Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings: Theory and experiment

The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary layer and potential flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible

Aeronautical Engineering: A special bibliography with indexes, supplement 55

This bibliography lists 260 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1975

Measurements of ambipoloar diffusion in helium

"February 7, 1949." Note on Report No. 96 laid in.Bibliography: p. 12.Army Signal Corps Contract No. W36-039-sc-32037. Project No. 102B. Dept. of the Army Project No. 3-99-10-022.Manfred A. Biondi [and] Sanborn C. Brown

Development of a Method to Model an Enclosed, Coaxial Carbon Nanotube Speaker with Experimental Validation

Carbon nanotube (CNT) speakers operate on heat as compared to conventional loudspeakers that operate on vibration. CNT speakers are extremely lightweight, stretchable, flexible, and have high operating temperatures. Due to these advantages, CNT speakers are being considered as a viable replacement option for conventional loudspeakers. One such application is automotive exhaust noise control. The goal of this research is to design an enclosed, coaxial CNT speaker and to develop a modeling method to model this speaker using COMSOL Multiphysics. As part of this research, an enclosed, coaxial CNT speaker was designed and manufactured for automotive exhaust noise control. The first prototype was a proof of concept that the design is feasible, and the speaker works. Two additional prototypes have been developed to improve the manufacturing feasibility and performance. The first task undertaken during the modeling method development has been to create COMSOL models that simulated the CNT film temperature oscillation and the corresponding SPL. The simulation results have been compared with a MATLAB model for a planar CNT speaker. In addition, the SPL generated by the coaxial speaker has been compared with the simulated SPL generated by the CNT speaker. In addition, the performance of the coaxial speaker has been simulated in the presence of flow. Generally, a good correlation has been observed between the experimental SPL and simulated SPL. The models can be improved with the future development of improved material properties

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Fabrication and Measurement of LT-GaAs Photoconductive Antennas and Arrays

This thesis presents the fabrication and measurement of LT-GaAs based terahertz (THz) photo conductive antennas (PCAs) and arrays. The LT-GaAs THz PCAs are fabricated to serve as reference devices to new 2D material black phosphorous (BP) based THz PCAs. The LT-GaAs and BP devices have identical metallic electrodes, allowing for a comparison of emitted THz intensity and bandwidth. All PCAs have been measured using an open bench pulsed time-domain spectroscopy (TDS) system with a usable bandwidth from 0.1-4 THz, pumped with a 780nm Ti:Sapphire femtosecond laser. The results have shown LT-GaAs devices outperforming BP devices in signal amplitude and bandwidth at identical DC bias voltages and pump powers. Three other electrode shape designs were achieved: circular, slotted, and fractal, fabricated on LT-GaAs. The effect of electrode shape on the amplitude and bandwidth of the THz pulse has been experimentally characterized. A comparison of all four shapes has shown that the bowtie electrodes provide a nominal increase in pulse amplitude under identical biasing conditions. Further, a polarization study using an x-cut quartz rotator was conducted, validating that all four electrode shapes are highly linearly polarized. Results show that the co-polarized THz pulse is two orders of magnitude greater than the cross-polarized THz pulse. In addition, two element THz PCAs with electrode spacings of 75µm, 150µm, and 300µm have been investigated. A novel feed network using two beam splitters has been designed, and implemented into the existing open bench TDS system. This feed network gives individual control over the position and path length of the beams feeding each elements. Further, a DC bias splitting PCB and switchboard were designed to allow each element to be turned on and off, aiding in laser alignment validation. The measurement of all three devices have shown the array THz pulse having a higher amplitude than either individual element, however, an insignificant effect on the array bandwidth has been observed

Design of a compliant wheel for a miniature rover to be used on Mars

The Jet Propulsion Laboratory has identified the need for a compliant wheel for a miniature martian rover vehicle. This wheel must meet requirements of minimum mass, linear radial deflection, and reliability in cryogenic conditions over a five year lifespan. Additionally, axial and tangential deflections must be no more than 10 percent of the radial value. The team designed a wheel by use of finite element and dimensionless parameter analysis. Due to the complex geometry of the wheel, a finite element model describing its behavior was constructed to investigate different wheel configurations. Axial and tangential deflections were greatly reduced but did not meet design criteria. A composite material was selected for its high strength, toughness, fatigue resistance, and damping characteristics. The team chose a Kevlar fiber filled thermoplastic composite. This report is divided into four primary sections. First, the introduction section gives background information, defines the task, and discusses the scope and limitations of the project. Second, the alternative designs section introduces alternative design solutions, addresses advantages and disadvantages of each, and identifies the parameters used to determine the best design. Third, the design solution section introduces the methods used to evaluate the alternates, and gives a description of the design process used. Finally, the conclusion and recommendations section evaluates the wheel design, and offers recommendations pertaining to improvement of the design solution

Fabrication and Measurement of LT-GaAs Photoconductive Antennas and Arrays

This thesis presents the fabrication and measurement of LT-GaAs based terahertz (THz) photo conductive antennas (PCAs) and arrays. The LT-GaAs THz PCAs are fabricated to serve as reference devices to new 2D material black phosphorous (BP) based THz PCAs. The LT-GaAs and BP devices have identical metallic electrodes, allowing for a comparison of emitted THz intensity and bandwidth. All PCAs have been measured using an open bench pulsed time-domain spectroscopy (TDS) system with a usable bandwidth from 0.1-4 THz, pumped with a 780nm Ti:Sapphire femtosecond laser. The results have shown LT-GaAs devices outperforming BP devices in signal amplitude and bandwidth at identical DC bias voltages and pump powers. Three other electrode shape designs were achieved: circular, slotted, and fractal, fabricated on LT-GaAs. The effect of electrode shape on the amplitude and bandwidth of the THz pulse has been experimentally characterized. A comparison of all four shapes has shown that the bowtie electrodes provide a nominal increase in pulse amplitude under identical biasing conditions. Further, a polarization study using an x-cut quartz rotator was conducted, validating that all four electrode shapes are highly linearly polarized. Results show that the co-polarized THz pulse is two orders of magnitude greater than the cross-polarized THz pulse. In addition, two element THz PCAs with electrode spacings of 75µm, 150µm, and 300µm have been investigated. A novel feed network using two beam splitters has been designed, and implemented into the existing open bench TDS system. This feed network gives individual control over the position and path length of the beams feeding each elements. Further, a DC bias splitting PCB and switchboard were designed to allow each element to be turned on and off, aiding in laser alignment validation. The measurement of all three devices have shown the array THz pulse having a higher amplitude than either individual element, however, an insignificant effect on the array bandwidth has been observed

Aerodynamic Analyses Requiring Advanced Computers, part 2

Papers given at the conference present the results of theoretical research on aerodynamic flow problems requiring the use of advanced computers. Topics discussed include two-dimensional configurations, three-dimensional configurations, transonic aircraft, and the space shuttle