DYNAMICS AND CONTROL OF CARGO AIRCRAFT WAKES WITH BAYS AND DOORS
Abstract
Aft sections of military cargo aircraft fuselages display relatively flat surfaces at high upsweep angles to accommodate ramp doors. Fundamental research on the peculiar features of the resultant wake has focused on near-incompressible flow past a surrogate configuration comprised of a cylinder with freestream-aligned axis and a planar sharp-edged upswept base. The flow is characterized by separation and the emergence of an unsteady, counter-rotating turbulent longitudinal vortex pair exhibiting meandering and hysteresis. This environment raises safety and performance concerns, including potential for paratrooper accidents, cargo drop error, tail strikes and increased drag. In the present work, in the first phase, we build on this foundation to examine flow and configurational parameters that are crucial to cargo aircraft operation, but whose fundamental non-linear dynamics have not been elucidated. For this, we propose to delineate the effects of i) compressibility by considering flow regimes at cruise and active drop speeds, ii) fuselage edge details that permit flapping instabilities and iii) open bay operation, without and with an extended bay door. The fluid phenomena of interest include wake unsteadiness, potential resonant interactions, instability inception growth and downstream signatures, turbulent vortex dynamics including meandering, and drag. In the second phase, we use this understanding to iv) investigate the perturbation sensitivity of the flow to guide and demonstrate a sophisticated control method using a genetic algorithm and microjet actuators, with drag reduction as the primary objective and wake unsteadiness reduction as a secondary objective. A proven synergistic experiment-computation-theoretical strategy is deployed, predicated on proven state-of-the-art high-fidelity techniques, including time-resolved probe- and laser-based 3-D diagnostics and Large-Eddy Simulations. These complementary approaches leverage the strengths of each with sufficient overlap to ensure credibility. The analysis will exploit statistical techniques, data-driven and operator-aware decompositions and system identification techniques, to further evolve a paradigm for control applicable to other complicated 3D flowfields such as flows past high-speed cars and trains.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 07, 2023
- Source ID
- FA95502210103
Entities
People
- Datta V. Gaitonde
Organizations
- Air Force Office of Scientific Research
- Ohio State University
- United States Air Force