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On focusing of strong shock waves
KTH, School of Engineering Sciences (SCI), Mechanics.
2005 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Focusing of strong shock waves in a gas-filled thin test section with various forms of the reflector boundary is investigated. The test section is mounted at the end of the horizontal co-axial shock tube. Two different methods to produce shock waves of various forms are implemented. In the first method the reflector boundary of the test section is exchangeable and four different reflectors are used: a circle, a smooth pentagon, a heptagon and an octagon. It is shown that the form of the converging shock wave is influenced both by the shape of the reflector boundary and by the nonlinear dynamic interaction between the shape of the shock and the propagation velocity of the shock front. Further, the reflected outgoing shock wave is affected by the shape of the reflector through the flow ahead of the shock front. In the second method cylindrical obstacles are placed in the test section at various positions and in various patterns, to create disturbances in the flow that will shape the shock wave. It is shown that it is possible to shape the shock wave in a desired way by means of obstacles. The influence of the supports of the inner body of the co-axial shock tube on the form of the shock is also investigated. A square shaped shock wave is observed close to the center of convergence for the circular and octagonal reflector boundaries but not in any other setups. This square-like shape is believed to be caused by the supports for the inner body. The production of light, as a result of shock convergence, has been preliminary investigated. Flashes of light have been observed during the focusing and reflection process.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , vi, 42 p.
Series
Trita-MEK, ISSN 0348-467X ; 2005:16
Keyword [en]
shock focusing, imploding shock, converging shock, reflected shock, annular shock tube
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-565ISBN: 91-7178-207-9 (print)OAI: oai:DiVA.org:kth-565DiVA: diva2:14447
Presentation
2005-12-15, S40, Teknikringen 8, Teknikringen 8, 10:15
Opponent
Supervisors
Note
QC 20101126Available from: 2005-12-20 Created: 2005-12-20 Last updated: 2011-09-07Bibliographically approved
List of papers
1. Focusing of strong shocks in an annular shock tube
Open this publication in new window or tab >>Focusing of strong shocks in an annular shock tube
2007 (English)In: Shock Waves, ISSN 0938-1287, E-ISSN 1432-2153, Vol. 15, no 3-4, 205-217 p.Article in journal (Refereed) Published
Abstract [en]

Focusing of strong shock waves in a gas-filled thin convergence chamber with various forms of the reflector boundary is investigated experimentally and numerically. The convergence chamber is mounted at the end of the horizontal co-axial shock tube. The construction of the convergence chamber allows the assembly of the outer chamber boundaries of various shapes. Boundaries with three different shapes have been used in the present investigation-a circle, an octagon and a smooth pentagon. The shock tube in the current study was able to produce annular shocks with the initial Mach number in the range M-s = 2.3-3.6. The influence of the shape of the boundary on the shape and properties of the converging and reflected shock waves in the chamber has then been investigated both experimentally and numerically. It was found that the form of the converging shock is initially governed by the shape of the reflector and the nonlinear interaction between the shape of the shock and velocity of shock propagation. Very close to the center of convergence the shock obtains a square-like form in case of a circular and octagonal reflector boundary. This is believed to stem from the instability of the converging shock front triggered by the disturbances in the flow field. The outgoing, reflected shocks were also observed to be influenced by the shape of the boundary through the flow ahead as created by the converging shocks.

Keyword
shock focusing, annular shock tube, converging shock, reflected shock, AUFS vector splitting scheme
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-7427 (URN)10.1007/s00193-006-0035-0 (DOI)000239249200005 ()2-s2.0-33746453712 (Scopus ID)
Note

QC 20141128

Available from: 2007-08-31 Created: 2007-08-31 Last updated: 2017-12-14Bibliographically approved
2. The Production of Converging Polygonal Shock Waves by Means of Reflectors and Cylindrical Obstacles
Open this publication in new window or tab >>The Production of Converging Polygonal Shock Waves by Means of Reflectors and Cylindrical Obstacles
2006 (English)In: Flow Dynamics / [ed] Tokuyama, M; Maruyama, S, 2006, Vol. 832, 445-449 p.Conference paper, Published paper (Refereed)
Abstract [en]

Converging and reflecting strong shock waves are investigated experimentally in a horizontal co-axial shock tube. The shock tube has a test section mounted at the end of the tube. Two different methods to produce various geometrical shapes of shock waves are tested. In the first method the reflector boundary of the test section is exchangeable and four different reflectors are used: a circle, a smooth pentagon, a heptagon and an octagon. It is shown that the form of the converging shock wave is influenced both by the shape of the reflector boundary and by the nonlinear dynamics between the shape of the shock and the velocity of the shock front. Further, the reflected outgoing shock wave is affected by the shape of the reflector through the flow ahead of the shock front. In the second method we use cylindrical obstacles, placed in the test section at various positions and patterns, to create disturbances in the flow that will shape the shock wave. It is shown that it is possible to shape the shock wave in a desired way with these obstacles. The influence of the supports of the inner body of the co-axial shock tube is also investigated. A square shaped shock wave is observed close to the center of convergence for the circular and octagonal reflectors but not in any other setups. This square-like shape is believed to be caused by the supports for the inner body.

Series
AIP CONFERENCE PROCEEDINGS, ISSN 0094-243X ; 832
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-7429 (URN)10.1063/1.2204539 (DOI)000237700400083 ()2-s2.0-33845448117 (Scopus ID)0-7354-0324-4 (ISBN)
Conference
2nd International Conference on Flow Dynamics Location: Sendai, JAPAN Date: NOV 16-18, 2005
Note
QC 20100707. Previous title: The production of strong converging shocksAvailable from: 2007-08-31 Created: 2007-08-31 Last updated: 2011-10-05Bibliographically approved
3. Controlling the form of strong converging shocks by means of disturbances.
Open this publication in new window or tab >>Controlling the form of strong converging shocks by means of disturbances.
2007 (English)In: Shock Waves, ISSN 0938-1287, E-ISSN 1432-2153, Vol. 17, no 1-2, 29-42 p.Article in journal (Refereed) Published
Abstract [en]

The influence of artificial disturbances on the behavior of strong converging cylindrical shocks is investigated experimentally and numerically. Ring-shaped shocks, generated in an annular cross sectional shock tube are transformed to converging cylindrical shocks in a thin cylindrical test section, mounted at the rear end of the shock tube. The converging cylindrical shocks are perturbed by small cylinders placed at different locations and in various patterns in the test section. Their influence on the shock convergence and reflection process is investigated. It is found that disturbances arranged in a symmetrical pattern will produce a symmetrical deformation of the converging shockfront. For example, a square formation produces a square-like shock and an octagon formation a shock with an octagonal front. This introduces an alternative way of tailoring the form of a converging shock, instead of using a specific form of a reflector boundary. The influence of disturbances arranged in non-symmetric patterns on the shape of the shockfront is also investigated.

Keyword
shock focusing; annular shock tube; imploding shock
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-7428 (URN)10.1007/s00193-007-0087-9 (DOI)000248819100003 ()2-s2.0-34547906425 (Scopus ID)
Note
QC 20100706 Tidigare titel: Controlling the form of strong converging shocks(20101126)Available from: 2007-08-31 Created: 2007-08-31 Last updated: 2017-12-14Bibliographically approved

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Citation style
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