Symmetric Airfoil Research Articles

Improvement of Aerodynamic Performance of Bilaterally Symmetrical Airfoil by Co-Flow Jet and Adaptive Morphing Technology

For a special bilaterally symmetric airfoil (BSA), this paper designs an active flow control scheme based on the Co-Flow Jet (CFJ) and adaptive morphing technology, and establishes a numerical simulation method which is suitable for simulating aerodynamic characteristics. The accuracy and effectiveness of the numerical method has been verified through benchmark cases. This study investigates the effects of jet intensity, suction slot position and angle, and deflection angles of the leading and TE flap on the aerodynamic performance parameters and flow field structure of the bilaterally symmetric airfoil. The results show that the adaptive morphing technology can significantly improve the equivalent lift coefficient and equivalent lift-to-drag ratio of the bilaterally symmetric airfoil, without obviously increasing the CFJ power consumption coefficient. Selecting an appropriate CFJ intensity can achieve a relatively high equivalent lift-to-drag ratio with a low compressor power requirement. Moving the suction slot rearward can increase the lift coefficient, and placing it on the trailing edge (TE) flap can more efficiently delay flow separation, reduce power consumption, and increase the equivalent lift-to-drag ratio. The suction slot angle has little effect on the lift coefficient, but a larger suction slot angle can enhance the equivalent lift-to-drag ratio. Increasing the TE flap deflection angle enhances both the lift coefficient and drag coefficient, as well as the power consumption coefficient at high angles of attack. But it has little effect on the maximum equivalent lift-to-drag ratio. Increasing the leading edge flap deflection angle can improve the maximum equivalent lift-to-drag ratio while increasing the angle of attack corresponding to it. Overall, choosing a CFJ and adaptive morphing parameters by considering different factors can enhance the aerodynamic performance of the bilaterally symmetric airfoil.

Effects of Leading-edge Tubercles on the Aerodynamic Performance of Rectangular Blades for low-speed Wind Turbine Applications

The rapid depletion of conventional energy resources like fossil fuels has harmed the environment. Hence, there is an urgent need to seek alternative and sustainable energy sources. Wind energy is considered one of the efficient sources of energy that can be converted to a useful form of electrical energy. Though the field of wind engineering has developed in recent years there is still scope for improvement in the effective utilization of energy. The turbine blades' aerodynamics and the turbulent fluid flow characteristics largely determine the wind turbine's energy efficiency. Hence, in the present studies, we investigated the improvement of small wind turbine blade design by incorporating bioinspired tubercles into blades. One of the issues of small wind turbines is the low-capacity factor in power. The wind in such circumstances under buildings and other adjacent obstructions for small turbines is normally weak, unstable, and turbulent in wind speed and direction. Thus, the design of small turbines needs to be improved to capture low wind speeds and to respond quickly to turbulent wind resource areas. Biomimetics is a science that helps us adapt designs from nature to solve modern problems. The wing-like flipper of the humpback whale (Megaptera novaeangliae) has a morphology with potential for aerodynamic applications. The humpback whale flipper has several sinusoidal rounded bumps, called tubercles which modify the flow over the blade surface, creating vortices between the tubercles. Therefore, we conducted an XFOIL analysis of symmetrical NACA airfoils and we observed that NACA0012 could produce the best lift/drag ratio. The airfoil was then validated using Computational Fluid Dynamics (CFD) analysis in which the results were found comparable to that of the published data. Finally, CFD analysis was conducted for tubercles with a different pitch-to-amplitude ratio (p/A) and the tubercled airfoil with p/A of 6 provided the best result.

A numerical H Darrieus hydrokinetic turbine performance assessment with the application of openings in blade geometry

This study explores the impact of various geometric modifications, including leading-edge openings, trailing- edge openings, and circular openings, on the performance of the H Darrieus hydrokinetic turbine. These modifications involved the removal of material from a symmetrical NACA0018 airfoil along its surface. The leading edge and trailing edge openings extended from the lower to the upper surface of the blade, while the circular opening was applied exclusively to the upper surface. Using the commercial software ANSYS® V22.2, the turbine was designed, discretized, and analyzed through computational fluid dynamics employing the Realizable K-e turbulence model. The primary output variable measured was torque, from which the power coefficient for each design modification was derived, allowing for the calculation of efficiency in each scenario. Notably, the configuration featuring the upper circular opening achieved the highest efficiency at 51.88% at a Tip Speed Ratio (TSR) of 2.0, a significant improvement over the standard case which had an efficiency of 45.16%. In contrast, the leading-edge and trailing-edge openings resulted in reduced efficiencies of 44.54% and 31.19%, respectively. The enhanced power coefficient of the H Darrieus hydrokinetic turbine with circular openings is attributed to the increased pressure difference generated between the upper and lower surfaces of the blade, surpassing the performance of the standard design.

