Critical Angle Of Attack Research Articles

Design and testing of three tailless unmanned aerial vehicle configurations built for surveillance in Antarctic environment

The tailless fixed-wing aircraft have a very compact design and therefore are very attractive as portable unmanned aerial vehicle (UAV) platforms. There is a special need for using such platforms in case of operations in such backlands as Antarctica, because very often the equipment necessary for preparing improvised airfields near Antarctic scientific bases and organizing the UAV flights must be hand-carried. The main aim of this paper is to present the design activity and testing of a number of UAV configurations to be used for aerial monitoring in Antarctic areas and collecting data of local ecosystems. Two UAV flying-wing platforms – MONICA-1 and MONICA-2 – were developed, differing largely with respect to wing-loading and weight-to-power ratios. The light-weight Skywalker X-8 built from the kit and used as a baseline configuration was adapted for special photogrammetric missions. It was found that the main advantage of such light UAV consists in a very simple take-off system (i.e. bungee), however due to low wing loading a usage of this UAV is limited to the so-called ‘weather windows’ of relatively low wind, which do not frequently occur in Antarctica. MONICA-1 is much less sensitive to gust but as a heavy platform it is more difficult to handle in harsh Antarctic environment. To be able to operate in much wider range of the wind, vertical gust and heavy turbulence, typical for Antarctic zones, a special UAV platform – called MONICA-2 – was designed and manufactured. MONICA-2 platform of higher wing loading is smaller than the X-8 and at the same time is able to carry the same photogrammetry equipment. The effort of designers focused on achieving low sensitivity to gust and turbulence by increasing the critical angle of attack and natural static and dynamic stability in the whole range of operational speeds. The paper contains the selected design details and some observations from the flight tests.

Numerical investigation of piercing of DP600 within a critical range of slant angle

Deep drawn parts often have complex designs and must therefore be trimmed or punched in a subsequent stage. Due to the complex part geometry, most punching areas have a critical slant angle (angle between part surface and ram movement direction) which differs from the vertical direction. Such piercing within the critical range of the slant angle may lead to severe damage of the cutting tool due to bending effects on the cutting punch. Consequently, expensive cam units are required to transform the ram movement direction in order to perform the piercing process perpendicularly to the local part surface. However, the critical angle of attack described above has not yet been sufficiently investigated for modern sheet metal materials. The purpose of this study is to investigate the influencing factors and their effect on lateral punch deflection during piercing of high strength steel DP600 with slant angles using the FEM Software DEFORM 3D and to create a simulation model that enables a previously sophisticated simulation of the shearing process at different cutting angles. The aim of the study was to measure the lateral deviation of the punch when cutting with a slant angle. The calculated results show that the horizontal deviation is mainly influenced by the slant angle of the workpiece surface, the cutting line and the length of the punch.

A Comparative Study on Hydrodynamic Performance of Double Deflector Rectangular Cambered Otter Board

In the present work, the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment, flume tank experiment and numerical simulation. Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio (KMAX = 3.70). The flow separation occurred when the angle of attack (AOA) was at 45°, which revealed that the double deflector structure of the otter board can delay the flow separation. Numerical simulation results showed a good agreement with experiment ones, and could predict the critical AOA, which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization. However, the drag coefficient in flume tank was much higher than that in wind tunnel, which resulted in a lower lift-to-drag ratio. These may be due to different fluid media between flume tank and wind tunnel, which result in the big difference of the vortexes around the otter board. Given the otter boards are operated in water, it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.

The Migration of Corner Separation Flow in Multi-Channel Compressor Cascades at High Attack Angle

Abstract The corner stall is known as a thorny problem for further increase of aerodynamic load and stability of compressors because of the notable instability separation flow in 3D space. The unsteady flow field in 6 channel rectangle cascades with clearance is studied by numerical simulation of RANS with SST turbulence model and γ-Reθ transition model. The analysis of results shows that with the increase of attack angle, the low energy fluid in the corner region chooses to move along spanwise direction firstly and fluctuates periodically. At critical angle of attack, the low energy fluid adapts to the too large flow drag by breaking through the limitation of local space in identified cascade corner and propagates as a way of unstable stall cells at lateral speed of 27.47% of inlet velocity.

