Unsteady Aerodynamics - Unsteady Compressibility Effects for Modern Rotorcraft
Abstract
Compressibility effects are known to be a dominant factor in the lift and drag experienced by a helicopter rotor in forward flight, yet very little is known about the underlying physics governing unsteady compressibility effects. Modeling approaches have been developed over the preceding decades to variously describe unsteady aerodynamics and corrections for compressibility effects separately, but these approaches are insufficient for describing combined unsteady compressibility effects from a first-principles standpoint. Thus, the focus of the proposed experimental effort is to study the time-varying characteristics of compressibility on a rotorcraft-relevant airfoil at appropriate conditions matched to flight (Reynolds, Mach, advance ratio, reduced frequency). Experiments will be conducted in Ohio StateÕs 6Ó?22Ó Unsteady Transonic Wind Tunnel, which can produce oscillations of the freestream compressible Mach number and pitch oscillations at rates up to 20 Hz. The specific focus of this work will be a detailed, time-accurate analysis of the wake structure. Time-varying compressibility effects are anticipated to alter the shedding and roll-up of vorticity, distort the spacing of shed structures, and attenuate the upstream propagation of information to the airfoil. These combined effects are anticipated to be the root cause of substantial departures of unsteady loading from the incompressible case. The culmination of this experimental study will result in data that can be coupled with existing or new analytical or reduced order models for enhanced physical insight into unsteady compressibility effects. The knowledge gleaned from this study is critical insight needed for designing the next generation of future vertical lift capability envisioned by the US Army.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 31, 2017
- Source ID
- W911NF1710110
Entities
People
- James W Gregory
Organizations
- Army Contracting Command
- Ohio State University
- United States Army