Dynamics of Unsteady Flow past Bluff Bodies with Lofted Bases
Abstract
We propose a comprehensive joint experimental and computational program to analyze the flow in aft regions of bluff bodies with lofted bases, such as those encountered beneath and downstream of cargo aircraft. The resulting unsteady flow structures cause increased drag and can adversely impact operations. We will examine the effect of varying loft upsweep angle and flow speeds ranging from incompressible to mildly compressible conditions. High-resolution three-dimensional spatio-temporal data will be acquired with advanced diagnostic techniques, including planar, stereo and time-resolved Particle Image Velocimetry, as well as Large-Eddy Simulations and tailored Reynolds-Averaged Navier-Stokes methods. The data will be processed to focus on different aspects of multi-scale non-linear phenomena in the wake. Of particular interest is large-scale unsteadiness arising after unsteady separation around the periphery of the configuration. Thisincludes localized features such as Kelvin-Helmholtz (K-H) instabilities and subsequent roll-up, pairing, entrainment and intermittency. Causal mechanisms leading to global behavior, including helical and mixed modes, and their influence on meandering phenomena will also be examined, as will energy interactions between large and small scales in the flow. The techniques to obtain these insights include topological analyses, advanced data decompositions that resolve both energy and spectral details, stability studies of both 2-D projections and 3-D mean flows, as well as the time-local linear response of the turbulent flow. The effort will result in a clear understanding of local and global mechanisms, as well as their linkage, that result in the observed phenomena of interest.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 02, 2017
- Source ID
- FA95501710228
Entities
People
- Datta Gaitonede
Organizations
- Air Force Office of Scientific Research
- Ohio State University
- United States Air Force