Unsteady Freestream Velocity Oscillation System at Rotorcraft-Relevant Mach Amplitude
Abstract
The proposed instrumentation and system upgrade to the Ohio State University 6Ó ? 22Ó Unsteady Transonic Wind Tunnel will augment current and future DoD-funded research investigations into unsteady compressible fluid dynamics, including dynamic stall. Recent and ongoing investigations encompass high fidelity, non-intrusive flow measurement and first-ever implementation of phase-locked flow control for pitch and Mach oscillations relevant for a helicopter in forward flight. This wind tunnel has the unique capability to set Reynolds number and Mach number independently through controlling the mass flow and establishing a variable area ratio to choke the flow to a desired Mach number in the test section. Several facility limitations currently prevent the facility from reaching its full potential: (1) The current oscillating choke vanes are designed to achieve a Mach amplitude ÀM < 0.1 which limits the tunnelÕs applicability to experimental modeling of rotorcraft operating below 100 KIAS. (2) Tunnel vibration during unsteady flow evaluations affect PIV laser delivery consistency and prevent time-resolved flow visualization. (3) The confined tunnel test section area limits the pressure tap density near the leading edge of test airfoils which inhibits precise calculation of airfoil loads. The proposed instrumentation and wind tunnel system upgrade will address these limitations by enabling high fidelity airfoil load measurements as well as time-resolved flow visualization studies at realistic rotorcraft Reynolds numbers at 230 KIAS cruise (ÀM = 0.35). This proposal outlines recent unsteady dynamic stall research, a summary of the facility limitations and impact on flow physics, and details the solutions designed to mitigate these shortcomings so that this national unsteady compressible flow asset can reach its full potential.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 07, 2018
- Source ID
- W911NF1710379
Entities
People
- James W Gregory
Organizations
- Army Contracting Command
- Ohio State University
- United States Army