1,720,973 research outputs found
Expansion tubes in Australia
No full textHypersonics research at the University of Queensland (UQ) was set in motion by the arrival of Professor Ray Stalker in 1977. Stalker, the inventor of the free-piston driver [1], soon commenced work on a large free-piston driven reflected shock tunnel (RST), the T4 facility, funded by the Australian Research Council [2]. This facility was a larger scale development of the earlier T1, T2, and T3 machines built at the Australian National University. T4 theoretically had sufficient scale to provide the test times, stagnation pressures, and to accommodate the model sizes, required to conduct hypersonic combustion and propulsion studies, and the facility became operational in 1987 [3]. While T4 was destined to become UQ’s workhorse for hypersonic flow experiments (T4 would fire its 10,000th shot in August 2008 [4]) around this same period, in the late 1980s, the new hypersonics group at UQ simultaneously began to investigate expansion tube operation. While RSTs dominated hypersonic ground testing in the 1980s and 1990s, it was always known that the stagnation of the test gas upstream of the supersonic nozzle limited them to sub-orbital flight speeds, and there remained the need for higher enthalpy ground testing capabilities
Simulating gas giant entry with increased helium diluent in an expansion tube
No full textThe Galileo probe’s 47.5 km/s entry into Jupiter on December 7th, 1995, was an engineering triumph. The probe survived entry into the atmosphere of the largest gas giant planet in the solar system, and completed its full scientific mission. However, analysis of the in-flight heat shield ablation by Milos [1] showed that ablation on both the stagnation point and the frustum of the sphere-cone heat shield differed from what the computational fluid dynamics (CFD) simulations and supporting experiments used to design it [2] had predicted. Stagnation point recession was over-predicted, and frustum recession was under-predicted. This disagreement between the predictions and the flight test data indicated that both experimental and simulated modelling of gas giant entry could be improved
Memories from My Entrance into the World of Shock Wave Phenomena as a PhD Student of Professor Glass and My Association with Him Thereafter
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Preliminary experimental investigation of air radiation in super-orbital expanding flow
No full textRadiative heating dominates forebody thermal loads on re-entry capsules travelling at superorbital speeds and has also recently been identified as a major component in afterbody heating. Although subjected to less severe heating, the afterbody heat shield is typically designed with a larger structural safety factor, limited by the fidelity of computational models used for the rapid flow expansion. To improve the understanding of afterbody flows, an experimental campaign was launched to interrogate the radiation from a rapidly expanding flow of 11.8 km/s air in the X2 expansion tunnel at the University of Queensland. Spectral measurements of the flow were successfully recorded from the ultraviolet to the near infrared, and two-dimensional images of atomic oxygen emission were also taken. The latter agreed well, in trend, with numerical simulations of the flow
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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