Leading-edge Modifications Research Articles

Hydrodynamic performance of pitching foils with two leading-edge protuberances

Inspired by the tubercles on humpback whales, the ‘tubercle-effect’ first identified by (Fish and Battle, 1995; Fish and Lauder, 2006) had been studied extensively to understand their influence on overall efficiency for airfoils and wings. Pitching and/or heaving motion of foils produces net thrust inspired from fin-based locomotion of aquatic animals, and is often being proposed as a greener means of propulsion having reduced acoustic signature. With this aim in mind, the present work investigates the effect of using tubercles on pitching motion of foils. The hydrodynamic characteristics of finite aspect ratio pitching foils having leading-edge modifications in the form of two protuberances are investigated using experiments. The thrust and efficiency with and without protuberances are investigated for pure pitching motions at reduced frequencies (1.8 – 3.2) and pitching amplitudes (7.5°- 20°) for Reynolds number 2 × 104. The experimental results are compared with inviscid linear theory calculations which over-predict the mean thrust, while the amplitude of the lift force and its variation with reduced frequency is similar. The performance improvements in terms of thrust and efficiency for the modified design are restricted to ≥15° pitching amplitudes at higher reduced frequencies. The wake vorticity patterns obtained using Computational Fluid Dynamics investigations show the influence of the leading-edge vortex, which gets modified when the protuberances are used. The transition from 2S wake to 2P wake with the increase in the amplitude of oscillation is captured. The reversal of von Kármán Vortex Street with the pitching frequency and thus the transition from drag to thrust generation is observed for both the baseline and modified foil designs. The results indicate that protuberances over the leading-edge of hydrofoils can influence the hydrodynamics during pitching motion and can be effectively employed for performance tailoring based on the geometry and motion characteristics. The simplified setup used here is also meant to serve as a basis towards future research including verification and validation work for numerical solvers.

Influence of a novel leading-edge winglet on the aerodynamic characteristics of a highly loaded turbine

In order to decrease the flow loss of the region close to the endwall, a novel leading-edge modification strategy is proposed in this paper. Specifically, the winglet is installed at the leading edge of the first-stage blade of the highly loaded PW-E3 (Energy Efficient Engine designed by Pratt & Whitney Aircraft Group) turbine. The numerical methods used in this study are validated with the experimental data of the original blade profile of PW-E3. The SST (Shear Stress Transport model) γ-θ turbulence model is employed to calculate the flow field. The schemes of the forward bending winglet and reverse bending winglet are compared with the base case to prove the superiority of this modification strategy. The numerical results indicate a significant increase in stage efficiency by reducing the total pressure loss coefficient. Reverse bending winglets perform better than forward bending ones in terms of efficiency promotion. The effects of the normalized winglet height and bending angle are further explored. For reverse bending winglets, increasing the normalized winglet height and bending angle leads to improved flow control. Conversely, for forward bending winglets, reducing the normalized winglet height and bending angle is more favorable for loss reduction.

Investigations of specific modifications in pump as turbine towards performance improvement

ABSTRACT Centrifugal pumps as turbines offer a proven green energy solution for sustainable development, potentially replacing costly custom turbines in micro-hydro power plants and providing cost savings. But the efficiency of the pump as a turbine is lower than that of the dedicatedly designed pump. In this study, new simple modifications are proposed and evaluated on a developed state-of-the-art PAT test rig with impeller of specific speed 43.7 (m-m3/s). Being simple modifications, cost benefits will remain intact without requiring specially designed turbines and trained manpower. New simple modifications in PAT, like balance holes filling, packing seal optimization with appropriate size, leading edge of impeller blade tips modification making it single curve, and inner shroud widening for increasing the width at the inlet of the impeller, were proposed and performed to investigate the influence of the modifications on PAT performance. The experimental study finds that optimal packing seal size and impeller leading edge modifications notably boost PAT efficiency by 3–3.5%, making it worthwhile to implement for resource conservation and performance enhancement. On the other side, inner shroud widening noticed a 1.2% reduction in efficiency, adversely affecting the performance of PAT. Additionally, balance hole filling is neutral and does not have any effect.

