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Research by Jonathan Naughton
Hybrid Control of Jet Flows
Dr. Jonathan Naughton and Dr. Douglas Smith, Air Force Office of Scientific Research, 2000-present, $280,000
An investigation of the elements required for hybrid control of an incompressible jet flow has been carried out over the past two years. The goal of this work is to combine active and passive control methods to produce a greater amount of control than is possible by either method alone. In this study, we are investigating using swirl and zero-mass-flux jets for controlling a jet flow.
A mean-flow characterization of the swirling jet flow has been carried out over the past year and single cross-wire probe measurements are currently underway. The mean flow results indicate that solid-body swirl enhances mixing more than a q-vortex-type swirl. Multiple probe measurements will be carried out next so a low-dimensional model of the jet flow using Proper Orthogonal Decomposition (POD) may be constructed.
Characterization of the mean and turbulent flow fields of a single synthetic jet actuator interacting with a two-dimensional shear layer have been carried out. (Doug Summarize)
A model is currently being fabricated that allows for excitation of the swirling jet by four synthetic jets. This model will be tested early in 2003.
Base Drag Reduction for Reentry Vehicles
Dr. Jonathan Naughton, NASA-Dryden Research Center, 1999-2002, $110,000
An investigation of the use of fore-body viscous drag to reduce base drag has been undertaken. A ramp model with a base area was studied. Two different ramp angles (producing two different base heights) and four levels of roughness (producing four levels of viscous drag) were studied. The results indicated that there was no effect of roughness on base pressure (or based drag) in contrast to other results. This result is attributed to the different geometry used in this study. However, the results suggest that an interaction between the boundary layer and turbulent structure in the base area is responsible for the drag reduction in other studies. The ramp model geometry eliminated this interaction, and thus no roughness effect was observed.
As part of this study, the boundary layer in a favorable pressure gradient was characterized. Pressure measurements, oil-film interferometry shear stress measurements, and detailed hot-wire boundary-layer surveys were carried out. Our preliminary analysis indicates that boundary layers in a favorable boundary layer are very sensitive to roughness effects. This is attributed to the slower growth rate of these boundary layers that makes the relative roughness height (k/d) appear larger. Analysis of this data is continuing.
To answer discrepancies found during the first test, a wedge model is being fabricated. This model is balance compatible and can be set a various angle-of-attacks. The model equipped with pressure instrumentation and oil-film interferometry measurements can be made on the surface. The model is also configurable in three different lengths so that the effect of modifying fore-body viscous drag can be studied with or without roughness. Testing with this model will begin in Fall 2002.
Development of a Low-Dimensional Wind Turbine Inflow Turbulence Model
Dr. William R. Lindberg and Dr. Jonathan W. Naughton, Mechanical Engineering
Dr. Robert D. Kelly and Thomas R. Parish, Atmospheric Science
National Renewable Energy Laboratory, 2002-present, $286,000
An investigation of using experimental data sets to develop low-dimensional models of wind inflows into wind turbines is being carried out by faculty in the atmospheric science department and the mechanical engineering department. The goal is to develop a low-dimensional turbulence model that is coupled to a mesoscale atmospheric model and to integrate the resulting model into existing wind turbine performance codes. Existing wind inflow models fail to capture important atmospheric phenomena such as coherent structures and low-level jets that are critical to predicting wind turbine performance and designing the turbines for peak stress events.
Oil-Film Interferometry Shear Stress Measurement
Dr. Jonathan W. Naughton, 1995-present
Dr. Jonathan W. Naughton (ME) and Dr. Farhad Jafari (MATH), NASA-Ames Research Center, 1999-2001, $40,000
The continued development and application of oil-film interferometry skin-friction measurements is an ongoing effort. Example projects are automatic detection of fringe patterns and development of a GUI to simplify data analysis. Currently, the use of oil-film interferometry as a standard for evaluating static shear stress measurement capability of other shear stress measurement techniques is being considered.
High-Frequency Pulsed Supersonic Micro-Jet Actuators
Dr. Jonathan W. Naughton, Dr. William R. Lindberg, and Dr. David E. Walrath, 2001-present
A preliminary investigation of developing a high-frequency pulsed supersonic jet actuator has been carried out. Preliminary results indicate that jets with 50% duty cycles at 300 Hz are feasible. A new design with an exit diameter of 250 mm is currently under study. Characterization of these extremely small time dependent flows is being carried out using a phase-locked micro-Schlieren flow-visualization system.
Wyoming Active Aero Center
Initial Members:
Dr. William Armstrong, Dr. Jonathan W. Naughton, Dr, William R. Lindberg, Mechanical Engineering
Dr. John E. McInroy, Electrical Engineering
The development of a center focusing on active control of aerodynamic flows using high-bandwidth actuators is underway. The faculty in this center have expertise in aerodynamics, smart materials, mechatronic systems, and control theory. They plan to use their combination of expertise to address interdisciplinary topics such as aerodynamic flutter control, sensor-actuator system development, and control of turbulent flows. In addition to their respective laboratories including a wind tunnel, smart materials lab, and controls lab, the center has access to a highly-maneuverable flight test vehicle. The flight-test vehicle provides a test platform with unique aerodynamic test capabilities (i.e. maneuvering, flight Reynolds number testing) and ensures that active control systems developed for aircraft are flight relevant.