficients-of-Airfoils (accessed on 29 April 2024) Dataset License: The dataset and the framework are available under the MIT License [ABSTRACT FROM AUTHOR]

This research presents CFD analysis of the twodimensional subsonic flow over a GOE-387 airfoil at various thickness-to-chord ratios (t/C) and chord lengths, operating at a Reynolds number of 400,000. Lift Coefficient (CL), Drag Coefficient (CD), and CL/CD are investigated. The geometry of the airfoil is created using SolidWorks and Ansys Design Modeler. CFD analysis uses Ansys Fluent at various t/C from 5% to 25%, while the chord length varies from 100 to 200 cm. It was shown that variations in chord length have an effect in the form of increases and decreases in the value of the CL and a decrease in the CL/CD ratio, which is caused by the greater length value of the GOE-387 airfoil chord. In addition, variations in the thickness-to-chord ratio parameter also CLearly influence the aerodynamic characteristics of GOE-387 airfoil. The greater the t/C, the more significant the lift and drag coefficients increase while the CL/CD ratio decreases. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)