Leading Edge Modification of NACA 0015 and NACA 4415 Inspired by Beluga Whale

Leading Edge Modification of NACA 0015 and NACA 4415 Inspired by Beluga Whale

Investigation on the Performance of Micro Wind Turbine Rotor Using Whale-Inspired Blade Based on Low Wind Regime

The potential of wind energy in a country varies depending on the region. For example, in Northern regions of Nigeria, cities like Minna, Sokoto, Kano and Jos are the most potential locations and experience not more than 5.24 m/s mean wind speed with Jos having the highest average wind speed. In most cases internationally wind turbines are design to operate at the rated wind speed much greater than mean wind speeds in Nigeria (in most cases above 8 m/s). Installation of these wind turbines in a similar location to Nigeria (in terms of wind speed condition) will significantly decrease their performance. Therefore, it become necessary to design and produce wind turbines that will function efficiently in low wind speed locations. One of the technologies to improve wind turbine rotor blade effectiveness in low wind regime is to boost the operating angle of the wind turbine, and hence the prospect for the improvement of wind turbine performance. An innovative way recognized previously by some researchers for increasing the working angle of the blade at low wind speed for improved performance is modification of wind turbine blade leading edge. This research studied three-bladed wind turbine rotor with modified blades leading edges (by incorporating sinusoidal bumps) at low wind speeds using CFD method. Two CAD models of wind turbine blades based on 0.8m three-bladed wind turbine rotor were modelled and simulated. One blade model is having straight leading edge (N-Blade) and the other having bumpy leading edge (M-Blade). Both models have NASA LS (1)-0413 cross-section profile. Simulations were run using ANSYS 20 from a velocity of 2 m/s to 10 m/s at the interval of 2m/s considering TSR of 6 and 8. At a TSR of 6, the coefficients of performance (Cp) values are not equal, with the straight blade having better performance than the bumpy blade at all velocities tested; the Cp values of blade with straight leading edge are 0.180, 0.267, 0.300, 0.313, 0.322 at respective velocities of 2, 4, 6, 8, and 10m/s, while Cp values of blade with bumpy leading edge at the same velocities are 0.165, 0.250, 0.281, 0.294, and 0.303 respectively. At a TSR of 8, the CP values closely match for both straight and bumpy blade at all velocities tested for. Simulations were further run at constant angular velocity of 120 rad/s for a TSR of 2, 4, and 10, where the peak performance occurs is around TSR of 6 and 8. For instance, the Cp values of M-Blade are 0.022, 0.173, 0.294, 0.313, and 0.116 respectively at the TSR of 2, 4, 6, 8, and 10. At TSR of 2, 4, 8 and 10, the performance of both airfoils closely matches except at a TSR of 6 where the N-Blade Cp value is 0.313 and is better than that of M-Blade Cp value (0.294). It shows that the blade leading edge modification could not have advantage at all flow conditions and size of the HAWT blades; it shows no advantage on the performance of the rotor blade tested in this research at the velocities at which the simulation was conducted.

Experimental investigation on cavitation and induced noise of two-dimensional hydrofoils with leading-edge protuberances