Aerodynamic characteristics and flow topology of tapered symmetrical airfoil equipped with Clark-Y shaped vortex generators

The aerodynamic characteristics and surface flow topology of tapered swept-back National Advisory Committee for Aeronautics 0020 airfoil equipped with Clark-Y shaped vortex generators (CsVGs) are researched. The force and surface oil flow visualization for the tapered swept-back wing having a swept angle of 25° and a taper ratio of 0.4 is performed at a Reynolds number (Re) of 1.2×105 via CsVGs at x/c = 0.2, 0.3, 0.4, and 0.5. The airfoil equipped with CsVGs at x/c = 0.2 [T2 at an angle of attack (AoA) of 13°] showed a 15.53% improvement in the maximum CL and a delaying stall by 2° comparison with the baseline [at AoA of 11°]. According to oil flow visualization, the T2 model enhanced the post stall characteristics via CsVGs by increasing the attached flow region from the root to the tip as compared to the baseline. While the straight laminar separation bubble (LSB) for the baseline was observed, a wavy LSB for T2 occurred due to the interaction of LSB with CsVGs located at 0.2c. Primary attach flow regions on the downstream of each CsVG, attached flow regions on the downstream of CsVG pairs, and interaction line due to the interaction of primary and attached flow region were identified via oil flow visualization.

Swot analysis of simulation methods and visualisation of airflow in subsonic wind tunnels

This paper contains concrete aspects aimed at strengthening research and innovation through specific activities in the field of aerospace research. This involves continuous research, finding new, modern, innovative solutions/processes that satisfy potential customers and through which we can keep competitive with existing aerospace research institutes on the market. In the case of improving the methods of simulation and visualisation of airflow around symmetrical airfoils we have carried out a SWOT analysis because it is a strategic method used to assess internal and external factors that can influence the success of an initiative or strategy.

Numerical study of dynamic stall effects on VR‐12 airfoil with pitch oscillation and accelerated inflow

AbstractThis study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch‐oscillating VR‐12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low‐Reynolds number correction, was employed for Re <105 during dynamic stall. The flow equations were solved in two‐dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil.

Optimization techniques for the design of crescent-shaped hard sails for wind-assisted ship propulsion

Wind-assisted ship propulsion is one of the most promising technologies to achieve net zero emission in ship operations by 2050 due to its reliance on a fully renewable energy source. Hard sails with crescent profiles have been shown to potentially provide a greater benefit than symmetric sails in recent studies. In order to justify their application, it is necessary to create and adopt a specific design that guarantees a reduction in the engine load over the whole operational range of encounter angles. The current study provides a systematic approach to obtain such a design based on two techniques, one aiming to maximum sail thrust, the other to minimize propeller power. Surrogate models based on validated CFD simulations are adopted for optimization, and the most efficient design is found as an average over all the possible encounter angles. It was shown that the thrust maximized approach increased the average thrust generated by sail up to 12.3%, and the propeller power minimized approach improved the effectiveness of the sails up to 22% in terms of percent power reduction. It was also confirmed that crescent-shaped airfoils generally outperform symmetric airfoils in the considered conditions.

Investigation of the decisive factor for the effectiveness of biomimetic protuberances during the stall process

This study investigates the influence of leading-edge protuberances (LEP) on the stall process of airfoils to identify the decisive factor in the effectiveness of LEPs. Owing to its clearly defined three-dimensional structure, an LEP introduces uncertainties into its effects on the stall angle of attack and the lift coefficient curve. This poses a challenge for several airfoils when universal stall control strategies are adopted. These problems were studied by classifying 12 symmetrical baseline airfoil types based on their blade thicknesses under the condition of Re = 180 000. These include thin airfoil stalls (TS), leading-edge stalls (LS), and a combination of leading-edge and trailing-edge stalls (CS). Two representative airfoils from each category were selected to study single-protuberance airfoils. The distribution of the suction surface momentum and evolution of the spanwise vortices revealed that the streamwise vortices induced by the LEP resulted in an attached flow. However, the impact of these flow patterns varies depending on the type of airfoil used. The TS and LS airfoils experienced an increase in the stall angle and maximum lift coefficient, resulting in an overall improvement in the airfoil performance. The CS airfoils are the most heavily influenced, experiencing a decrease in the maximum lift coefficient and exhibiting phenomena such as a one-sided stall and step-by-step stall. Finally, this paper proposes for the first time that the main factor influencing the different effects of protuberances is the stall type of the airfoil. This new knowledge can serve as a valuable reference for the implementation of protuberances in practical mechanical applications.

