Wind-Tunnel Test of an Articulated Helicopter Rotor Model with Several Tip Shapes.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
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A wind-tunnel investigation has been conducted using an articulated helicopter model rotor system to determine the effects of several blade tip designs on both the performance and acoustic characteristics of the rotor. Only the performance characteristics are presented in this paper. Six tip shapes were tested a square baseline tip, an ogee tip, a subwing tip, a swept tip, a winglet tip, and a short ogee tip. Tests were conducted at two rotor rotational speeds and five advance ratios including hover. In hover at the lower rotational speed and a given lift coefficient, the swept, ogee, and short ogee tips had about the same torque coefficient, and the subwing and winglet tips had a larger torque coefficient than the baseline square tip blades. In simulated forward flight, the ogee tip had values of torque coefficient very close to or less than the baseline square tip blades. In simulated forward flight at 1200 rpm, the ogee tips showed a decrease in torque coefficient relative to the baseline blades as drag coefficient decreased. The swept tip blades required less torque coefficient at lower rotational speeds than the baseline square tip blades and roughly equivalent torque coefficient at higher rotational speeds in forward flight. The short ogee tip was tested in limited forward flight conditions and it required higher torque coefficient at higher lift coefficient than the baseline square tip blade. Author
- Fluid Mechanics