Flow Physics and Nonlinear Dynamics of Natural and Perturbed Turbulent Separation Bubbles
Abstract
The proposed effort will employ a multi-modal approach to study the flow physics andnonlinear dynamics of turbulent separation bubbles (TSBs), which occur when a turbulentboundary layer (TBL) separates from the wall and reattaches further downstream. We will focuson both natural (unperturbed) as well as perturbed TSBs produced by an adverse pressuregradient(APG), yet devoid of configuration-dependent curvature effects, with the particularobjective of gaining physical insights required for the future development of efficient, flowphysicsbased control strategies. Our specific objectives are to employ: (1) wind-tunnelexperiments to induce separation of a turbulent boundary layer (103 < Re? < 104) and subsequentreattachment on a flat plate model; (2) simulations (DNS for Re? < 500, wall-resolved LES for500 < Re? < 1500, and a new wall-modeled LES approach for Re? > 1500) to providedata/insights that complement the experiments; (3) dynamical systems modeling employingExtended Dynamic Mode Decomposition and Resolvent Analysis to explore the flow-physicsand nonlinear dynamics underlying the appearance and scaling of distinct time-scales observed;(4) explore various methods to perturb the TSB in a controlled manner to dissect the nonlineardynamics. Studying the TSB under the effect of controlled perturbations will elucidate themechanisms that generate and govern the observed breathing and shedding modes, reveal theirnonlinear coupling, and provide strategies for future effective control efforts. In the currentstudy, unsteady perturbations will be introduced by modulating the APG as well as oscillating afence upstream of the separation point. Steady perturbations that modify the wall-streak spacingwill also be employed to examine the effect of this feature on the dynamics of the TSB. Finally,sudden initiation and termination of the APG will be used to study the transient response of theTSB.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 28, 2017
- Source ID
- FA95501710084
Entities
People
- Louis N Cattafesta
Organizations
- Air Force Office of Scientific Research
- Florida State University
- United States Air Force