Dispersion of hydrogen releases from a liquid surface and surface bursting behaviour

• We consider hydrogen dispersion from bursting bubbles on a water surface.
• Z type schlieren system is used to visualise releases from small bubbles.
• Lens and grid system is used to visualise releases up to 22 L.
• Following hole nucleation the rim rapidly retracts and hydrogen is forcefully ejected.
• Extent of flammable atmosphere found proportional to V1/3 for small bubble bursts.

The release and dispersion of hydrogen at a liquid surface has been studied experimentally for hydrogen releases from single bursting bubbles of a few cm3 in volume to larger scale releases of up to 22 L. The investigation of single bubble bursting and dispersion was undertaken using high speed video to record the bubble burst in conjunction with a high speed schlieren video system to visualise the hydrogen dispersion. Following the nucleation of a hole, surface tension causes the liquid film to peel back rapidly forming a ring/torus of liquid around the enlarging hole. This process is similar to that with air bubbles and lasts only a few milliseconds. The resulting plume can then be seen to disperse over a timescale of a few hundred ms. To visualise the dispersion of the larger releases, a lens and grid schlieren system was employed to obtain a much larger field of view. The larger releases tend to start to breakup before reaching the surface. The schlieren images for the large release show that the release does not emerge as a single coherent volume and the complex mixing/turbulence induced following bubble bursting and breakup of the release can be readily seen.