Aerofoil Shape Research Articles

The modified design of aeroplane fuselage to overcome drag resistance acting due to flow of air

The design of aeroplane fuselage body is designed by using principle of aerofoil shape. The wings of aeroplane are in perfectly aerofoil shape, but main body is not in perfectly aerofoil shape. Thus increases projecting area for striking of fluid on aeroplane; this result into large drag force acting on the aeroplane. This paper is related with external design of aeroplane, describes the use of pipes with decreasing diameter with length. If the bunches of pipes are joined on entire external surface of aeroplane then the drag force due to air reduces with greatest amount and due to decreasing diameter air going through pipe ejects from another end of it and results into creating a force which helps to accelerate the aeroplane. The diameters of pipes are moderated as per cross section area of aeroplane. The drag force acting on the aeroplane is equally distributed to all pipes and its effect to decelerate aeroplane is nullifies with greatest amount. Thus if we implement this arrangement to external design then the total power consumption of aeroplane is greatly reduced.

Computer Analysis of S822 Aerofoil Section for Blades of Small Wind Turbines at Low Wind Speed

The power generated in wind turbine depends on wind speed and parameters of blade geometry like aerofoil shape, blade radius, chord length, pitch angle, solidity, etc. Aerofoil selection is the crucial factor in establishing the efficient wind turbine. More than one aerofoil in a blade can increase the efficiency further. Previous studies of different aerofoils have shown that efficiency of small scale wind turbine increases when NREL S822 aerofoil is used for wind speed on and above 10 m/s. This paper introduces a study on effect of low wind speed (V = 5 m/s) on performance of blade profile. Aerofoils NREL S822/S823 are used for microwind turbine with S823 near root and S822 near tip. Blade of 3 m radius with spherical tubercles over entire span is analyzed considering 5 deg angle of attack. The computational fluid dynamics (CFD) simulation was carried out using ANSYS fluent to study the behavior of blade profile at various contours. The study shows that blade experiences maximum turbulence and minimum pressure near trailing edge of the tip of blade. The region also experiences maximum velocity of the flow. These factors result in pushing the aerofoil in upward direction for starting the wind turbine to rotate at the speed as low as 5 m/s.

A comparative study of controlled random search algorithms with application to inverse aerofoil design

ABSTRACTThis article presents a comparative study of some versions of the controlled random search algorithm (CRSA) in global optimization problems. The basic CRSA, originally proposed by Price in 1977 and improved by Ali et al. in 1997, is taken as a starting point. Then, some new modifications are proposed to improve the efficiency and reliability of this global optimization technique. The performance of the algorithms is assessed using traditional benchmark test problems commonly invoked in the literature. This comparative study points out the key features of the modified algorithm. Finally, a comparison is also made in a practical engineering application, namely the inverse aerofoil shape design.

Automatyzacja definiowania kształtu profili lotniczych w programie AutoCAD

Possibilities of using of CAx systems to automation process of graphical tasks are presented. Possibility of using AutoLISP language with VisualLISP environment to create aerofoil shape in CAx system are analysed.

Geometric Comparison of Aerofoil Shape Parameterization Methods

A comprehensive review of aerofoil shape parameterization methods that can be used for aerodynamic shape optimization is presented. Seven parameterization methods are considered for a range of design variables: class–shape transformations; B-splines; Hicks–Henne bump functions; a radial basis function domain element approach; Bèzier surfaces; a singular-value decomposition modal extraction method; and the parameterized sections method. Because of the large range of variables involved, the most effective way to implement each method is first investigated. Their performances are then analyzed by considering the geometric shape recovery of over 2000 aerofoils using a range of design variables, testing the efficiency of design space coverage with respect to a given tolerance. It is shown that, for all the methods, between 20 and 25 design variables are needed to cover the full design space to within a geometric tolerance, with the singular-value decomposition method doing this most efficiently. A set of transonic aerofoil case studies are also presented, with geometric error and convergence of the resulting aerodynamic properties explored. These results show a strong relationship between geometric error and aerodynamic convergence and demonstrate that between 38 and 66 design variables may be needed to ensure aerodynamic convergence to within one drag and one lift count.