The applicability of leading-edge protuberances as a passive flow control approach inspired by humpback whale flippers has attracted significant research attention in aquatic and aeronautic systems because of their influence on critical hydrodynamic and aerodynamic aspects. An experimental investigation is conducted in a cavitation tunnel under various flow conditions to determine the effectiveness of leading-edge protuberances in controlling the detrimental effects of cavitation and suppressing flow-induced noise. The experiments are carried out on four National Advisory Committee for Aeronautics airfoil 0012 hydrofoils at 7° attack angles and free stream velocities up to 10 m/s. One of the four hydrofoils is considered the baseline, while the other models have wavy leading-edge modifications with different sinusoidal protuberances. These geometry modifications are defined by the amplitudes (A) (2% and 4% of the mean chord length) and wavelengths (λ) (12.5% and 25% of the mean chord length) of the sinusoidal protuberances. Investigations of flow over hydrofoils from top and side views at various Reynolds numbers exhibit that cavitation first appears in the modified hydrofoils' troughs and is restricted to just behind the protuberance troughs for the entire cavitating flow range. These results contrast the baseline geometry, where cavitation inception occurs at the flat leading edge, and the sheet cavity expands spanwise with extensive cloud shedding. Image processing under certain conditions reveals that the protuberances reduce cavitation by 25%–60%. The analysis of the sound pressure level demonstrates that the leading-edge protuberances effectively decrease flow-induced noise at higher flow velocities when cavitation is the dominant noise source. Finally, the direct comparison of cavitating flow characteristics, quantitative cavitation measurements, and noise production analysis between the baseline and modified hydrofoils, and their comparison among the modified geometries, provides a significant reference for future modeling of potential applications employing this passive flow control technique.

On the acoustic emission characteristics of airfoils with different trailing edge configurations

The present study experimentally and numerically investigates the flow past flat plates and NACA0012 airfoils with the different trailing edge (i.e., blunt, sharp, and rounded) and both end-rounded configurations on the far-field acoustic emissions and complex flow phenomena to determine the best edge geometry for low noise. The studies are conducted for various jet speeds of 20, 30, and 40 m/s (chordwise Reynolds numbers of 1.812 × 105, 2.72 ×105, and 3.62 ×105). It is observed that all the edge-modified flat plates show the highest directivity at an emission angle of 60° for all jet velocities studied. The comparison of power directivities between realistic and flat plate airfoils reveals that the realistic airfoils radiate lower acoustic emissions as compared to flat plate airfoils, albeit they show a common feature of downstream directivity. In general, the far-field acoustic emissions of both end-rounded plates are observed to be lower as compared to blunt, sharp, and rounded trailing edge geometries. The leading edge modification is also observed to reduce airfoil self-noise. The likely reason for the lower far-field acoustic emissions provided by both end-rounded trailing edged foils is due to the modification in the boundary layer characteristics owing to the presence of smooth flow around the rounded leading edge as well as reduced vortex strength as compared to the other foil geometries. Thus, the present study demonstrates that passive modifications of leading edge profiles are essential along with trailing edge for achieving lower acoustic emissions and higher noise reductions.

Vortex dynamics impact on the wake flow of a marine rudder with leading-edge tubercles

The impact of two tubercle leading-edge (TLE) modifications on the turbulent wake of a reference marine rudder at Reynolds number 2.26 × 106 was analysed numerically using Detached Eddy Simulations (DES). This paper studies the counter-rotating vortex pair formation around the TLE and their impact on the wake structures behind the rudder to find out if the vortex interaction can accelerate the tip vortex dissipation. According to the results, the tubercles enhanced lift for angles of attack (AOA) 10º and above, but at the cost of a drag penalty which reduced the rudders’ lift-to-drag ratio. The formation of the distinctive stream-wise counter-rotating vortex pairs occurred behind the tubercles, which then interacted with the dominant tip vortex. Due to the inherent spanwise flow component of finite-span lifting surfaces the counter-rotating vortex pairs were generated at unequal strength and soon merged into singular vortices co-rotating with the tip vortex. The vortices facilitated flow compartmentalisation over the rudder suction side which broke up the trailing-edge vortex sheet and confined the spanwise flow separation over the rudder surface as AOA increased. The tubercles confined flow separation closer to the rudder tip which reduced the lift generation in the tip area and minimised the initial tip vortex strength. Large elements of stream-wise counter-rotating vorticity formed around the localised stall cells of the TLE rudders that interacted with the tip vortex downstream, introducing elliptical instabilities further weakening the tip vortex and changing its trajectory.

