نوع مقاله : یادداشت فنی
نویسندگان
دانشکده مهندسی هوافضا - دانشگاه صنعتی شریف
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In the present work, a free wake unsteady panel method is used to accurately compute vortical wake and aerodynamic characteristics, including the surface pressure distribution and the blade loading for a hovering helicopter rotor. In addition, the effects of blade thickness on aerodynamic characteristics are investigated, by comparing the results of panel and vortex lattice methods. The main advantage of the panel method over the vortex lattice method is that the thickness of blades can be modeled and, therefore, the results of surface pressure are accurately obtained. In the panel method, the blade surface is covered with a source/doublet distribution and the wake is modeled with a doublet distribution. When the blades rotate, the vortices are shed into the wake and freely moved with a velocity induced by the effects of panels located on the blades and in the wake. The wake can freely deform over time to take its natural shape. The aerodynamic calculations, using the free wake panel method, are performed for a NACA0012 wing, to examine the accuracy and validity of the analysis for a three-dimensional geometry. Then, the aerodynamic analysis of a helicopter rotor in hover, for the tip Mach number $M_{tip}=0.44$ , is performed and the present calculations are compared with available theoretical and experimental results. The present results, based on the panel method, are compared with those of the vortex lattice method, to investigate the effects of blade thickness on the surface pressure distribution, the blade loading and the structure of the vortical wake. The effects of the number of panels and the computational time step on the aerodynamic results and the wake structure are also studied. Finally, the aerodynamic analysis of the rotor blades with twist is performed and the results of the panel and vortex lattice methods are compared with each other.
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