Optimizing Obscurity: Advancing Stealth Capabilities and Performance of BWB Fighter with Symmetric Supercritical Airfoils

Optimizing Obscurity: Advancing Stealth Capabilities and Performance of BWB Fighter with Symmetric Supercritical Airfoils

Parametric investigation of aerodynamic performance degradation due to icing on a symmetrical airfoil

Ice accretion on lifting surfaces induces an aerodynamic penalty in lift and drag on an aircraft. This performance degradation depends on the geometric features, type, and surface characteristics of the accreted ice on the airfoil. In the present work, we propose a set of two-parameter, low-order models to represent some of the typical ice topologies: glaze, rime, and horn. The parametric space is swept for all types of ice to isolate the aerodynamic changes causing performance degradation on a canonical symmetrical airfoil, which is the representative airfoil used by the National Research Council of Canada's platform for ice accretion and coatings tests with ultrasonic readings platform for in-flight icing tests. The three ice topologies show a self-similar trend between the stall angle of attack and the ice thickness, with the horn-type of ice imparting the greatest drag and lift penalty due to strong boundary layer separation. The relative effect of ice roughness plays a secondary role in performance degradation, and in some cases, the roughness causes a thicker and more resilient boundary layer, which can, under very specific icing conditions, enhance the aerodynamic performance.

Comparative analysis of compressible inviscid flow over symmetric and supercritical airfoil

Studying compressible inviscid flow over symmetric and supercritical airfoils is important because it is useful to understand and maximize aerodynamic performance in a range of industrial contexts. This study addresses the analysis of symmetric and supercritical airfoils for compressible inviscid flow for both time-dependent and stationary scenarios. The primary goal of these simulations’ is to look at how different velocity variations affected certain airfoil parameters. Air is utilized as the material above airfoils. The best fit for these simulations is the Spalart-Allmaras Turbulence model, which shows good agreement over a wider velocity range with published experimental data from other studies. The COMSOL Multiphysics software is used for all the analysis, for angle of attack 0°, temperature 288K, pressure 1bar and the airfoils that are constructed by importing airfoil data file in COMSOL in the form of excel file. On the comparison of compressible inviscid flow, the supercritical airfoil has better results on the basis of velocity magnitude, pressure, vorticity magnitude, shear rate and rotation rate. The results are converging faster in supercritical airfoil than symmetric airfoil. At a zero-degree angle of attack, velocity increases more on the suction side while decreases on the pressure side (bottom). The final solution error for supercritical airfoil is 1.6E-05, while final residual error for “velocity u pressure p” is 1.2E-05. For symmetric airfoil, final solution error is 0.15, although final residual error is 2.6. Based on the error plot, it decreases rapidly in case of supercritical with a range from 100 to 10-4. Additionally, the wall resolution is constructed for both cases i.e., symmetric airfoil and supercritical airfoil. The main result is that ,with the passage of time, the flow is becoming to stationary state. In the end, model validation via comparison with experimental data highlights the validity and applicability of the results.

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.

Influence of Surface Roughness on Symmetric Airfoil Flow Properties and Reynolds Number

Collaborative Aircraft Design Optimization: Investigating Roughness Management of Wings to Reduce Drag and Improve Performance This study investigates the potential of roughness control of aircraft wings based on joint design optimization. By adding roughness points to specific wings, our goal is to reduce drag and improve the overall performance of the aircraft. A multi-modal design optimization (MDO) framework combining aerodynamics, modelling, and performance analysis was used in this study. We measure the effect of tissue on the boundary layer, the progression of laminar flow, and the potential for weight savings due to reduced friction. This study investigates how roughness control interacts with other design factors such as flow components or blade materials to achieve optimal performance. The ultimate goal is to create a collaborative design that uses tissue management to contribute to next-generation fuel efficiency and high performance. Keywords – CFD, Surface Roughness, Wind Tunnel, Aerodynamic Efficiency.