Effect of aspect ratio on hydrodynamic performance of high lift otter board in trawl fisheries

Otter board is one of the main component in the production of single boat trawl fisheries. For improving the expansion performance of trawl net in middle-water trawl fisheries, an improved high lift otter board was developed. A flume model experiment was conducted to measure the lift coefficient (CL), drag coefficient (CD) and lift to drag ratio (K) in different angle of attack (α). The experimental results are as follows: (1) The aspect ratio has significant influence on the max lift coefficient (CLmax), the max lift to drag ratio (Kmax), critical angle of attack (α0) and lift to drag ratio at α0 (P<0.01). As the increase of aspect ratio, the CLmax and Kmax value show a trend of increasing at the beginning and then decreasing, Kα0 value reflects an upward trend, but the α0 reflects a declining trend; (2) The H2 otter board (aspect ratio was 1.4) showed a better hydrodynamic performance. When α=27.5°, CLmax was 2.535, in this case CD = 1.424, K=1.780. When α=10°, Kmax was 3.508, in this case CL = 1.660, CD = 0.473. Suggest the best working scope of angle of attack is between 15°∼30°, in which case, CL>2.053 and K>1.578. The mean value of lift coefficient was 2.356 and the mean of lift to drag ratio was 2.329. Through comparative analysis of the hydrodynamic performance of different types of otter boards, the H2 otter board both had good expansion performance and good expansion efficiency, which can provide a reference basis for further optimization of the bottom trawl otter board.

Leading-edge vortex development on a pitching flat plate with multiple leading edge geometries

This article investigates the dynamic stall of a pitching flat plate in order to facilitate lift control in applications such as flapping wings and micro-aerial vehicles. Constant-pitch-rate rotation, similar to ramp-and-hold, of a flat plate was investigated in an open-jet wind tunnel using embedded surface pressure sensors to assess vortex formation and its impact on aerodynamic characteristics. Three leading edge and trailing edge geometries were investigated, with all demonstrating minor effects on the overall aerodynamic performance for the angles of attack presented. For all leading and trailing edge combinations, increasing the rotation rate increased the magnitude of the localised low pressure on the upper surface the flat plate resulting in increased lift. Separation of the leading-edge vortex was characterised by the motion of a half-saddle flow feature on the upper surface of the flat plate, which in turn was linked to the rotation rate. A critical angle of attack was found whereby further increases in the angle of attack provided no benefit to overall force generation. The surface pressures shown in the current investigation can be utilised for the development of adaptive boundary layer control devices to either limit or promote the dynamic stall process on a flat plates. This study confirms that vortex lift, which is critical for flight of micro-aerial vehicles and flapping wing devices, is limited by the maximum angle of attack and rotation rate. This is significant for high-lift devices where limited power is available for lift generation.

INFLUENCE OF TURBULENCE MODEL ON EXACTNESS CALCULATION OF WING AERODYNAMICS IN SUBSONIC STREAM

The analysis of some modern methods which provide the numerical simulation of the subsonic turbulent viscous flow with the complicated geometrical configuration bodies according to the timeexactness criterion is conducted. The three-dimensional simulation of viscous incompressible flowing around of wing with the profile of NACA-23012 by the finite elements method using six turbulence models is executed. The models used are the model of Spalart-Allmaras, the standard k-e model, Menter model of Shear Stress Transport, the models of Large Eddy Simulation and Detached Eddy Simulation, the model of Scale Adaptive Simulation. Some of these turbulence models features, advantages and disadvantages are mentioned. In the issue of numerical research the diagrams of drag, lift and wing torque coefficients versus the angle of attack in the range of –8 ÷ 26 degrees at the value of Reynolds number 4.4·105 are got. The compared of the expected wing aerodynamic parameters to the results of Central Aero- and Hydrodynamic Institute (TsAGI) experiment is executed. The table of the calculating error values between the wing lift (numerical calculation) and similar data of aerodynamic experiment at the critical angle of attack is put. For the considered class of three-dimensional problems of flow with the complicated geometrical configuration objects by the viscous incompressible flow the models of turbulence which provide the minimum of the calculation time and the maximum of the got results exactness are recommended. Such advisable models are the model of Spalart-Allmaras and k-ω Menter model of Shear Stress Transport.