Numerical and experimental validation of a morphed wing geometry using Price-Païdoussis wind-tunnel testing

ABSTRACTAn experimental validation of an optimised wing geometry in the Price-Païdoussis subsonic wind tunnel is presented. Two wing models were manufactured using optimised glass fibre composite and tested at three speeds and various angle-of-attack. These wing models were constructed based on the original aerofoil shape of the ATR 42 aircraft and an optimised version of the same aerofoil for a flight condition of Mach number equal to 0.1 and angle-of-attack of 0°. The aerofoil's optimisation was realised using an ‘in-house’ genetic algorithm coupled with a cubic spline reconstruction routine, and was analysed using XFoil aerodynamic solver. The optimisation was concentrated on improving the laminar flow on the upper surface of the wing, between 10% and 70% of the chord. XFoil-predicted pressure distributions were compared with experimental data obtained in the wind tunnel. The transition position was estimated from the experimental pressure data using a second derivative methodology and was compared with the transition predicted by XFoil code. The results have shown the agreement between numerical and experimental data. The wind-tunnel tests have shown that the improvement of the laminar flow of the optimised wing is higher than the value predicted numerically.

Drag optimisation of a wing equipped with a morphing upper surface

ABSTRACTThe drag coefficient and the laminar-to-turbulent transition for the aerofoil component of a wing model are optimised using an adaptive upper surface with two actuation points. The effects of the new shaped aerofoils on the global drag coefficient of the wing model are also studied. The aerofoil was optimised with an ‘in-house’ genetic algorithm program coupled with a cubic spline aerofoil shape reconstruction and XFoil 6.96 open-source aerodynamic solver. The wing model analysis was performed with the open-source solver XFLR5 and the 3D Panel Method was used for the aerodynamic calculation. The results of the aerofoil optimisation indicate improvements of both the drag coefficient and transition delay of 2% to 4%. These improvements in the aerofoil characteristics affect the global drag of the wing model, reducing it by up to 2%. The analyses were conducted for a single Reynolds number and speed over a range of angles of attack. The same cases will also be used in the experimental testing of the manufactured morphing wing model.

Influence of Solidity on Vertical Axis Wind Turbines

This paper aims to predict the performance of a VAWT. The H-type Darrieus turbine consists of three straight blades with shape of aerofoil attached to a rotating vertical shaft. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order MUSCL scheme using SIMPLE to couple continuity and momentum equations. A parametric study has been carried out to analyse the solidity effect on the non-dimensional curves so that the range of tip speed ratio of operation could be predicted as well as their self-starting behaviour.

ON THE EFFECT OF SHAPE PARAMETERIZATION ON AEROFOIL SHAPE OPTIMIZATION

The selection of suitable shape parameterization technique is one of the significant factors affecting the fidelity of the solution found during aerofoil shape optimization process. This paper investigates the effect of shape parameterization on an automated aerofoil shape optimization problem. Four well known shape parameterization techniques were considered for study; Bezier curves, Class-Shape function Transformation, Hicks-Henne “Bump” function and polynomial method. A boundary layer panel code was coupled with a surrogate-based multi-objective evolutionary algorithm and implemented within an automatic design loop. The optimization problem was formulated for NACA 0012 aerofoil at 5 degree angle of attack. The main criteria for comparison were based on the number of parameters required by each method for accurate representation of the aerofoil, the ability to find the aerofoil with the best performance within the constrained design space and also the computational cost. Preliminary results show that the optimization process was able to increase the lift-to-drag ratio of the aerofoil by 30%. ClassShape Transformation and Hicks-Henne Bump function were able to find the best aerofoil shape within the design space effectively.