Hydrofoil geometry and leading-edge modifications: Influence of section profile, aspect ratio, and sweep

Modifications mimicking the leading-edge protuberances on the pectoral fin of humpback whales have been widely adopted to the designs of foils and control surfaces to delay stall and provide post-stall superior lifting characteristics. However, the efficacy of these modifications in flow control and lift augmentation depends on the wing geometry. The present work investigates the lift, drag, and flow characteristics of finite-span hydrofoils with different section profiles-both symmetric and cambered (NACA 0012, NACA 0018, NACA 634-021, NACA 2412, and NACA 4415) having twin-protuberances over their leading-edge at a Reynolds number of 2 × 105. The influence of aspect ratio (1, 2, and 3) and leading-edge sweep angle (0 deg, 15 deg, and 26.1 deg) on the hydrodynamic performance of modified foils is also investigated. The characteristic feature of twin-protuberance foil designs is the restriction of flow separation between the chordwise vortices shed from the two protuberances in certain post-stall regimes. The use of leading-edge modifications is observed to be more conducive for lift enhancement in thin foil sections, especially NACA 0012, having a smaller stall angle. Considering the other parameters, leading-edge protuberances are observed to be advantageous for hydrofoils with aspect ratios 2 and 3 at post-stall angles of attack, and for 0 deg and 15 deg sweep angles for post-stall lift enhancement. The influence of Reynolds number on the performance modifications is also investigated.

The Influence of Leading-Edge Tubercles on the Wake Flow Dynamics of a Marine Rudder

The impact of two tubercle leading-edge (TLE) modifications on the turbulent wake of a representative marine rudder at Reynolds number 2.26×106 was analysed numerically using Detached-Eddy Simulations. TLE have been shown to alter the flow profile over aero/hydrofoils through the generation of streamwise counter-rotating vortex pairs behind the tubercles, which can enhance the lifting performance. This paper studies the formation of these vortex pairs and their impact on the wake structures behind the rudder to find out if vortex interaction can reduce the tip vortex. The tubercles enhanced lift for angles of attack (AOA) 10o and above, but at the cost of a large drag penalty that reduced the rudders' lift-to-drag ratio. The formation of the distinctive streamwise counter-rotating vortex pairs behind the tubercles was shown. Due to the inherent spanwise flow component of finite-span lifting surfaces the vortices were generated at unequal strength and only positive vortices were maintained in the wake. The vortices facilitated flow compartmentalisation over the rudder suction side which broke up the trailing-edge vortex sheet and confined the spanwise flow separation over the rudder surface as AOA increased. The tubercles confined flow separation closer to the rudder tip which caused a tip-offloading effect that minimised the initial tip vortex strength. Large elements of streamwise counter-rotating vorticity formed around the localised stall cells of the TLE rudders that interacted with the tip vortex downstream, introducing elliptical instabilities further weakening the tip vortex and changing its trajectory.

Initial development of the hybrid semielliptical-dolphin airfoil

Iosif Taposu has formulated a mathematical model and generated a family of airfoils whose geometry resembles the dolphin shape. These airfoils are characterized by a sharp leading edge and experiments have proven that they can achieve better aerodynamic characteristics at very high angles of attack than certain classical airfoils, with the nose geometry inclined downwards. On the other hand, they have not been applied to any commercial general aviation aircraft. The authors of this paper have been motivated to compare the aerodynamic characteristics of widely used NACA 2415 airfoil with Taposu?s Dolphin that would have the same principal geometric characteristics. A CFD calculation model has been established and applied on NACA 2415. The results were compared with NACA experiments and very good agreements have been achieved in the major domains of lift and polar curves. The same CFD model has been applied on the counterpart Dolphin 2415. Results have shown that the Dolphin has a slightly higher lift/drag ratio in the lift coefficient domain 0.1-0.35 than NACA. On the other hand, at higher and lower lift coefficients, its aerodynamic characteristics were drastically below those of the NACA section, due to the unfavorable influence of the Dolphin?s sharp nose. A series of the Dolphin?s leading edge modifications has been investigated, gradually improving its aerodynamics. Finally, version M4, consisting of about 70% of Dolphin?s original rear domain and 30% of the new nose shape, managed to exceed the NACA?s characteristics, thus paving the way to investigate the Dolphin hybrids that could be suitable for the general aviation industry.

