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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - NANOSHOCK (Manufacturing Shock Interactions for Innovative Nanoscale Processes)

Teaser

Summary

Within the project â€œNanoshock â€“ Manufacturing Shock Interactions for Innovative Nanoscale Processesâ€, we want to investigate the potential of shockwaves for in situ control of fluid processes with surgical precision. Shockwaves are discontinuities in the macroscopic fluid state that can lead to extreme temperatures, pressures and concentrations of energy. Applications of such shock interactions range from kidney-stone lithotripsy and drug delivery to advanced aircraft design. With the use of properly focused shockwaves on tissue material, e.g. , lesions with unprecedented surgical precision can be generated. Alternatively, improving combustion by enhanced mixing of fuels, shockwave interactions can help to further destabilize and atomize spray droplets. Our overall objective is to understand and predict the formation and control of shocks in complex environments such as living organisms using computational methods. The fundamental knowledge of shock generation and its dynamics is essential to unravel the path to technical solutions and leveraging the enormous potential of manufactured shocks in situ. For this purpose, we develop advanced numerical tools that have the capability to simulate accurately multi-physics problems of compressible fluid dynamics giving access to breakthrough innovations and high-impact technologies, ranging from shock-driven nanoparticle reactors to non-invasive shock-mediated low-impact cancer therapies.

Work performed

During the first period of the research project, we spent most efforts in developing an advanced multi-resolution solver for large-scale simulations with best-in-class numerical methods including low-dissipative shock-capturing (WENO schemes) and advanced level-set interface tracking with conservative interface interactions. Using MPI communication, our code framework is designed for large-scale simulations on modern high-performance architectures such as the SuperMUC at the Leibniz-Rechen-Zentrum in Garching.

The computational cost of numerical fluid simulations is determined by the necessary spatial resolution of the smallest relevant flow structures and, concurrently, by the large amount of time-integration steps due to small time-increments. To improve the performance of the algorithm we have developed an adaptive local time-stepping scheme that ensures stability of the method at maximum possible time-step sizes.

In a first attempt to model cavitation effects in organisms, we have studied the bubble collapse near a gelatin interface using fluid material models. A quantification of pressure peaks and the so-called reentrant-jet into the gelatin phase shows the dependence of the gelatin penetration with the initial bubble configuration. This simplified setup serves as generic model to study the perforation of living cells, as it occurs e.g. during sonoporation (transient increase of cell permeability with improved drug uptake).

A very different process is shock-driven nanoparticle generation by laser ablation, yet the underlying physical mechanisms are very similar to shock-bubble interactions. The very localized deposition of high energies in liquids can generate vapor bubbles that eventually collapse and emit shockwaves. We have extended our level-set method for this effect to mimick the laser-induced cavity formation and simulated a so-called liquid drop explosion. Our results show very detailed insight of the cavity formation and agree well with a very recent experiment.

Up to now, the scientific results of our work are published in a journal publication (Diegelmann et al., Combustion and Flame, 174:85-99, 2016) and one technical report (Adami et al., Proc. of the 2016 Summer Progam, CTR, Stanford University, 2016). Additionally, we have presented our work to the scientific community at various conferences.

Final results

Our advanced numerical methods allow for very detailed direct numerical simulations of compressible interface mechanisms at unprecedented accuracy. The fully MPI-parallelized code environment enables large scale (space and/or time) simulations to investigate realistic physical problems. Within the next project period, we will make the simulation environment publically available under an open-source license. Ideally, other researchers can use this code and participate in the development to improve future simulation capabilities.

Our mission is to offer tools that help to understand and improve medical treatments and other applications based on cavitation effects.

Our vision are new strategies for improved medical therapies â€“ both in terms of micro-surgery to destroy malign tissue as well as enhancing efficacy of medical drugs.