Design of h-Darrieus vertical axis wind turbine

Numerical simulation is used to predict the performance of a Vertical Axis Wind Turbine (VAWT) H-Darrieus. The rotor consists of three straight blades with shape of aerofoil of the NACA family attached to a rotating vertical shaft. The influence of the solidity is tested to get design tendencies. The mesh has two fluid volumes: one sliding mesh for the rotor where the rotation velocity is established while the other is the environment of the rotor. Bearing in mind the overall flow is characterized by important secondary flows, the turbulence model selected was realizable k-epsilon with non-equilibrium wall functions. Conservation equations were solved with a Third-Order Muscl scheme using SIMPLE to couple pressure and velocity. During VAWT operation, the performance depends mainly on the relative motion of the rotating blade and has a fundamental period which depends both on the rate of rotation and the number of blades. The transient study is necessary to characterise the hysteresis phenomenon. Hence, more than six revolutions get the periodic behaviour. Instantaneous flows provide insight about wake structure interaction. Time averaged parameters let obtain the characteristic curves of power coefficient.

Multidisciplinary multifidelity optimisation of a flexible wing aerofoil with reference to a small UAV

The preliminary Multidisciplinary Design and Optimisation of a flexible wing aerofoil apropos a small Unmanned Air Vehicle is performed using a multifidelity model-based strategy. Both the passively adaptive structure and the shape of the flexible wing aerofoil are optimised for best aerodynamic performance under aero-structural constraints, within a coupled aeroelastic formulation. A typical flight mission for surveillance purposes is considered and includes the potential occurrence of wind gusts. A metamodel for the high-fidelity objective function and each of the constraints is built, based on a tuned low-fidelity one, in order to improve the efficiency of the optimisation process. Both metamodels are based on solutions of the aeroelastic equations for a flexible aerofoil but employ different levels of complexity and computational cost for modelling aerodynamics and structural dynamics within a modal approach. The high-fidelity model employs nonlinear Computational Fluid Dynamics coupled with a full set of structural modes, whereas the low-fidelity one employs linear thin aerofoil theory coupled with a reduced set of structural modes. The low-fidelity responses are then corrected according to few high-fidelity responses, as prescribed by an appropriate Design of Experiment, by means of a suitable tuning technique. A standard Genetic Algorithm is hence utilised to find the global optimum, showing that a flexible aerofoil is characterised by higher aerodynamic efficiency than its rigid counterpart. Wing weight reduction is also accomplished when a Multiobjective Genetic Algorithm is adopted.

CERAMIC CORES FOR TURBINE BLADES : A TOOLING PERSPECTIVE

Blade/vane components used in aerospace turbines are of twisted aerofoil shape, made by the process of investment casting, using Ni based super-alloy materials. These castings operate at turbine inlet temperatures (TET) close to the melting point of the alloy, in order to maximize thermal efficiency and thrust of the engine. The castings are made hollow, with intricate features such as turbulator, pin-fin, etc built-in to maximize the effect of heat transfer during forced cooling through internal passages. The hollow geometry in the castings is produced during the investment casting process by using a suitable ceramic core made from Silica or Alumina based mixes. These ceramic cores are high pressure injected by forcing the ceramic mix into dedicated molds or dies. Development of such dies is an involved process by itself, addressing issues right from ceramic mix behavior to manufacturability of the injection mould. The present paper attempts to highlight issues related to tooling development for ceramic cores used in investment cast turbine blade/vane components.

Cavitation inception and simulation in blade element momentum theory for modelling tidal stream turbines

Blade element momentum theory (BEMT) is an analytical modelling tool that describes the performance of turbines by cross-referencing one-dimensional momentum theory with blade element theory. Each blade is discretised along its length and the dynamic properties of torque and axial force are determined. A compatible cavitation detection model is introduced to indicate any cavitating blade elements. Cavitation occurrence is dependent on proximity to the free surface, the incident flow velocity and inflow angle and the blade cross-section aerofoil shape. The shock waves associated with cavitation can significantly damage the blade surface and reduce performance; therefore, this model is a useful addition to BEMT and can be used in turbine design to minimise cavitation occurrence. The results are validated using the cavitation experiment observations.