Aerodynamic Performance and Vibration Analyses of Small Scale Horizontal Axis Wind Turbine with Various Number of Blades

The need to generate power from renewable sources to reduce demand for fossil fuels and the damage of their resulting carbon dioxide emissions is now well understood. Wind is among the most popular and fastest growing sources of alternative energy in the world. It is an inexhaustible, indigenous resource, pollution-free, and available almost any time of the day, especially in coastal regions. As a sustainable energy resource, electrical power generation from the wind is increasingly important in national and international energy policy in response to climate change. Experts predict that, with proper development, wind energy can meet up to 20% of US needs. Horizontal Axis Wind Turbines (HAWTs) are the most popular because of their higher efficiency. The aerodynamic characteristics and vibration of small scale HAWT with various numbers of blade designs have been investigated in this numerical study in order to improve its performance. SolidWorks was used for designing Computer Aided Design (CAD) models, and ANSYS software was used to study the dynamic flow around the turbine. Two, three, and five bladed HAWTs of 87 cm rotor diameter were designed. A HAWT tower of 100 cm long and 6 cm diameter was considered during this study while a shaft of 10.02 cm diameter was chosen. A good choice of airfoils and angle of attack is a key in the designing of a blade of rough surface and maintaining the maximum lift to drag ratio. The S818, S825 and S826 airfoils were used from the root to the tip and 4° critical angle of attack was considered. In this paper, a more appropriate numerical models and an improved method have been adopted in comparable with other models and methods in the literature. The wind flow around the whole wind turbine and static behavior of the HAWT rotor was solved using Moving Reference Frame (MRF) solver. The HAWT rotor results were used to initialize the Sliding Mesh Models (SMM) solver and study the dynamic behavior of HAWT rotor. The pressure and velocity contours on different blades surfaces were analyzed and presented in this work. The pressure and velocity contours around the entire turbine models were also analyzed. The power coefficient was calculated using the Tip Speed Ratio (TSR) and the moment coefficient and the results were compared to the theoretical and other research. The results show that the increase of number of blades from two to three increases the efficiency; however, the power coefficient remains relatively the same or sometimes decreases for five bladed turbine models. HAWT rotors and shaft vibrations were analyzed for two different materials using an applied pressure load imported from ANSYS fluent environment. It has proven that a good choice of material is crucial during the design process.

Periodic and aperiodic flow patterns around an airfoil with leading-edge protuberances

Recently leading-edge protuberances have attracted great attention as a passive method for separation control. In this paper, the effect of multiple leading-edge protuberances on the performance of a two-dimensional airfoil is investigated through experimental measurement of aerodynamic forces, surface tuft visualization, and numerical simulation. In contrast to the sharp stall of the baseline airfoil with large hysteresis effect during AOA (angle of attack) increasing and decreasing, the stall process of the modified airfoil with leading-edge protuberances is gentle and stable. Flow visualization revealed that the flow past each protuberance is periodic and symmetric at small AOAs. Streamwise vortices are generated on the shoulders of the protuberance, leading to a larger separation around the valley sections and a longer attachment along the peak sections. When some critical AOA is exceeded, aperiodic and asymmetric flow patterns occur on the protuberances at different spanwise positions, with leading-edge separation on some of the valley sections and non-stalled condition elsewhere. A combined mechanism, involving both the compartmentalization effect of the slender momentum-enhanced attached flows on the protuberance peaks and the downwash effect of the local stalled region with low circulation, is proposed to explain the generation of the aperiodic flow patterns. The influence of the number of protuberances is also investigated, which shows similar aperiodic flow patterns. The distance between the neighboring local stalled valley sections is found to be in the range of 4–7 times the protuberance wavelength. According to the proposed mechanism, it is speculated that the distance between the neighboring local stalled valley sections is inclined to increase with a smaller protuberance amplitude or at a larger AOA.

