Investigation of the Richtmyer-Meshkov instability using digital holography in the context of catastrophic aerobreakup

We perform shock tube experiments with high-speed digital holography to investigate Richtmyer-Meshkov instabilities on an air-sulfur hexafluoride gaseous interface and understand the formation of windward surface waves in catastrophic hydrometeor aerobreakup. The catastrophic aerobreakup phenomenon is described by an extremely abrupt disintegration of the drop mass upon impulsive acceleration, the existence of which is still a matter of debate in the scientific community as little relevant evidence is available for support and the shock strengths needed are typically very high (Mach numbers >= 6), posing safety concerns, experimental complexities and higher operation costs. A gaseous interface created with a bubble film herein requires a much lower shock strength (Mach 1.2) to form similar windward instabilities providing an opportunity to obtain high resolution data in much simpler and safer laboratory tests. In addition, the use of digital holography allows the captured wavefront to be reconstructed at different depths and determine the three-dimensional location and shape of the bubble interface with greater precision than otherwise afforded by two-dimensional imaging. Our results reveal an exponential growth for RM instabilities on the gaseous bubble interface immediately after shock passage that shows excellent agreement with the linearized Rayliegh-Taylor theory and closely resembles the windward unstable waves observed by past studies in the catastrophic hydrometeor aerobreakup. The growth rates can be varied by modulating the pre-shock interfacial perturbation and provide a possible pathway in future to control catastrophic aerobreakup times that can be of importance to many hypersonic flight related problems due to adverse weather conditions.

Automated summary

We conducted shock tube experiments with high-speed digital holography to study the Richtmyer-Meshkov instabilities on an air-sulfur hexafluoride gaseous interface and better understand the formation of windward surface waves during catastrophic hydrometeor aerobreakup. By using a gaseous interface created with a bubble film, we achieved similar instability patterns with much lower shock strength, allowing for simpler and safer laboratory tests with high resolution data. Our findings suggest potential applications in controlling catastrophic aerobreakup in hypersonic flight under adverse weather conditions.