Selected Engineering Applications of Gradient Free Optimisation Using Cuckoo Search and Proper Orthogonal Decomposition

This paper discusses some engineering applications of gradient free optimisation techniques. This is achieved using the development of the cuckoo search algorithm as a case study. The motivations behind using gradient free algorithms are discussed and illustrated using two specific practical examples. The first involves aerofoil shape optimisation, where it is shown that a modified cuckoo search algorithm performs well when applied both to aerofoil inverse design and aerofoil shape optimisation. This example is then used to discuss the use of reduced order modeling to decrease the computational cost of the optimisation process. We discuss which reduced order modeling techniques based on proper orthogonal decomposition are suitable for these optimisation applications. The second example is that of co-volume mesh optimisation, where it is shown that a modified cuckoo search can significantly outperform alternative non-optimisation and gradient based techniques. We conclude by discussing a number of remaining difficulties which may deter engineers from using gradient free techniques, and suggest ways in which these may be alleviated.

Aerodynamic Design and Finite Element Modelling of Mixed Aerofoil Wind Turbine Blades

Both rotor aerodynamic characteristics and structural performance of the blade are critical to the wind turbine system service life; an accurate loading model of the blade is extraordinary complex due to the complexity of the geometry shape and variety of blade thickness. In this paper, a 10KW fixed-pitch variable-speed wind turbine blade with five different thickness of aerofoil shape along the span of the blade is presented as a case study, main parameters of the wind turbine rotor and the blade aerodynamic geometry shape are determined based on the principles of the blade element momentum (BEM) theory, a specific blade internal structure and layup schedule are designed. Based on the FE method, deflections and strain distributions of the designed blade under extreme wind conditions are numerically predicted. Theoretical and numerical results indicate that aerodynamic characteristics of the designed blade meet the requirement, the tip clearance is sufficient to prevent collision with the tower, and the blade material is linear and safe.

Automated generation of aerofoil characteristics for rotorcraft application

PurposeRotor performance analysis and design are complex due to the wide variation in flow characteristics. Design tools that can rapidly and accurately compute aerofoil data are needed for rotorcraft design and analysis purposes. The purpose of this paper is to describe a process which has been developed that effectively automates the generation of two‐dimensional (2D) aerofoil characteristics tables.Design/methodology/approachThe process associates a number of commercial software packages and in‐house codes that employ diverse methodologies, including the Navier‐Stokes equation‐solving method, the high‐order panel method and Euler equations solved with the fully coupled viscous‐inviscid interaction (VII) method. The paper describes the development of a general automated generation method that extends from aerofoil shape generation to aerofoil characteristic analysis. The generated data are stored in C81 aerofoil characteristics tables for use in comprehensive rotorcraft analysis codes and rotor blade design. In addition, the methodology could be easily applied for fixed‐wing analysis and design, especially for transonic aircraft.FindingsThe method is demonstrated to achieve aerofoil characteristics quickly and accurately in automated process. Calculations for the SC1095 aerofoil section are presented and compared with existing experimental C81 data and previous studies.Practical implicationsThe development of C81 tables is of interest to industry as they seek to update their airfoil tables as new designs. Automated processes to achieve this are helpful and applicable.Originality/valueThe paper presents an effective automated process to generate aerofoil characteristics tables quickly, and accurately.

Variation of ground effect phenomena about downforce generating aerofoils caused by changes in aerofoil shape

The aerodynamic characteristics of bodies in ground effect conditions are an important consideration for road vehicle aerodynamic design and analysis. The particular geometric properties of two aerofoils in ground effect are investigated in this study, using two-dimensional computational fluid dynamics. By comparing the different flow features found for each of the two aerofoils, the important geometric components for optimised ground effect performance are determined. This information is then used to modify the shape of one of the aerofoils, with the aim of producing greater performance characteristics. The modified aerofoil is found to produce greater downforce (while also producing an increase in the drag force), which represents an improvement in the aerodynamic characteristics for this application.

