What question did this study set out to answer?

This study aims to investigate the interaction between converging shock waves and a cylindrical air bubble in a gel-water solution.

April 22, 2026Open Access

Synchrotron radiography of wire-driven cylindrically converging shock waves interacting with a cylindrical bubble

FGF. GarciaKTH Royal Institute of Technology SBSourabh BhardwajKTH Royal Institute of Technology SMSebastián Rojas Mata

Key Points

This study aims to investigate the interaction between converging shock waves and a cylindrical air bubble in a gel-water solution.
Experimental study using wire-driven shock waves generated by a high-voltage system.
Numerical hydrodynamic simulations with a compressible multiphase Navier–Stokes solver.
X-ray radiography at a pulse rate of 5.68 MHz with synchronized high-speed cameras.
The experiments show Richtmyer–Meshkov instability in bubble collapse.
In the cylindrical configuration, predictions indicate Mach 14.1 at the focus of the shock wave.
The semicylindrical configuration produces a supersonic jet at 885 ± 30 m/s, leading to high-pressure regions and complex flow dynamics.

Abstract

The interaction between cylindrically converging shock waves (SWs) in a water–gelatine solution and a coaxial cylindrical air bubble is studied experimentally and numerically. Two configurations are considered: (i) an azimuthally symmetric, cylindrically converging SW of Mach 1. 35 impinging on a coaxial cylindrical bubble, and (ii) a semicylindrical converging SW of Mach 1. 45 (corresponding to half of the cylindrical front), interacting with the same target. Shock waves are generated by exploding wire arrays driven by a high-voltage pulsed power system at beamline ID19 of the European Synchrotron Radiation Facility, delivering currents up to 130\, kA with rise times of 0. 35 and 0. 55\, x03BC s to the cylindrical and semicylindrical wire loads, respectively. X-ray radiography is conducted at a pulse repetition rate of 5. 68 MHz using two synchronised high-speed cameras. Numerical hydrodynamic simulations are performed using a compressible multiphase Navier–Stokes solver. A Gilmore-type model for compressible cylindrical bubble pulsation provides an independent analytical estimate of the interface evolution. In the cylindrical SW configuration, the bubble collapse in experiments exhibits Richtmyer–Meshkov instability spikes. The cylindrically converging shock is analysed with Guderley’s solution and Whitham’s approximation using a real-gas equation of state, predicting Mach 14. 1 near the focus. In the semicylindrical configuration, momentum focuses into a single supersonic jet with a speed of 885 30 m s −1, producing localised high-pressure regions, coherent vortices and complex internal Mach reflections. Experiments, simulations and theory are consistent in collapse time, interface motion and overall flow dynamics.

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