A numerical investigation into the influence of bio-inspired leading-edge tubercles on the hydrodynamic performance of a benchmark ducted propeller

Marine ducted thrusters are widely used to provide propulsive thrust for a range of marine vessels due to their high thrust capability in heavy loaded conditions. This paper presents a novel and optimised bio-inspired marine ducted thruster, where leading-edge tubercles are applied to the duct of a ducted propulsor to explore the impact on hydrodynamic performance. Nine different geometrical configurations of tubercle were investigated with varying amplitude and wavelength within the optimisation study. The hydrodynamic performance of the marine ducted thruster is evaluated using a commercially available computational fluid dynamics (CFD) code, STAR-CCM+, with an incompressible implicit unsteady Reynolds-Averaged Navier Stokes (RANS) solver combined with the Body Force Propeller (BFP) method for the duct optimisation study. Then, the selected optimal duct was chosen for further analysis using the propeller resolved Rigid Body Motion (RBM) method, more commonly known as the sliding mesh technique. Through the numerical optimisation study, the leading-edge modification is predicted to have the capability to enhance the duct thrust in the heavy-loaded conditions, although this is dependent on the wavelength and amplitude of the tubercle. Furthermore, during the investigation the traditional tubercle behaviour was observed, namely the high-low pressure patterns and streamwise counter-rotating vortices. Interestingly, flow separation was observed to be compartmentalised on the outer side of the duct cross-section in conditions where flow separation occurred such as at the maximum efficiency operating point.

Flow separation control using the cetacean species nose design

Most of the flow separation control devices used in the aircraft wing are effective at high angles of attack, and adversely affect the performance of the wing at low angles of attack. In flight mission, the cruise phase takes major portion than the take-off and landing. Therefore, the flow separation control devices installed on wing may reduce the performance of the aircraft in total flight mission. A bio-inspired passive flow control method is used by introducing leading edge modification. The leading edge modification inspired by the cetacean species (Porpoise) has been analyzed on NACA2412 and NACA66215 airfoils at different subsonic speed using 2D analysis. The effect of the spanwise location and extent of these leading edge modifications is analyzed using a three-dimensional numerical investigation. The porpoise nose design (shorter length and medium depth i.e. depth — 2.25 % of chord, nose length — 0.75 % chord, and nose diameter — 2 % chord) delay the flow separation and improves the aerodynamic efficiency up to the critical Mach number. After critical Mach number, the shock wave formation affects the porpoise nose performance and shows similar flow behavior as base airfoil. A finite wing with a porpoise nose design of full spanwise length showed the better aerodynamic efficiency than base wing model. This rigid design improves aerodynamic performance of a wing without major structural modification.

Effects of Leading-Edge Modification in Damaged Rotor Blades on Aerodynamic Characteristics of High-Pressure Gas Turbine

The flow and heat-transfer attributes of gas turbines significantly affect the output power and overall efficiency of combined-cycle power plants. However, the high-temperature and high-pressure environment can damage the turbine blade surface, potentially resulting in failure of the power plant. Because of the elevated cost of replacing turbine blades, damaged blades are usually repaired through modification of their profile around the damage location. This study compared the effects of modifying various damage locations along the leading edge of a rotor blade on the performance of the gas turbine. We simulated five rotor blades—an undamaged blade (reference) and blades damaged on the pressure and suction sides at the top and middle. The Reynolds-averaged Navier–Stokes equation was used to investigate the compressible flow in a GE-E3 gas turbine. The results showed that the temperatures of the blade and vane surfaces with damages at the middle increased by about 0.8% and 1.2%, respectively. This causes a sudden increase in the heat transfer and thermal stress on the blade and vane surfaces, especially around the damage location. Compared with the reference case, modifications to the top-damaged blades produced a slight increase in efficiency about 2.6%, while those to the middle-damaged blades reduced the efficiency by approximately 2.2%.