Analysis of the Aircraft Motion at the Overcritical Angles of Attack: Errors of On-Board Measurements and Simulation of the Deviated Thrust Vector

The article deals with the problems of the flight test data analysis concerning the flights at higher then critical angles of attack in order to improve the mathematical model of an aircraft's motion. The paper presents a technique for validation and correction of the on-board measurements for this type of motion. Regarding the use of the vector control during such maneuvers, the article considers the mathematical model of the forces and torques generated by the thrust vectoring. Examples of the data processing of the modern maneuverable aircraft's flight tests are presented to confirm the efficiency of the proposed models and methods. The validation of the on-board measurements, above all, the aerometric measurements, is based on the equations of the aircraft spatial motion. It is assumed that the correct values of the motion parameters must satisfy the system of the nonlinear differential equations known from the flight dynamics. This approach has already proved its efficiency in the analysis of the flight data in the operational range of the angles of attack. The signals obtained through the simulation are used to correct the measurements in case of errors. The article presents examples of detection and correction of errors in the measurement channels for a true airspeed and angle of attack. This paper also proposes two versions of the model capable of calculation the projections of the forces and torques on the aircraft principal axes. The first version is derived from the evident geometrical considerations, the second one is based on Rodrigues' vector rotation formula known in the theoretical mechanics. A numerical comparison confirmed correctness of both obtained models. These models were also verified by processing of the flight tests data.

Experimental investigation of piercing of high-strength steels within a critical range of slant angle

Deep drawn parts often do have complex designs and, therefore, must be trimmed or punched subsequently in a second stage. Due to the complex part geometry, most punching areas do reveal critical slant angle (angle between part surface and ram movement direction) different to perpendicular direction. Piercing within a critical range of slant angle may lead to severe damage of the cutting tool. Consequently, expensive cam units are required to transform the ram moving direction in order to perform the piercing process perpendicularly to the local part surface. For modern sheet metals, however, the described critical angle of attack has not been investigated adequately until now. Therefore, cam units are used in cases in which regular piercing with high slant angle wouldn’t be possible. Purpose of this study is to investigate influencing factors and their effect on punch damage during piercing of high strength steels with slant angles. Therefore, a modular shearing tool was designed, which allows to simply switch die parts to vary cutting clearance and cutting angle. The target size of the study is to measure the lateral deviation of the punch which is monitored by an eddy current sensor. The sensor is located in the downholder and measures the lateral punch deviation in-line during manufacturing. The deviation is mainly influenced by slant angle of workpiece surface. In relation to slang angle and sheet thickness the clearance has a small influence on the measured punch deflection.

Effects of aspect ratio on the hydrodynamic performance of full-scale rectangular otter board: Numerical simulation study

In the present work, the hydrodynamic characteristics of full-scale rectangular otter board were studied by numerical simulation, including the effects of aspect ratios (AR), flow distribution around the otter board, induced velocity, induced angle of attack (AOA), effective AOA and induced drag coefficient. It was demonstrated that the otter board had a critical AOA of 40° (when the stall appeared) and induced AOA of 3~10°. The maximum induced drag coefficient was 0.185, which is a great contribution to the total drag coefficient. The otter board exhibited better performance when the AR was set to 0.5, and higher AR had a smaller critical AOA (the stall happened earlier). The maximum lift coefficient decreased with an increasing AR, while the maximum lift-to-drag ratio increased. The induced drag coefficients showed similar trends across ARs, initially rising with an increase of the AOA, and then dropping. The flow distribution around the otter board showed that the wing-tip vortex was fully developed at the AOA of 40°, and the AR can affect the development of the wing-tip vortex.

Mach number effects on buffeting flow on a half wing-body configuration

Purpose The purpose of this paper is to discuss a numerical study of the flow over a wing representative of a large civil aircraft at cruise condition. For each Mach number considered, the numerical simulations indicate that critical angle of attack exists where the separated region increases in size and begins to oscillate. This phenomenon, known as transonic shock buffet, is reproduced by the unsteady simulation and much information can be extracted analysing location, amplitude and frequency content of the unsteadiness. Design/methodology/approach Reynolds-averaged Navier-Stokes simulations are conducted on a half wing-body configuration, at different Mach numbers and angles of attack. Different turbulence models are considered, and both steady-state results and time-accurate simulations are discussed. Findings The high number of cases presented in this study allows the creation of a database which, to the authors’ knowledge, has not been documented in literature before. The results indicate that, while high-fidelity approaches can improve the quality of the results, the URANS approach is capable of describing the main features of the buffet phenomenon. Research limitations/implications The presence of a turbulence model, despite allowing the description of the main unsteady phenomenon, might be insufficient to fully characterise the unsteadiness present in a transonic flow over a half wing-body configuration. Therefore, researchers are encouraged to verify by means of experimental investigation or high-fidelity approach the results issued from a Reynolds-averaged Navier-Stokes equations. Practical implications The results presented clearly indicate that, despite what proposed in recent research papers, transonic buffet can be described by means of time-accurate Reynolds-averaged Navier-Stokes equations. Such an approach is popular in the aeronautical industry because of its reduced costs, and could be used for wing design. Originality/value In this paper, the authors used a classical approach to tackle the known problem of transonic buffet in three-dimensional configurations. The large number of results presented can be used as a database for future numerical simulations and experiments, and allow to describe the flow-physics of the buffet unsteadiness on a half wing-body configuration.