Aerodynamic performance and starting torque enhancement of small-scale Darrieus type straight-bladed vertical axis wind turbines with J-shaped airfoil

Wind energy is one of the most eminent renewable sources for the generation of power. The increasing enthusiasm toward the advancement of small-scale Darrieus type straight-bladed vertical axis wind turbines (SB-VAWTs) can offer a potential remedy for addressing power shortage and the unpredictability of climate conditions. These particular wind turbines provide distinct advantages over their counterparts due to their linear blade design and uncomplicated structure. However, enhancements are required in their aerodynamic efficiency and self-initiation capabilities. These challenges stem from using traditional straight blade configurations and symmetrical airfoils. By substituting these conventional elements with J-shaped straight blades and along with cambered airfoils, these issues can be effectively overcome. The current study aims to investigate the effect of J-shaped straight blades with a series of cambered airfoils to improve the aerodynamic performance and starting torque of small-scale Darrieus type SB-VAWTs. Therefore, experimental and numerical studies are conducted to analyze the J-shaped airfoil impact with various opening ratios systematically. The J-shaped blade profile is designed by eliminating some portion toward the trailing edge of a conventional airfoil. This analysis demonstrated that the J-shaped blade incorporating a cambered NACA 4418 airfoil outperforms its alternative cambered airfoil designs. The performance of SB-VAWT improves by about 25% by the J-shape of the cambered NACA 4418 airfoil with a 70% opening ratio. Moreover, the use of J-shaped airfoils enhances the self-starting torque of SB-VAWT compared to conventional airfoils.

Research on the Overall Influence of Magnus Cylinders on Airfoil Structures and Structural Optimization

With the coupling effect of Magnus cylinder and symmetric airfoil as the research object, the numerical analysis method is used to study the influence of Magnus cylinder layout position and protruding height ratio on the aerodynamic characteristics of the airfoil. Based on the aerodynamic law of Magnus airfoil and Optistruct deformer optimisation method, the optimisation model of Magnus airfoil structure is proposed. Results reveal that the placement of the Magnus cylinder near the leading edge of the upper surface and the trailing edge of the lower surface significantly impacts the aerodynamic characteristics of the Magnus airfoil. Moreover, as the protruding height ratio increases, the aerodynamic performance of the airfoil experiences an initial enhancement followed by a reduction. Under the conditions of an 8° angle of attack and a Reynolds number of 9.5×105, the optimized aerodynamic performance of the Magnus airfoil demonstrates a remarkable increase of 17.5% compared to the baseline airfoil, accompanied by a significant reduction of 28.1% in stress concentration.

Effects of Simulated Surface Roughness on Flow Characteristics in Symmetrical Airfoil

Managing wing roughness to reduce drag and support by contributing towards the stabilization. This work is inspired by the phenomenon of sand paper to investigate the concept of roughness control on an aircraft wing. Similar to the quality of the sand paper based on the grate of the sand paper, the concept of providing rough detail on wings can reduce skin drag and increase aerodynamic efficiency. Using an integrated plane design optimization, we use wind tunnel measurements to investigate the effects of boundary fabric, response behavior and overall attenuations. The study investigated how roughness control interacts with other design elements such as wing shape and material selection to achieve the best aerodynamic performance. This research is helping develop next-generation aircraft that use roughness-inspired designs to achieve significant fuel savings and environmental benefits through effective coordination. Keywords – CFD, Surface Roughness , Aerodynamic Efficiency.

Convolutional Neural Networks-Based For Predicting Aerodynamic Coefficient Of Airfoils At Ultra-Low Reynolds Number

