TY - JOUR T1 - Numerical investigation of different helicopter main blade tip geometry on aerodynamic coefficients and rotor vortical effects TT - بررسی و شبیه‌سازی عددی اثرات شکل‌های هندسی مختلف نوک پره اصلی بالگرد بر ضرایب آیرودینامیکی و جریان‌های چرخشی حول روتور JF - mdrsjrns JO - mdrsjrns VL - 16 IS - 11 UR - http://mme.modares.ac.ir/article-15-242-en.html Y1 - 2017 SP - 449 EP - 452 KW - Helicopter main blade tip geometry KW - Vortex wake KW - Vortical flows KW - Transonic shock KW - numerical simulation N2 - In this article, the effects of helicopter main rotor blade tip geometric shapes on the aerodynamic of hover flight are analyzed. Aerodynamic coefficients, vortical flows and vortex wakes are discussed. Fluent software with implicit finite volume method has been used for numerical simulation process. The grids are structured. Experimental results of the Caradonna and Tung have been used for aerodynamic validations. In this investigation, the flow has been considered turbulent, compressible, and viscous. The results of several RANS models for a specific rotor have been compared together and finally the standard k-ε turbulent model has been selected. The Roe method with second order scheme was selected. Thirteen different geometrical shapes on the tip of the blades have been presented and the results of the models have been compared together. These studies show that the blades of BERP IV, Blue edge, Actual, Bell-214 and BERP III produce maximum thrust and MIL-17, Sikorsky RH-53D, Tapered, Bell-412, Sikorsky SH-3D and Comanche RAH-66 produce minimum torque and also the blades of BERP III and IV, Ogee and Bell-214 produce maximum torque. M3 ER -