Study of Aerodynamic Performance and Power Output for Residential-Scale Wind Turbines

Abstract This study presents the rotor blade airfoil analysis of residential-scale wind turbines. On this track, four new airfoils (GOE 447, GOE 446, NACA 6412, and NACA 64(3)-618) characterized by their high lift-to-drag ratios (161.3, 148.7, 142.7, and 136.3, respectively). These new airfoils are used to generate an entire 7 m long blades for three-bladed rotor horizontal axis wind turbine models tested numerically at low, medium, and rated wind speeds of 7.5, 10, and 12.5 m/s, respectively, with a design tip speed ratio of 7. The criterion to judge each model’s performance is power output. Thus, the blades of the model that produce the highest power are selected to undergo a tip modification (winglet) and leading-edge modification (tubercles), seeking power improvement. It is found that the GOE 447 airfoil outperformed the other three airfoils at all tested wind speeds. Thus, it is opted for adding winglets and tubercles. At 12.5 m/s, winglet design produced 5% more power, while tubercles produced 5.5% more power than the GOE 447 baseline design. Furthermore, the computational domain is divided into two regions: rotating (the disc that encloses the rotor) and stationary (the rest of the flow domain). Meanwhile, the numerical model is validated against the experimental velocity measurements. Since Reynolds-averaged Navier–Stokes with k–ω shear stress transport turbulence model can capture the laminar-to-turbulent boundary layer transition, it is used in the 18 simulations of the current work. However, large eddy simulation (LES) can deal successfully with the various scale eddies resulting from the rotor blades and its interactions with the surrounding flow. Thus, the LES was used in the six simulations done at the rated wind speed. LES power output calculation is 7.9% to 11.9% higher than the RANS power output calculation.

Flow control of non-slender delta wings by leading-edge modifications

Different concepts for controlling a non-slender delta wing are considered and compared with each other. The concepts are based on geometrical modifications of the leading edges. The strategy aims at producing an asymmetric distribution of lift due to vortices on the left and right wing half and thus, for example, rolling moments to be used in controlling the model. The effectiveness of different approaches is determined in low-speed wind tunnel tests both by measuring forces and moments acting on the model and by investigating the flow field around the model by particle image velocimetry and oil-flow visualization of skin friction lines. Two approaches are pursued. One is based on static and dynamic actuators acting at the left leading-edge. The other uses different combinations of leading edge shapes on the two halves of the model. Finally, the effect of asymmetric boundary layer tripping is briefly considered.

Experimental Investigation of the Sound Emission of Skewed Axial Fans with Leading-Edge Serrations

Axial fans represent a major source of noise in technical systems. Based on investigations on airfoils, a promising measure for reducing the sound emission of such systems with axial fans is the application of leading-edge serrations to the fan blade. Hence in this study, the joint impact of fan-blade skew—as a commonly used noise-reduction approach—and leading-edge serrations on the sound emission of low-speed axial fans was investigated. Forward-, backward-, and unskewed fans with five different leading-edge modifications were used. For each fan, a reference configuration with straight leading edges and four configurations with sinusoidal leading-edge serrations (with two different amplitude values and two different wavelength values) were examined. The results show that, among the reference fans with unmodified leading edges, the forward-skewed fan had the lowest sound emission. The serrations applied to the unskewed fan lead to an increase in the efficiency and a decrease in the sound emission. When applied in combination with fan-blade skew, the serrated fans showed an even lower sound emission and a higher efficiency—even the forward-skewed fan, which already has a low sound emission without any leading-edge modifications. The highest sound reduction was achieved by applying the serrations with the smallest wavelength and the highest amplitude. The findings prove that even for low-noise fans with forward-skewed fan blades, a further sound reduction is possible with the use of leading-edge serrations.