Effect of the Backward-Facing Step Location on the Aerodynamics of a Morphing Wing

Over the last decade, aircraft morphing technology has drawn a lot of attention in the aerospace community, because it is likely to improve the aerodynamic performance and the versatility of aircraft at different flight regimes. With the fast paced advancements in this field, a parallel stream of research is studying different materials and designs to develop reliable morphing skins. A promising candidate for a viable morphing skin is the sliding skin, where two or more rigid surfaces remain in contact and slide against each other during morphing. The overlapping between each two panels create a backward-facing step on the airfoil surface which has a critical effect on the aerodynamics of the wing. This paper presents a numerical study of the effect of employing a backward-facing step on the suction side of a National Advisory Committee for Aeronautics (NACA) 2412 airfoil at a high Reynolds number of 5.9 × 106. The effects of the step location on the lift coefficient, drag coefficient and critical angle of attack are studied to find a favorable location for the step along the chord-wise direction. Results showed that employing a step on the suction side of the NACA 2412 airfoil can adversely affect the aforementioned aerodynamic properties. A drop of 21.1% in value of the lift coefficient and an increase of 120.8% in the drag coefficient were observed in case of a step located at 25% of the chord length. However, these effects are mitigated by shifting the step location towards the trailing edge. Introducing a step on the airfoil caused the airfoil’s thickness to change, which in turn has affected the transition point of the viscous boundary layer from laminar to turbulent. The location of the step, prior or post the transition point, has a noteworthy effect on the pressure and shear stress distribution, and consequently on the values of the lift and drag coefficients.

Hydrodynamic characteristics of a supercavitating vehicle’s aft body

The nonlinear and multi-factor-dependent characteristics of the hydrodynamic forces acting on the aft body of a supercavitating vehicle are investigated using computational fluid dynamics (CFD). The CFD model of natural supercavitating flow is first verified and validated upon the supercavitating flow around a cavitator in the shape of a circular disk. Then the model is used to simulate the supercavitating flows over a typical supercavitating vehicle model at different cavitation numbers σ and angles of attack (AOA) α. By analyzing the supercavitating flow patterns and hydrodynamic force curves, the hydrodynamic characteristics of the aft body and their forming mechanisms are revealed: (a) The normal force and pitch moment are mainly generated by the pressure difference between the windward side and leeward side of the cylinder section caused by asymmetrical reattaching of the supercavity. (b) The hydrodynamic coefficients depend on both σ and α nonlinearly. Free AOA αfr and critical AOA αcr are identified to model the nonlinearity of hydrodynamic force about AOA. (c) For the designated model, αfr and αcr depend on supercavitating flow patterns determined by σ. The simulation results and conclusions would be beneficial for more accurate dynamic modeling and control simulation for supercavitating vehicles.

Aerodynamic airfoil at critical angles of attack

Aircraft construction experts must not neglect the behavior of aircraft in extreme or closely extreme flight conditions, such as flights at critical angles of attack, where a normal flight can be easily converted into a stall. This paper highlights the essential factors that influence the behavior of aircraft in flight at critical angles of attack. Based on the available experimental results and estimations, the performances of airfoils were analysed depending on air flow conditions (categorized according to Mach and Reynolds numbers), airfoil shapes, dynamics of the transition of angles of attack, description of the flow around airfoils with increasing the angle of attack upon reaching a critical value, and the effect of roughness of airfoil surfaces at critical angles of attack. The paper gives a physical interpretation of a lift decrease and a stall. It minutely describes the origin of flow separation and categorizes airfoil sections by type of separation and their behavior during the flow at the critical angle of attack. Based on modern aerodynamics, this paper aims to show and explain the issues and the most important characteristics of the flow past the body at critical angles of attack and give practical recommendations for airfoil design. As such, it may be of interest to pilots and engineers as well as to educational and research institutions.

