Papers by Keyword: Angle of Attack

Abstract: Unmanned aerial vehicles (UAVs) are considered one of the modern technologies that have recently used in many military and civilian applications. This research investigates the aerodynamic stability of the STU.1.M predator drone was studied by studying the change in the values of the lift and drag coefficients and the lift-to-drag ratio using numerical modelling, Computational Fluid Dynamics (CFD) was employed to simulate performance across range of angles of attack (0° to 14°) at various speeds (20, 40, 60, 80 m/sec) under incompressible flow conditions. The engineering model of the aircraft was generated and the numerical validity was confirmed against experimental data from referenced study. The results indicated that the change in the value of the lift and drag coefficients and the lift-to-drag ratio with respect to UAV velocity is with no significant. The results also showed that the value of the lift coefficient and the lift-to-drag ratio increased with the increase in the value of the angle of attack, The maximum L/D ratio of 8.5 was achieved at a 6° angle of attack and speed of UAV 80 m/s, pressure and velocity contours identified stagnation regions with maximum pressure points at the UAV 's nose, wing, and tail.

Abstract: The results of experimental studies of a separate contact dynamic interaction of a spherical non-deformable pellet with a plastic flat metal surface at different angles of attack (20° ≤ α ≤ 90°) at high speeds (v ≈ 100m/s) are presented. A method is described for determining the nature of the viscoelastic resistance of a surface layer attacked by a pellet during contact displacement along the normal to the surface and rigid plastic resistance during tangential displacement, which can be used to establish the processing regimes of products by a mass flow of abrasive particles, in particular, shot-blasting cleaning. The results of comparing the obtained and known theoretical data with each other and with experimental studies are presented.

Abstract: Vertical Axis Wind Turbine (VAWT) can perform better than Horizontal Axis Wind Turbine (HAWT) because VAWTs are relatively simple, quiet, and easy to install. It can take wind from any directions, and operate efficiently in urban areas where turbulent wind conditions usually happen. The weakest point for its configuration, however, is its low efficiency so more intensive research is required.Actual VAWT performance can be predicted based on a determination of the forces acting on blades that produce the turbine’s torque. Thus, this paper proposed a new model of force analysis for calculation of VAWT’s performance and a way to enhance the efficiency of VAWT through proper variations of the pitch angles. Additionally, in order to increase the efficiency of the VAWT for a given tip speed ratio, the solidity in term of blade’s number can be adjusted.Results show that right changes in the value of pitch angles and proper selection of the number of blades can considerably increase the efficiency of the turbine and reduce amplitude of turbine’s torque variation. The new model of force analysis can be helpful for aerodynamic analysis of the VAWT turbine for its better design.

Abstract: 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.

Abstract: Use of NACA 0012 at the Sultan Wind Turbine prototype provide value coefficient power turbine at wind speed 5.5 m / s by 0017 , wind speed 6.1 m / s at 0.015 , wind speed 7.7 m / s at 0.016 , wind speed 6.5 m / s for 0018 and wind speed 6.2 m / s by 0017 . Where the value of the highest efficiency obtained at a speed of 6.5 m / s at 0.018 . This result is not as expected to generate sufficient energy.The next development carried out investigations on some kind of airfoil, from investigations obtained by using Qblade software that NACA 6612 has a value of 1.78 CL at 15 degrees angle of attack is the largest of all the airfoil .In this research, NACA 6612 will be simulated with a variable chord length, angle of attack, and wind speed, of these three variables will be created which will map graphics 3d sliding value of the ratio of the 3 variables, this graph will give recommendations most optimum combination of variables to types are mapped wind speed throughout the year, to produce optimum power.Optimum combination of NACA 6612 with wind speed varied from 2-7 m/s is chord length 30 cm and angle of attack 7 degree.

