Boundary-Layer Control, Investigated Using Phenomenological Low-Order Models of Unsteady Flow
Abstract
Unsteady fluid dynamics is ubiquitous in modern research problems involving the design novel air vehicles. These include, micro and nano air vehicles (based on fixed, flapping and rotary wings), high altitude long-endurance aircraft, vertical take-off and landing vehicles, and blended wing-body aircraft. The flow physics in these problems exhibits significant nonlinearities arising from flow separation and vortex shedding. Flow control is a field of engineering aimed at improving efficiencies and performance by altering the natural flow state (in the boundary layer of the wing) to a more desirable state. Experiments and computational fluid dynamics (CFD) have been extensively used to investigate various types of actuators for flow control through parametric studies; however, these haven t helped to develop a design methodology for flow control. Progress in flow control techniques has frequently been achieved by experimentation, experience and luck, and for this reason flow control has been (somewhat mockingly) referred to as an art rather than science in the literature.Low-order models are frequently used in aerospace engineering for design purposes (at least in the preliminary stages), and are a natural fit to enable flow control studies owing to their low time and cost consumption, and their ability to be easily modified-augmented for multidisciplinary problems. However, most low-order models for aerodynamics assume steady flow and there is a lack of reliable low-order models in the (unsteady) regimes where flow control is typically desired.This project aims to study and to develop a design methodology for flow control from a completely unsteady perspective. This will be accomplished through the development and use of new low-order models for 3D unsteady flows. These models are based on phenomenological augmentation of inviscid aerodynamic theory, using numerical computations to account for departures from the assumptions made in theory (such as finite viscosity and flow separation). This approach results notonly the development of low-cost engineering tools for simulation and design, but also the expansion of the literature in unsteady aerodynamic theory and enhanced understanding of the underlying fluid dynamics.The low-order models for unsteady flow introduced through this research will be used to design new aerodynamic parameters that represent the state of the boundary layer. These parameters will be used for defining flow control objectives (such as prevention of flow reversal and separation in the boundary layer). The flow control mechanisms (for altering the boundary layer state) considered in this research will be (i) changes to the wing geometry (via a morphing surface or piezoelectric flaps), and (ii) suction and blowing on the wing surface. This new approach to setting up and solving flow control problems will be applied to selected test problems of current research interest and validated against experiments and computational fluid dynamics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2023
- Source ID
- FA86552117018
Entities
People
- Kiran Ramesh
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Glasgow