Shape optimisation of preform design for precision close-die forging

Preform design is an essential stage in forging especially for parts with complex shapes. In this paper, based on the evolutionary structural optimisation (ESO) concept, a topological optimisation method is developed for preform design. In this method, a new criterion for element elimination and addition on the workpiece boundary surfaces is proposed to optimise material distribution. To improve the quality of the boundary after element elimination, a boundary smoothing technique is developed using B-spline curve approximation. The developed methods are programmed using C# code and integrated with DEFORM 2D software package. Two 2D case problems including forging of an aerofoil shape and forging of rail wheel are evaluated using the developed method. The results suggest that the developed topology optimisation method is an efficient approach for preform design optimisation.

Development and validation of an efficient direct numerical optimisation approach for aerofoil shape design

AbstractIntelligent shape optimisation architecture is developed, validated and applied in the design of high-altitude long endurance aerofoil (HALE). The direct numeric optimisation (DNO) approach integrating a geometrical shape parameterisation model coupled to a validated flow solver and a population based search algorithm are applied in the design process. The merit of the DNO methodology is measured by computational time efficiency and feasibility of the optimal solution. Gradient based optimisers are not suitable for multi-modal solution topologies. Thus, a novel particle swarm optimiser with adaptive mutation (AM-PSO) is developed. The effect of applying the PARSEC and a modified variant of the original function, as a shape parameterisation model on the global optimal is verified. Optimisation efficiency is addressed by mapping the solution topology for HALE aerofoil designs and by computing the sensitivity of aerofoil shape variables on the objective function. Variables with minimal influence are identified and eliminated from shape optimisation simulations. Variable elimination has a negligible effect on the aerodynamics of the global optima, with a significant reduction in design iterations to convergence. A novel data-mining technique is further applied to verify the accuracy of the AM-PSO solutions. The post-processing analysis, to swarm optimisation solutions, indicates a hybrid optimisation methodology with the integration of global and local gradient based search methods, yields a true optima. The findings are consistent for single and multi-point designs.

Experimental studies on the effect of impeller width on centrifugal compressor stage performance with low solidity vaned diffusers

In an effort to improve the performance of centrifugal compressors, detailed studies were carried out on three different impeller-diffuser configurations covering a wide range of design flow coefficients. These were two-dimensional impellers chosen from a multi-stage compressor series with identical blade geometry. The impeller exit widths covered were 24.5, 18.5, and 11.5 mm, respectively. Extensive experimental studies have been carried out on the chosen stage configurations with parallel walled vaneless diffusers (VLDs) as well as low solidity vaned diffuser (LSD). For all the tested configurations, the aerofoil shape of the diffuser vanes remained same while the diffuser width, setting angle, and solidity were chosen as variables. The performance for each of the stages with LSDs was compared with that of the corresponding VLD. Significant improvement in performance in terms of polytropic efficiency, head coefficient, and static pressure recovery coefficient was observed with LSD vanes as compared with the VLD. Significant improvement in performance was noticed from low flow till design point for all the tested cases. The study revealed that among the tested configurations, there is an optimum width at impeller exit and diffuser for which the performance of the stage was the best. Performance in terms of static pressure recovery coefficient was also evaluated for all the tested configurations and compared. All the studies were conducted for solidity ratio of 0.81. The effect of setting angle on wall static pressure coefficient was also studied at 24° and 28° for the flow coefficients corresponding to 80, 100, and 120 per cent of design flow. Flow surveys at impeller exit for the three cases covering impellers/parallel walled diffusers of different widths have also been carried out to know the flow behaviour in the passage between the impeller and the diffuser.