Interaction of weak shocks leading to Mach stem formation in focused beams and reflections from a rigid surface: numerical modeling and experiment

Maria Karzova , Edouard Salze (1) , Sébastien Ollivier , Thomas Castelain (1) , Benoît André (1) , Petr Yuldashev (1) , Vera Khokhlova (2) , Oleg Sapozhnikov , Philippe Blanc-Benon (1)

1 LMFA - Laboratoire de Mecanique des Fluides et d'Acoustique
2 Department of Acoustics, MSU

Mach stem is a well-known structure observed in the process of interaction of two strong shock waves (Mach number M_a > 0.1), typically in the case of reflections from a rigid boundary. However this phenomenon has not been studied in detail for weak shocks in nonlinear acoustic fields, i.e. for acoustic Mach number in the range from 10^-3 to 10^-2. In acoustics, interaction of shocks occurs in the case of reflections or in the focusing of high power nonlinear beams. The goal of this paper is to investigate this phenomenon in a field of weak shocks both numerically and experimentally. The KZK nonlinear evolution equation was used to show the formation of the Mach stem in the focal region of the periodic and pulsed beams for the Mach number of about 10^-3. Experiments were performed in air using spark-generated N-waves reflecting from a rigid boundary. Shock fronts were visualized using Schlieren method. Regular and irregular reflections were observed experimentally and corresponding values of critical parameters for either type of reflection to occur were determined. This work is supported by the French/Russian International Program for Scientific Cooperation PICS (RFBR 10-02-91062/CNRS 5063).

Mots clés: Mach stem; irregular reflection

Domaines: Acoustique [physics.class-ph]

Maria Karzova, Edouard Salze, Sébastien Ollivier, Thomas Castelain, Benoît André, et al.. Interaction of weak shocks leading to Mach stem formation in focused beams and reflections from a rigid surface: numerical modeling and experiment. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811290⟩