1,807 research outputs found
Self-sterilization of bodies during outer planet entry
A body encountering the atmosphere of an outer planet is subjected to heat loads which could result in high temperature conditions that render terrestrial organisms on or within the body nonviable. To determine whether an irregularly shaped entering body, consisting of several different materials, would be sterilized during inadvertent entry at high velocity, the thermal response of a typical outer planet spacecraft instrument was studied. The results indicate that the Teflon insulated cable and electronic circuit boards may not experience sterilizing temperatures during a Jupiter, Saturn, or Titan entry. Another conclusion of the study is that small plastic particles entering Saturn from outer space have wider survival corridors than do those at Jupiter
Unsteady aerodynamic theory for membrane wings
We study analytically the dynamic response of membrane aerofoils subject to
arbitrary, small-amplitude chord motions and transverse gusts in a
two-dimensional inviscid incompressible flow. The theoretical model assumes
linear deformations of an extensible membrane under constant tension, which are
coupled aeroelastically to external aerodynamic loads using unsteady thin
aerofoil theory. The structural and aerodynamic membrane responses are
investigated for harmonic heave oscillations, an instantaneous change in angle
of attack, sinusoidal transverse gusts, and a sharp-edged gust. The unsteady
lift responses for these scenarios produce aeroelastic extensions to the
Theodorsen, Wagner, Sears, and K\"{u}ssner functions, respectively, for a
membrane aerofoil. These extensions incorporate for the first time membrane
fluid-structure interaction into the expressions for the unsteady lift response
of a flexible aerofoil. Our results suggest that membrane aerofoils with
appropriately tuned pretension could possess substantial aerodynamic benefits
over rigid aerofoils in unsteady flow conditions.Comment: 35 pages, 39 figure
Performance of silicon solar cell assemblies
Solar cell assembly current-voltage characteristics, thermal-optical properties, and power performance were determined. Solar cell cover glass thermal radiation, optical properties, confidence limits, and temperature intensity effects on maximum power were discussed
Experimental investigation of heat transfer effectiveness on finned-tube thermoacoustic heat exchanger
Heat exchangers are some of the most important parts in thermoacoustic devices. In an oscillatory flow condition, the flow and temperature fields around the heat exchangers can be quite complex and it may significantly affect their heat transfer behaviour. As a result, one cannot directly apply the heat transfer correlations for a steady flow to the design of heat exchangers operating in oscillatory flow conditions. However, the fundamental knowledge of heat transfer in oscillatory flow is still not well established. The aim of the current work is to establish the heat transfer correlation for a few selected finned-tube heat exchangers, by measuring the heat transfer from the heat exchangers to the oscillatory flow in a range of operating conditions. Among the main parameters considered are fin spacing, fin length, thermal penetration depth, and gas displacement amplitude, and their effect on the thermal performance of heat exchangers. The results are presented in term of heat transfer effectiveness, which is the ratio of actual heat transfer rate to the maximum possible heat transfer rate. The correlations are proposed between the heat transfer effectiveness and the ratios of the fin length to the displacement amplitude and the fin spacing to the thermal penetration depth. The uncertainties associated with all the measurement data are also considered
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