Development of a Paraglide Control System for Automatic Pitch Stabilization to Increase the Passive Safety

Paragliders tend to collapse when entering a too low pitch angle, which can lead to dangerous situations. The aim of this project was to develop a system, which is able to stabilize the pitch axis/movement of a paraglider in order to avoid critical angles of attack and resulting front collapses. A 6 DOF sensor measured these critical pitch values during flight, a microcontroller unit activates linear actuators located in the harness of the pilot, and pulls on the D-risers of the paraglider to stabilize the overshooting. This substitutes the active reaction of a pilot and therefore is able to prevent critical flight situations. For evaluation, pitch values with and without stabilization system, during artificially induced overshooting maneuvers, got compared. The evaluation results showed a distinct influence of the system on the pitch behavior of the canopy proving the successful realization of the concept. This project was a feasibility study in terms of electronic stabilization systems for paragliders. It showed such a system is able to increase the safety of paragliders.

An analytical solution for the galloping stability of a 3 degree-of-freedom system based on quasi-steady theory

The aerodynamic forces on a two-dimensional three-degree-of-freedom (3DOF-heave, sway and torsion) body of arbitrary cross-section are considered, for arbitrary wind direction relative to the principal structural axes. The full 3DOF aerodynamic damping matrix is derived, based on quasi-steady theory, using the commonly-used concept of an aerodynamic centre to represent the effect of the torsional velocity on the aerodynamic forces. The aerodynamic coefficients are assumed to be consistent functions of only the relative angle of attack. It is shown that the determinant of the quasi-steady aerodynamic damping matrix is always zero. The galloping stability of the aerodynamically coupled system is then addressed by formulating the eigenvalue problem, for which analytical solutions are derived for the case of perfectly tuned structural natural frequencies. The solutions define a non-dimensional effective aerodynamic damping coefficient, indicating how stable the system is. A trivial solution always exists, with zero effective aerodynamic damping, corresponding to rotation about the aerodynamic centre, and relatively simple exact closed-form solutions are derived for the other one or two solutions, the minimum solution defining the stability of the system. Example results are presented and discussed for square, rectangular (aspect ratio 3) and equilateral triangular sections and a lightly iced cable, and they are compared with results using previous solutions for 2DOF translational and 1DOF pure torsional galloping. For the shapes considered it is found that the stability of the 3DOF system is normally close to that of the 2DOF translational system, with a relatively small influence of the stability of the torsional degree of freedom, although in some instances, especially at the critical angles of attack, it can significantly affect the stability.

Ensuring the stability and control of the aircraft at critical angles of attack

The aim of this paper is to study the effect of different combinations of structural funds management boundary layer of air on the aerodynamic characteristics of the aircraft, the development of guidelines for the selection of the most successful combination of sagging, vortex, vortex generators, as well as the geometric shape, size, location of the selected funds.To conduct the study were considered layout of the aircraft 'wing + fuselage "burly and turbulence; burly and vortex generators.Scientific novelty lies in the combination of the existing structural funds management boundary layer of air (sagging, vortex, vortex generators) to ensure the best aerodynamic characteristics and parameters of stability and controllability.This article describes the panel and the vortex method of calculating the aerodynamic aircraft required to perform research and development guidelines.Examining the results of calculations, we can say that the most successful combination is a combination of sagging and vortex generators. It can significantly increase the load-bearing properties of the aircraft, especially at the critical angles of attack, the critical angle of attack, as well as the effectiveness of the cross-government. The developed guidelines can be used for any purpose aircraft, of any size.

Computational Analysis of Different Shapes of Dimple on Wing

Dimple is a slight indentation in a surface. Dimples create turbulence by creating vortices which delays the boundary layer separation resulting in decrease of drag, increasing aerodynamic efficiency, manoeuvrability and also the angle of stall. The present work focused on the understanding of the effect of dimples on boundary layer separation, lift, drag, critical angle of attack, aerodynamic efficiency of wings. The airfoils without any dimples and with circular dimples as inward and outward on are studied. Types of dimples considered in 3D studies are circular and octagon dimple then computational analysis is done using ANSYS FLUENT CFD software, applying subsonic flow, in three dimensional co-ordinate system. The results are compared with a straight wing without dimples. Then suggestions and conclusions are made.