At low gas densities the standard optical techniques for visualization of compressible gas flows become insensitive. For models in hypersonic shock or wind tunnels this limitation generally restricts the use of visualization tech-Visualization Technique niques to shock position measurements; particularly when three-dimensional flow fields are being investigated.for Low-Density The initial development of a quantitative low-density visualization technique is discussed in this paper. The Flow Fields method is based on the electron beam fluorescence probe and operates as follows. Any desired plane section of a one-, two-, or three-dimensional flow field is selected for BERNADETTE L. MAGUIRE, Member, IEEE study. An electron beam is oscillated in this plane. The E. PHILLIP MUNTZ resulting sheet or curtain of fluorescence, which has a JOHN R. MALLIN, Member, IEEE thickness of one beam diameter, has an intensity dis-General Electric Company tribution proportional to the gas density and electron Space Sciences Laboratory beam current distribution in the plane. King of Prussia, Penn.If a photograph is taken of the fluorescence, the film records the intensity distribution in the plane defined by the oscillating beam. Thus, if the film is calibrated and the current distribution known, quantitative information about the density distribution in the plane is available. AbstractIn order to photograph the relatively low intensity A quantitative visualization technique based on an electron beam fluorescence in a short time, such as is typical of a shock fluorescence probe has been investigated for low-density flow fields. tunnel run, it is necessary to use an image intensifier sys-The design considerations and operating range of the instrumentation tem rather than merely a camera. The complete visualizasystem are described. Initial data on the visualization of the flow field tion system is illustrated in Fig.
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