Abstract: The airflow velocity over blunt sphere is used to calculate ball-nose vehicle's atmospheric parameters about angle of attack, angle of sideslip and flight speed. A final model satisfying compressible flow is developed, and the expressions for atmospheric parameters is derived from three strategically selected sensors' velocity. The expressions of atmospheric parameters are verified through Fluent stimulation. The result of stimulation demonstrates a good accuracy of angles and flight speed, and the system has a good real-time performance.

Abstract: This paper is primarily concentrated with determining aerodynamic characteristics and choosing the best angle of attack at a maximum lift and low drag for the FX 63-137 aerofoil at a low Reynolds number and a speed of 20m/s and 30m/s, by using subsonic wind tunnel through manufacturing the aerofoil by aluminum alloy using a CNC machine. The proposed methodology is divided into several stages. Firstly, manufacturing the aerofoil using an aluminum alloy. Secondly, the testing process is carried out using subsonic wind tunnel. Thirdly, the results are displayed and compared with results produced from related works, in order to find out the best angle of attack at a maximum lift.

Abstract: HAV has a potential application as the new means to carry Ultra Heavy Payload cargo since it combines the buoyancy capabilities of Lighter-than-Air (LTA), and the aerodynamics of lifting body of Heavier-than-Air (HTA) for speed. Due to its potential, American Institute of Aeronautics and Astronautics (AIAA) has issued a Request for Proposal (RFP) regarding the Hybrid Airship Vehicle (HAV) as cargo transportation with several requirements. AIAA RFP required an envelope that can produce 60% of the lift from buoyancy and 40% of lift from aerodynamic. To satisfy the RFP requirements, this paper analyzed 4 different designs using Computational Fluid Dynamic (CFD) software. Design 4 was chosen as the final design because it meets all the requirements. It was found that at 5° Angle of Attack (AOA), the envelope produce highest aerodynamic lift over drag (L/D) ratio of 3.79. At higher AOA, flow separation occurs at the envelope tail section jeopardizing the aerodynamic characteristic of Design 4 envelope. The lift and drag force graphs were plotted at this AOA and it was found that the HAV envelope is capable of performing the tasks in the RFP.

Abstract: Missile airframe experiences large variations in wall temperature along the circumference due to high angle of attack, especially at hypersonic speeds, which leads to large thermal stresses and bending loads. Such a situation with large wall temperature variations occurs due to high angle of attack during flight. Thermal design of the airframe involves the estimation of local flow parameters and heat flux distribution. Kinetic heating analysis has been carried out for the prediction of heat load distribution on missile airframe considering hypersonic flow with high angle of attack for a particular flight trajectory. Out of a set of possible flight trajectories, a trajectory producing minimum circumferential variation in wall temperature, as concluded through kinetic heating analysis, is finalized. Transient three dimensional heat transfer analysis of the airframe is carried out for prediction of wall temperature distribution for proper selection of material of construction of airframe so that it retains its strength at elevated temperatures. Parametric study has been carried out considering various combinations of airframe wall thickness in presence of external thermal protection coating and internal insulation for the finalized trajectory. Based on the present analysis, airframe configuration having axially variable wall thickness corresponding to the selected flight trajectory is finalized. The validation of the methodology adopted for the analysis has been carried out with respect to airframe temperature data acquired during flight.

Abstract: In this paper, when Reynolds number is within the range of 10000 to 1000000, the horizontal component of the total pressure of flow around flat plate at high angle of attack was regarded as lift of high angle of attack, and the vertical component was regarded as drag of high angle of attack. The horizontal component of total pressure at small angle of attack was regarded as shape drag, and the total drag coefficient at small angle of attack was considered to the sum of the shape drag and frictional drag at zero angle of attack. For the two states of large and small angle of attack, the application scopes of the formulas of lift and drag coefficients were given. Final, the relations of lift and drag coefficients were obtained by eliminating all angles of attack. Research results show that lift - drag curve of small angles of attack is parabola, and the lift - drag curve of high angles of attack is circle.