Enhancing aerodynamic performance of NACA 4412 aircraft wing using leading edge modification

This work deals with designing the aircraft wing and simulating the flow behavior on it to determine the aerodynamically efficient wing design. A NACA 4412 airfoil is used to design the base wing model. A wing with a rectangular planform and the one with curved leading edge planform was designed such that their surface areas are the same. Then, a comprehensive flow analysis is carried out at various velocities and angle of attacks using computational fluid dynamics (CFD) and the results were interpreted and compared with the experimental values. This study shows that there is a significant improvement in the aerodynamic performance of the curved leading edge wing over the wing with rectangular planform.

Research Of Noise In The Unmanned Aerial Vehicle’s Propeller Using Cfd

The major use and need of the multi-rotor UAV in various fields has increased the importance to study the aerodynamics of multi-rotor Unmanned Aerial Vehicles such as the secondary flow over the blade, reduction of noise due to the propeller of the UAV, and the optimization of the design on the propeller with more blades to increase efficiency of the UAV. This paper mainly deals with the reduction of noise which is induced by the propeller. Since there is a demand for compact multi-rotor quite UAV as it has a low probability of detection using radar and infrared but as it generates high drive-line noise caused by propeller it cannot be implemented for some critical applications. As a result, an idea is launched to design a propeller with low drive-line noise levels. A methodology is developed to design a low noise as well as efficient propellers for multi-rotor UAVs. The important parameters like blade thickness, tip loss and blade loading are considered in this research. Also, the effects of propeller important parameters such as activity factor, advance ratio are considered. After the finalization of design consideration of UAV’s propeller and the furthermore noise reduction methodologies also studied such as leading-edge comb, trailing edge tuft, and upper surface porosity in order to generate a perfect UAV for military applications. In order to minimize the noise produced by the propeller the idea of modifying the leading-edges is finalized. Computer-AidedDesign of base propeller and propeller with leading-edge modifications has been generated with the help of CATIA V5 and the acoustic analysis for the static base and propellers with leading-edge modifications with different velocities has been simulated using ANSYS Workbench Fluent 16.2. Finally, a propeller with the leading-edge modification has been found to induce low noise. Keywords: Noise, CFD, Decibel, Propeller, Quite UAV.

Improved aerofoil parameterisation based on class/shape function transformation

ABSTRACTA new aerofoil parameterisation method is put forward to represent an aerofoil by combining the leading edge modification class/shape function transformation (LEM CST) method and improved Hicks–Henne bump function’s method. The new class/shape function transformation (NEW CST) method has two additional basis functions comparing the original CST method. In order to confirm these two basis functions, the radial basis functions neural network (RBF) model is trained by some samples which are generated by the Latin hypercube design (LHD) method and Genetic Algorithm (GA) is proposed to achieve the basis functions of the NEW CST method. The NEW CST method has been evaluated in fitting precision of 1,545 aerofoils by comparison with the LEM CST method and the original CST method. And the improved ability of the NEW CST at the leading edge and trailing edge is verified by a series of complex aerofoil case studies within 1,545 aerofoils. The results indicate that the NEW CST method can represent the whole aerofoils and possesses the intuitive property as well as the original CST. Moreover, the number of control parameters (NCP) to parameterise aerofoils is the fewest among these three methods. Furthermore, when the NCP of the NEW CST and LEM CST is the same, the NEW CST method has the higher accuracy and smaller root mean square errors (RMSE) especially at the leading edge and trailing edge.