Browsing by Subject "flight test"
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Item Aerodynamic Design for Swept-wing Laminar Flow(2013-11-08) Belisle, Michael JosephThis work describes and compares processes for swept-wing laminar flow control (SWLFC) aerody-namic design. It focuses on results obtained during the preliminary outer-mold-line (OML) design of the Subsonic Aircraft Roughness Glove Experiment (SARGE), a natural laminar flow and passive laminar flow control wing glove flight experiment funded by the NASA Environmentally Responsible Aviation initiative. The experiment seeks to raise the technology readiness level of the spanwise-periodic discrete roughness element (DRE) SWLFC technique for transition delay on a swept wing. Changes to the SARGE project requirements necessitated numerous redesigns that lead to design process insights and reinforced the value of proven methodologies. Optimization-based wing design methods are compared to traditional processes in the context of issues specific to SWLFC design. A refined traditional process incorporates the lessons learned during SARGE design excursions. As 3D e?ects are often significant at transonic Mach numbers, they should be included in the analysis as soon as practical when allowing for available computational tools. In the initial experimental feasibility and OML design, Euler computational fluid dynamics was used to produce a series of 2.5D SWLFC airfoils with boundary-layer stability and transition predicted using linear stability theory and the e^(N) method. Two wing gloves were lofted onto the Gulfstream-III host aircraft wing: TAMU-05-04, a straight loft using the TAMU2D-04 airfoils, and TAMU-06-05, an optimized revision used in the preliminary design review (PDR) of the SARGE experiment conducted in June 2012. The target pressure distribution for the TAMU-06-05 glove was developed using a graphical B-spline method. The SARGE PDR identified a few issues that need to be addressed in order to ensure a successful experiment, which includes isobar unsweep that adversely a?ects boundary layer stability for DRE control and potential flow separation at the inboard fairing. Using the refined process, an alternate planform is evaluated as a potential starting point to address these issues and is shown to be feasible.Item Laminar Flow Control Flight Experiment Design(2012-11-29) Tucker, Aaron 1975-Demonstration of spanwise-periodic discrete roughness element laminar flow control (DRE LFC) technology at operationally relevant flight regimes requires extremely stable flow conditions in flight. A balance must be struck between the capabilities of the host aircraft and the scientific apparatus. A safe, effective, and efficient flight experiment is described to meet the test objectives, a flight test technique is designed to gather research-quality data, flight characteristics are analyzed for data compatibility, and an experiment is designed for data collection and analysis. The objective is to demonstrate DRE effects in a flight environment relevant to transport-category aircraft: [0.67 ? 0.75] Mach number and [17.0M ? 27.5M] Reynolds number. Within this envelope, flight conditions are determined which meet evaluation criteria for minimum lift coefficient and crossflow transition location. The angle of attack data band is determined, and the natural laminar flow characteristics are evaluated. Finally, DRE LFC technology is demonstrated in the angle of attack data band at the specified flight conditions. Within the angle of attack data band, a test angle of attack must be maintained with a tolerance of ? 0.1? for 15 seconds. A flight test technique is developed that precisely controls angle of attack. Lateral-directional stability characteristics of the host aircraft are exploited to manipulate the position of flight controls near the wing glove. Directional control inputs are applied in conjunction with lateral control inputs to achieve the desired flow conditions. The data are statistically analyzed in a split-plot factorial that produces a system response model in six variables: angle of attack, Mach number, Reynolds number, DRE height, DRE spacing, and the surface roughness of the leading edge. Predictions on aircraft performance are modeled to enable planning tools for efficient flight research while still producing statistically rigorous flight data. The Gulfstream IIB aircraft is determined to be suitable for a laminar flow control wing glove experiment using a low-bank-angle-turn flight test technique to enable precise, repeatable data collection at stabilized flight conditions. Analytical angle of attack models and an experimental design were generated to ensure efficient and effective flight research.Item Laminar-Turbulent Transition Due to 2-D Excrescences at 1% Chord on a Swept Wing(2015-01-22) Crawford, Brian KeithLaminar flow has the potential to dramatically reduce fuel consumption and/or extend the range of modern aircraft. However, before laminar-flow aircraft can be made practical, the effect of surface imperfections must be better understood. Many studies have been performed on the effects of distributed roughness and other types of imperfections. Two-dimensional step excrescences, however have not been studied in significant detail until recently. Two-dimensional steps are common on real aircraft due to practical considerations such as skin-panel junctions, high-lift-device interfaces, deicing mechanisms, etc. Traditionally, these 2-D excrescences have been treated as just another form of roughness; however, the behavior of these steps is fundamentally distinct. The present study tests the effect of 2-D excrescences near 1% chord in order to examine the effects of pressure gradient and curvature. Testing on a 30? swept-wing model is performed in both the flight environment aboard a Cessna O-2A Skymaster, as well as in the Klebanoff-Saric Wind tunnel at Texas A&M University. In both environments, IR thermography is utilized to detect the global laminar?turbulent transition location. In the wind tunnel, a hotwire traverse is also utilized to map out the boundary layer and further measure the influence of these excrescences. Interactions between the crossflow instability and these excrescences are observed. Both critical and subcritical step induced transition behavior is present. Comparisons are made to other contemporary experiments in order to draw conclusions about the influence of pressure gradient, sweep, and curvature on the step-induced transition behavior. The resulting data are intended for use in validating an ongoing companion computational effort.