The goal of this research is to investigate aerodynamic performance and high-speed impulsive (HSI) noise of various blade tips for the helicopter's main rotor in forward flight. For this purpose, three-dimensional compressible flow field around the rotor blades is numerically simulated by the solution of the unsteady Reynolds averaged Navier-Stokes (URANS) equations with the "SST k-ω" turbulence model. Solution is quantified by the calculation of torque, drag, and thrust coefficients of C, C, C, and L/D ratio. HSI noise on the rotor plane is assessed by the calculation of sound pressure level at certain points of the flow field using the Ffowcs Williams-Hawking (FW-H) equation. Blade tips are eleven and include anhedral, dihedral, Eagle and combinations of them, and also Blue Edge and rectangular. The combinations are inspired by the tip configurations of the fixed wings. In this regard effects of the tip geometry parameters including curvature and height of its parts have been considered as well. All of the tips are examined for two flight conditions of Caradonna and Tung two-blade rotor with fixed pitch angle and time-varying pitch angles. Based on the present results, it is found that blade tips of dihedral family do not improve the aerodynamic performance of the helicopter blade. Also, addition of anhedral part to the blade tip improves the L/D ratio. According to the present acoustic analysis, it was seen that after the Blue Edge, the Eagle tip stands in order of priority. For the condition of Caradonna and Tung two-blade rotor with tip Mach number of 0.8 and advance ratio of 0.2, HSI noise of the Eagle-tip blade decreases by 2.39 % compared to that of the two-blade rotor with rectangular tip. However, the aerodynamics performance of the Eagle tip is much better than that of the Blue Edge.

中文翻译：

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直升机主旋翼桨叶在向前飞行时使用各种桨尖的数值研究，涉及空气动力学性能和 HSI 噪声考虑


本研究的目的是研究直升机主旋翼向前飞行时各种叶尖的空气动力学性能和高速脉冲 (HSI) 噪声。为此，通过使用“SST k-ω”湍流模型求解非定常雷诺平均纳维-斯托克斯（URANS）方程，对转子叶片周围的三维可压缩流场进行数值模拟。通过计算 C、C、C 和 L/D 比的扭矩、阻力和推力系数来量化解决方案。转子平面上的 HSI 噪声通过使用 Ffowcs Williams-Hawking (FW-H) 方程计算流场某些点的声压级来评估。刀尖有十一个，包括上反角、二面角、鹰形及其组合，还有蓝边和矩形。这些组合的灵感来自固定翼的尖端配置。在这方面，还考虑了尖端几何参数（包括其部件的曲率和高度）的影响。所有叶尖均针对Caradonna和Tung两叶旋翼固定桨距角和时变桨距角两种飞行工况进行了检验。基于目前的结果，发现二面体族叶尖并不能改善直升机桨叶的气动性能。此外，在叶片尖端添加上反角部分可提高长径比。根据目前的声学分析，可以看出，在蓝边之后，鹰尖按优先顺序排列。在Caradonna和Tung两叶旋翼叶尖马赫数为0.8、进速比为0.2的工况下，鹰尖叶片的HSI噪声比矩形叶尖两叶旋翼降低了2.39%。 不过，鹰尖的空气动力学性能比蓝边要好很多。