1,721,106 research outputs found
Aerodynamic Blade Design with Multi-Objective Optimization for a Tiltrotor Aircraft
Full text linkPurpose - The purpose of this paper is to present the aerodynamic blade design of a tiltwing aircraft with a multi-objective optimization procedure. The aerodynamic design of tiltrotor blades is a very challenging task in the project of this type of aircraft. Design/methodology/approach - Tiltrotor blades have to give good performance both in helicopter and aeroplane modes. According to the design parameters (the chords, the twists and the airfoils along the blade), as the optimization objectives are different from one operating condition to another, the blade is the result of a multi-objective constrained optimization based on a controlled elitist genetic algorithm founded on the NSGA-II algorithm. The optimization process uses a BEMT solver to compute rotor performance. To avoid negative effects due to compressibility losses in aeroplane mode, the blade shape has been refined following the normal Mach number criterion. Findings - It has been found that the optimized rotor blade gives good performance both in terms of figure of merit and propulsive efficiency if compared with experimental data of existing rotor (ERICA tiltrotor) and propeller (NACA high-speed propeller). Practical implications - The optimization procedure described in this paper for the design of tiltrotor blades can be efficiently used for the aerodynamic design of helicopter rotors and aircraft propellers of all typology. Originality/value - In this work, advanced methodologies have been used for the aerodynamics design of a proprotor optimized for an aircraft which belongs to the innovative typology of high-performance tiltwing tiltrotor aircraft
Experimental Investigation of the Dynamic Stall Phenomenon on a NACA 23012 Oscillating Airfoil
No full textAn extensive experimental investigation was conducted on an oscillating NACA 23012 airfoil to study the flow structures and the consequent performances in dynamic stall conditions. The testing activity involved two different measurement techniques: fast unsteady pressure measurements and particle image velocimetry. The analysis of the experimental data set made possible to achieve a deep insight in the mechanism of the dynamic stall phenomena for the NACA 23012 airfoil in the different dynamic stall regimes. In particular, the flow velocity field measured on the airfoil upper surface described in detail the mechanism of the formation, migration and shedding of strong vortical structures characteristic of the deep dynamic stall. In addition, Gurney flap effects were investigated. The experimental results showed that it would be advantageous to deploy active Gurney flaps to improve helicopter rotor blade performances. The whole set of experimental results can be considered as a reference to validate computational fluid dynamics tools
Prediction of Aerodynamic Propeller/Wing Interaction with a Panel Code Using Embedded Actuator Disk Model
No full textAssessment of a Propeller Model Embedded on a Panel Method Code for Aircraft Aerodynamics
No full textAn inviscid actuator disk model is embedded in a three-dimensional low-order panel method code for inviscid incompressible ow in order to study the propeller effects on an arbitrary body. The actuator disk model predicts the time-averaged induced velocities in the slipstream of a propeller with an arbitrary radial distribution of load. The model is constructed by superposition of four vorticity distributions, by neglecting the radial contraction of the vortex tube and assuming a fixed wake for the propeller. Experimental data, available from the licterature, have been used to validate the actuator disk model embedded in the panel method code
Aerodynamic Shape Optimisation of a Proprotor and Its Validation by Means of CFD and Experiments
Get PDFThe aerodynamic shape design of a proprotor for a tiltrotor aircraft is a very complex and demanding task because it has to combine good hovering capabilities with high propeller efficiency. The aim of the present work is to describe a two-level procedure and its results for the aerodynamic shape design of a new rotor blade for a high-performance tiltwing tiltrotor aircraft taking into account the most important flight conditions in which the aircraft can operate. Span-wise distributions of twist, chord and aerofoil were chosen making use of a multi-objective genetic optimiser that worked on three objectives simultaneously. A non-linear sweep angle distribution along the blade was designed to reduce the power losses due to compressibility effects during axial flight at high speed. During the optimisation process, the aerodynamic performance of the blade was evaluated with a classical two-dimensional strip theory solver. The optimised blade was than analysed by means of a compressible Navier-Stokes solver and calculations were validated comparing numerical results with experimental data obtained from wind-tunnel tests of a scaled model of the proprotor
Perpendicular blade–vortex-interaction over an oscillating airfoil in light dynamic stall
Full text linkAn experimental and numerical study was performed to investigate the effects of perpendicular blade vortex interactions on the aerodynamic performance of an oscillating airfoil. The selected test cases studied the aerodynamic interaction of a stream-wise vortex impacting on a NACA 23012 airfoil oscillating in light dynamic stall regime, representing a typical condition of the retreating blade of a helicopter in forward flight. The analysis of particle image velocimetry surveys and time-accurate simulation results enabled to point out the different effects due to the blade pitching motion on the interacting flow field. Thus, numerical results enabled to achieve a detailed insight about the aerodynamic loads acting on the oscillating airfoil in the interacting cases. In particular, the comparison with the clean airfoil case shows that a severe loss of performance is produced by the interaction of the vortex during the airfoil downstroke motion, as the vortex impact triggers the local stall of the blade section
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