Nonlinear reflection of a spherically divergent N-wave from a plane surface: Optical interferometry measurements in air

Journal Article · Wed Oct 28 00:00:00 EDT 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4934477· OSTI ID:22492655

Yuldashev, P.; Khokhlova, V. ^[1]; Ollivier, S.; Blanc-Benon, Ph. ^[2]

---

1. Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation)
2. Laboratoire de Mécanique des Fluides et d’Acoustique, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully (France)

Mach stem is a well-known structure typically observed in the process of strong (acoustic Mach numbers greater than 0.4) step-shock waves reflection from a rigid boundary. However, this phenomenon has been much less studied for weak shocks in nonlinear acoustic fields where Mach numbers are in the range from 0.001 to 0.01 and pressure waveforms have more complicated waveforms than step shocks. The goal of this work was to demonstrate experimentally how nonlinear reflection occurs in air for very weak spherically divergent acoustic spark-generated pulses resembling an N-wave. Measurements of reflection patterns were performed using a Mach-Zehnder interferometer. A thin laser beam with sub-millimeter cross-section was used to obtain the time resolution of 0.4 µs, which is 6 times higher than the time resolution of the condenser microphones. Pressure waveforms were reconstructed using the inverse Abel transform applied to the phase of the signal measured by the interferometer. The Mach stem formation was observed experimentally as a result of collision of the incident and reflected shock pulses. It was shown that irregular reflection of the pulse occurred in a dynamic way and the length of the Mach stem increased linearly while the pulse propagated along the surface. Since the front shock of the spark-generated pulse was steeper than the rear shock, irregular type of reflection was observed only for the front shock of the pulse while the rear shock reflection occurred in a regular regime.

• OSTI ID: 22492655
• Journal Information: AIP Conference Proceedings, Vol. 1685, Issue 1; Conference: 20. international symposium on nonlinear acoustics, Ecully (France), 29 Jun - 3 Jul 2015, 2. international sonic boom forum, Ecully (France), 29 Jun - 3 Jul 2015; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
42 ENGINEERING
AIR
CROSS SECTIONS
HEAT EXCHANGERS
INTERFEROMETRY
LASER RADIATION
LENGTH
MACH-ZEHNDER INTERFEROMETER
NONLINEAR PROBLEMS
PULSES
REFLECTION
SHOCK WAVES
SIGNALS
SOUND WAVES
SPHERICAL CONFIGURATION
SURFACES
TIME RESOLUTION
VAPOR CONDENSERS
WAVE FORMS