Many applications, including airplane design, wind turbines, and heat transmission, use symmetric or asymmetric airfoils. Engineers employ these airfoil shapes to optimize performance and efficiency. Each airfoil has a unique set of aerodynamic coefficients that must be calculated to maximize the airfoil design. Engineers utilize numerous ways to calculate coefficients, such as lift and drag. One of the methods is the prediction method, which effectively reduces time and cost. This study's training dataset is obtained from particle-based numerical computation using the Lattice Boltzmann Method (LBM). Then, Convolutional Neural Networks (CNN) are used as a prediction method to get the aerodynamic coefficients of airfoils for lift and drag based on two different Reynolds numbers. In CNN, airfoil geometry representation is essential. The Signed Distance Function (SDF) was used to convert airfoil geometry into RGB pictures. On the other hand, the SDF method cannot explain different flow conditions; in this case, it is represented by the Reynolds number (Re). Therefore, we propose a Text-based Watermarking Method (TWM) to differentiate between Re = 500 and Re = 1000. Each airfoil representation was trained and tested to generate each prediction model using a modified LeNet-5. The computation results show that using CNN with TWM on SDF to define the Reynolds numbers could predict the lift and drag coefficients with varying angles of attack. Future research can focus on generalizations to different aerodynamic aspects and practical applications in complex scenarios.

Comparative Assessment on Unsteady Aerodynamics of Thin and Thick Airfoils Subjected to Pitching Motion

This article presents the comparison between the unsteady flow characteristics of thick (t/c ≥ 6%) and thin (t/c ≤ 6%) airfoils performing pitching motion at Reynolds number Re = 3.6 × 10 5 . For the analysis, the considered airfoils are NACA 0012 as thick and symmetric airfoil and GOE 417A as thin and highly cambered airfoil. The analysis in this study is restricted to only two airfoils because from the preliminary investigations, similar aerodynamic characteristics with slight variation in their flow field development under same conditions were observed. The influence of reduced frequency, pitching amplitude and mean angle of attack on the airfoil’s aerodynamic performance in terms of instantaneous force coefficients is thoroughly investigated. Further, the flow surrounding the airfoils is also investigated. It is noticed that the aforementioned parameters substantially affect the instantaneous force coefficients (both qualitatively and quantitatively). Under certain conditions, the formation of reverse Karman vortex street was observed indicating airfoil’s thrust force generation. It must be noted that the conditions where the thrust force generation occurs for thick and symmetric airfoils like NACA 0012 are quite different from that of thin and cambered airfoils like GOE 417A. Additionally, a drastic change in the flow field around the airfoils is observed under similar conditions. For NACA 0012 airfoil, the formation and convection of the Leading Edge Vortex (LEV) under certain conditions has detrimental effects on its aerodynamic characteristics as it encourages early flow separation. However, the same cannot be true for thin and highly cambered airfoils like GOE 417A. Under the similar conditions with negligible variation, the LEV contributes toward providing extra suction over the GOE 417A airfoil’s suction side. This significantly improves airfoil’s aerodynamic characteristics.

Investigating the Impact of Plain Flap as Lift Enhancement on Symmetrical Airfoils

Investigating the Impact of Plain Flap as Lift Enhancement on Symmetrical Airfoils

Implementation of a PAFV turbulence model for airfoil flow simulation on OpenFOAM

To further develop a more effective turbulence model and to improve the calculation accuracy of the flow around airfoil, a new PAFV turbulence model has here been constructed by using a deformation rate tensor and the grouping of an average fluctuation velocity. To evaluate the applicability of the PAFV turbulence model, the numerical calculations of flow around the airfoil have here been implemented, which was based on the OpenFOAM calculation platform. On the basis of grid independence research, the model was used to calculate the low-speed flow-around problem for the plano-convex airfoil NACA4412 and the symmetric airfoil NACA0012. It was also compared with the S-A (Spalart-Allmaras) and SST (Shear Stress Transport) k-ω turbulence models. Firstly, the maximum lift angle-of-attack case of the NACA4412 airfoil was calculated. Thereafter, numerical calculations were performed for the flow around the airfoil in the multi-angle-of-attack case of the NACA0012 airfoil. The results showed that the NACA4412 airfoil had an obviously separated vortex at the trailing edge of the airfoil at the maximum lift angle of attack. Also, there was a certain velocity loss downstream of the trailing edge, which was calculated by all three models. However, the results of the PAFV turbulence model were found to be better than those of the S-A and SST turbulence models. The three turbulence models showed comparable accuracies for the calculations of the surface pressure coefficients of the NACA0012 airfoil. However, the S-A and SST k-ω turbulence models were slightly better for the calculations of the mean velocity profiles of the NACA0012 airfoil. Also, the PAFV turbulence model was more accurate for the calculations of the lift and drag coefficients. In conclusion, the PAFV model can make effective predictions of the airfoil low-speed flow around the problem at hand, which in turn preliminarily verifies the applicability of this turbulence model for the low-speed flow around the airfoil problems.