Experimental Investigation of A Helicopter Rotor Hub Flow

Open Access
Author:
Reich, David B
Graduate Program:
Aerospace Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 01, 2017
Committee Members:
  • Sven Schmitz, Dissertation Advisor
  • Sven Schmitz, Committee Chair
  • Mark David Maughmer, Committee Member
  • Philip John Morris, Committee Member
  • Arnold Anthony Fontaine, Outside Member
Keywords:
  • Helicopter
  • Rotorcraft
  • Aerodynamics
  • Rotor Hub
  • Hub Drag
  • Rotor Hub Drag
  • Rotorcraft Aerodynamics
  • Rotorcraft Aeromechanics
  • Unsteady Aerodynamics
Abstract:
The rotor hub system is by far the largest contributor to helicopter parasite drag and a barrier to increasing helicopter forward-flight speed and range. Additionally, the hub sheds undesirable vibration- and instability-inducing unsteady flow over the empennage. The challenges associated with rotor hub flows are discussed, including bluff body drag, interactional aerodynamics, and the effect of the turbulent hub wake on the helicopter empennage. This study was conducted in three phases to quantify model-scale rotor hub flows in water tunnels at The Pennsylvania State University Applied research lab. The first phase investigated scaling and component interaction effects on a 1:17 scale rotor hub model in the 12-inch diameter water tunnel. Effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and wake shed from the rotor hub were quantified using load cell measurements and particle-image velocimetry (PIV). The second phase focused on flow visualization and measurement on a rotor hub and rotor hub/pylon geometry in the 12-inch diameter water tunnel. Stereo PIV was conducted in a cross plane downstream of the hub and flow visualization was conducted using oil paint and fluorescent dye. The third phase concentrated on high accuracy load measurement and prediction up to full-scale Reynolds number on a 1:4.25 scale model in the 48-inch diameter water tunnel. Measurements include 6 degree of freedom loads on the hub and two-component laser-Doppler velocimetry in the wake. Finally, results and conclusions are discussed, followed by recommendations for future investigations.