Interaction of active flow control and global instability
Abstract
When an aerodynamic body undergoes flight maneuvers in o~-design conditions, flow separation can adversely impact its aerodynamic performance. Active flow control can play an important role in modifying the behavior of the surrounding flows to achieve improvement in terms of lift enhancement, drag reduction, fuel efficiency, and enhanced maneuverability of the flying vehicle. The challenges in modifying or controlling the behavior of fluid flow stem from the rich dynamics that fluid flows possess over a wide range of temporal andspatial scales, especially for high Reynolds number flows. While there has been tremendous development in the field of nonlinear dynamics and control theory, the available theories are still limited to small and moderate sized problems. The high-dimensional (if not infinite dimensional) fluid flow systems pose a challenge in controlling the flows in a predictable and robust manner. Hence, the proposed project aims to extract the features of the flow that contribute to the dominant stability characteristics and understand how they interact withforcing inputs in altering the mean flow profile.The objective of the proposed effort is to uncover the interaction mechanismbetween active flow control input and the global instability modes in externalflow over a canonical airfoil geometry. To achieve the goals of this study, wewill examine the flow field with global stability analysis and resolvent analysis,whose results will be examined in detail using a novel network theoretic approach to highlight the interactions and the causal relationship in the flow field. The use of network analysis in this proposed project will reveal the missing links between the stability modes and how they interact with external forcing to modify the mean flow field that predominantly determines the performance of aerodynamic bodies. The formulation proposed here is general in nature and can consider the interaction between hydrodynamic instability modes and flow control forcing inputs or perturbations in the flow, in the form of atmospheric fluctuations or vortical disturbances. Such formulation at the moment is largelymissing when analyzing large-scale fluid flow data sets and can provide a broader impact on the fluid mechanics community at large.The analytical toolsets developed from this study and the resulting physical insights into the fluid flow will enhance our present capability of aerodynamic design and active flow control technologies. If successful, the output from the current investigation will enable engineers and scientists to understand how active flow control inputs and external perturbations can alter the mean flow which directly influences the performance of aerodynamic bodies, such as wings. As we aim for our next-generation aircraft (and submarines) to achieve higher levels of maneuverability and agility in unsteady environments with large-scale disturbances, the use of flow control and the underlying flow physics become ever more important. The proposed investigation may offer critical insights into how fluid flows are altered by external forcing and disturbance, providing pathways to tame unsteady fluid flow over not only the vehicles employed by the US Navy but also those in service by the Department of Defense.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912460
Entities
People
- Kunihiko Taira
Organizations
- Office of Naval Research
- United States Navy
- University of California, Los Angeles