円形および楕円形ノズルからの不足膨張噴流に関する解析的研究

The supersonic jet issuing from circular and elliptic exit of convergent-divergent nozzle has been investigated by rainbow schlieren deflectometry and modified linearized model. In experimentally, a design Mach number of 1.5 followed by a cylindrical duct with an inner diameter of 10 mm, and length of 50 mm are considered to measure the density, internal flow features of jet combing with the computed tomography. In theoretically, a modified vortex sheet model taking viscosity into account has been proposed. The properties of Bessel’s and Mathieu functions with the first Fourier mode of eigenvalues are executed for the individual exit geometry to evaluate the explicit solution of inviscid and viscous jet separately. The embodied results of density, shock-cell spacing, and size measuring have also been examined theoretically. In comparison, the accomplished yields are shown better agreement with published data due to the aspect ratios, nozzle pressure ratios and design Mach number arbitrarily.北九州市立大

The aerodynamics of curved jets and breakaway in Coanda flares

An investigation was carried out into external-Coanda Effect flares designed by British Petroleum International plc. The phenomenon of interest was breakaway of an under expanded axisymmetric curved wall jet from the guiding surface due to high blowing pressure. A survey of investigations of similar flows suggested very complex jet fluid dynamics. Strong cell structure including shock waves was present giving bulk and discrete compression and bulk dilatation. More expansion was imposed by the radial velocity components. Wall curvature and a rear-facing step added further significant influences. The combination of these factors is known to produce highly non-linear turbulence, and this constitutes a major difficulty for the application of computational methods to the flare. In view of the amount of resources required to eliminate the problems of using a Navier-Stokes code, an economical approach was adopted, matching the Method of Characteristics to various simplified models and an integral boundary layer. In the experimental work, a planar model of the flare was contructed and studied using a wide range of methods in order to achieve accuracy and provide comparability with other work. An axisymmetric model was designed and investigated in a similar manner, so that the influence of this geometry could be clearly distinguished. A full-scale flare was subjected to a restricted range of tests to compare the laboratory results with the industrial application. The results from all the experiments demonstrated good correspondence. The main conclusion was that amalgamation of separation bubbles is crucial for breakaway. These are present long before breakaway, and are strongly reduced by decreasing the cell scale, adding a rear-facing step and axisymmetry, which leads to improved breakaway performance. Although the computational methods did not prove robust enough for all design purposes, they did permit significant insights into the mechanism of breakaway

Laser, optical and electrical diagnostics of colliding laser-produced plasmas

This thesis describes the development of and results from a new laboratory facility designed to investigate the properties and explore potential applications of colliding laser produced plasmas. When two plasmas collide there are two extreme scenarios that can play out – the plumes can either interpenetrate or stagnate depending on the ion-ion mean free path. During interpenetration, the plasmas stream through each other, the main interaction amounting to binary collisions. In the case of stagnation, rapid accumulation of plasma material at the collision front leads to the formation of a dense layer of material between the two plasmas. Interferometry of single laser produced plasmas created in background gaseous atmospheres expose the presence of a shock front at the plasma gas interface which rapidly expands outwards. Shadowgraphy is currently the most widely employed diagnostic technique to analyse such shock fronts and a comparison of both techniques reveals that interferometry can be used to diagnose the interaction of laser produced plasmas in gaseous environments in pressure regimes where other techniques such as shadowgraphy are not sensitive. Optical diagnostics such as laser interferometry, fast imaging (angularly resolved) and optical emission spectroscopy have been employed to probe colliding plasmas, revealing important factors in the formation of the stagnation layer. For example the studies have found that electrons stagnate before ions and similarly ions stagnate before neutral species

Semiconductor Infrared Devices and Applications

Infrared (IR) technologies—from Herschel’s initial experiment in the 1800s to thermal detector development in the 1900s, followed by defense-focused developments using HgCdTe—have now incorporated a myriad of novel materials for a wide variety of applications in numerous high-impact fields. These include astronomy applications; composition identifications; toxic gas and explosive detection; medical diagnostics; and industrial, commercial, imaging, and security applications. Various types of semiconductor-based (including quantum well, dot, ring, wire, dot in well, hetero and/or homo junction, Type II super lattice, and Schottky) IR (photon) detectors, based on various materials (type IV, III-V, and II-VI), have been developed to satisfy these needs. Currently, room temperature detectors operating over a wide wavelength range from near IR to terahertz are available in various forms, including focal plane array cameras. Recent advances include performance enhancements by using surface Plasmon and ultrafast, high-sensitivity 2D materials for infrared sensing. Specialized detectors with features such as multiband, selectable wavelength, polarization sensitive, high operating temperature, and high performance (including but not limited to very low dark currents) are also being developed. This Special Issue highlights advances in these various types of infrared detectors based on various material systems

NASA Tech Briefs, February 1996

Topics covered include: Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Reports

Fifth International Microgravity Combustion Workshop

This conference proceedings document is a compilation of 120 papers presented orally or as poster displays to the Fifth International Microgravity Combustion Workshop held in Cleveland, Ohio on May 18-20, 1999. The purpose of the workshop is to present and exchange research results from theoretical and experimental work in combustion science using the reduced-gravity environment as a research tool. The results are contributed by researchers funded by NASA throughout the United States at universities, industry and government research agencies, and by researchers from at least eight international partner countries that are also participating in the microgravity combustion science research discipline. These research results are intended for use by public and private sector organizations for academic purposes, for the development of technologies needed for the Human Exploration and Development of Space, and to improve Earth-bound combustion and fire-safety related technologies

Bibliography of Lewis Research Center technical publications announced in 1985

This compilation of abstracts describes and indexes the technical reporting that resulted from the scientific and engineering work performed and managed by the Lewis Research Center in 1985. All the publications were announced in the 1985 issues of STAR (Scientific and Technical Aerospace Reports) and/or IAA (International Aerospace Abstracts). Included are research reports, journal articles, conference presentations, patents and patent applications, and theses