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Energy concentration by spherical converging shocks generated in a shock tube
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.
KTH, School of Engineering Sciences (SCI), Mechanics.
2012 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 24, no 12, 126103- p.Article in journal (Refereed) Published
Abstract [en]

Spherical converging shock waves are produced in a conventional shock tube with a circular cross-section. Initially, plane shocks are transformed into the shape of a spherical cap by means of a smoothly convergent cross-section. The wall shape in the transformation section is designed to gradually change the form of the shock wave until it approaches a spherical shape. Thereafter, the shock enters a conical section where it converges towards the apex of the cone. Numerical calculations with the axisymmetric Euler equations show that the spherical form is only slightly dependent on the initial Mach number of the plane shock within the range 1.5 < MS < 5.5, and is preserved to a close vicinity of the focal point. The test gas is heated to very high temperatures as a result of shock convergence and emits a bright light pulse at the tip of the test section. The light radiation is collected by optical fibers mounted at the tip of the convergence chamber and investigated by photometric and spectroscopic measurements. Experiments are performed with argon and nitrogen and with different initial Mach numbers. The radiation of the shock-heated argon closely resembles blackbody radiation. Fits to the experimental data result in apparent blackbody temperatures in argon of up to ~27 000 K, some 250 ns after the focusing instant. The initial Mach number in these spectrometric runs is MS = 3.9, indicating an efficient amplification of the shock wave strength.

Place, publisher, year, edition, pages
2012. Vol. 24, no 12, 126103- p.
Keyword [en]
Axisymmetric, Black body radiation, Blackbody temperatures, Circular cross-sections, Converging shock waves, Energy concentration, Focal points, High temperature, Light pulse, Light radiation, Numerical calculation, Spectroscopic measurements, Spherical shape, Test gas, Test sections, Wave strengths
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URN: urn:nbn:se:kth:diva-116788DOI: 10.1063/1.4772073ISI: 000312833500039ScopusID: 2-s2.0-84871871140OAI: diva2:600928
Swedish Research Council

QC 20130128

Available from: 2013-01-28 Created: 2013-01-28 Last updated: 2013-02-01Bibliographically approved

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