Using ejecta measurement simulations to predict real-life results

Subjecting a metal to a severe impact can produce a cloud of small, fast particles, called ejecta. Studying ejecta and the size-velocity distribution of these particles offers valuable insight into matter’s properties at rest, along with information related to the forces and effects of collisions in many applications, such as geological history, crater formation, and disaster preparedness.

Mie-scattering and holography diagnostics have offered insights into particle size-velocity distribution after impact. However, these methods are difficult to use and unable to analyze complex ejecta formation.

Don Jayamanne et al. investigated the use of Photon Doppler Velocimetry (PDV) simulations to obtain additional information on ejecta in real-life situations.

“Because of their extreme velocity, ejecta phenomena are brief and hard to characterize,” said author Jérôme A. Don Jayamanne. “Since light is much faster than these particles, it can be sent into the ejecta during this short time. By analyzing the portion of light that comes back, we can deduce more characteristics of the ejecta.”

The team used simulated PDV spectrograms to predict an ejecta’s size distribution through different media. To determine the translation of these results to experimental situations, tin disks engraved with surface grooves were placed into a gas-filled tube and shocked by a copper flyer traveling at 1650 m/s. The ejecta size and velocity distribution results were used to verify drag forces and particle breakup in helium and air. Better projection of the initial size distribution of the ejecta was achieved by matching the simulated spectrograms to the experimental results.

“This work is a new way of analyzing ejection data by bringing new physics to existing simulation frameworks,” said Don Jayamanne.

Source: “Recovering particle velocity and size distributions in ejecta with photon Doppler velocimetry,” by J. A. Don Jayamanne, R. Outerovitch, F. Ballanger, J. Bénier, E. Blanco, C. Chauvin, P. Hereil, J. Tailleur, O. Durand, R. Pierrat, R. Carminati, A. Hervouët, P. Gandeboeuf, and J. R. Burie, Journal of Applied Physics (2024). This article can be accessed at https://doi.org/10.1063/5.0220642 .