Numerical analysis of particle-turbulence interaction in high-speed gas flows

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The interaction of high-speed gas flows with dispersed solid particles or droplets plays a decisive role in various geophysical, astrophysical, and technical processes. Examples include explosive volcanic eruptions, the formation of supernovae, cold spraying to deposit surface coatings, and supersonic combustion engines. These multiphase systems are characterized by a complex interplay of gas-phase turbulence, particle dynamics, heat transfer, and compressibility effects such as shock waves. Despite the large variety of applications, the fundamental mechanisms of particle-turbulence interaction in these flows are still poorly understood. The large number of involved physical effects and the vast range of different length and time scales exacerbate numerical analyses of these systems. Similarly, these conditions often prevent detailed experimental measurements. The lack of fundamental understanding inhibits the development of particle and turbulence models; however, accurate models are indispensable for predictive simulations in the above mentioned applications. As an example, the impact of explosive volcanic eruptions on the nearby population, aviation, and global climate is barely predictable due to the current lack of models describing the interaction of gas, magma, and rock fragments at very high velocities.In this project, novel highly-resolved numerical analyses of particle-turbulence interaction in the presence of pronounced compressibility effects and heat transfer will be conducted to enable model development and validation. The canonical flow problem of isotropic turbulence is considered which facilitates to gain understanding of the fundamental mechanisms which determine the multiphase interaction. Using an efficient numerical method recently developed by the applicant, the turbulent motion and the flow field around each particle will be fully resolved via the physical conservation laws. This approach yields an accurate description of the multiphase interaction which has not been documented for this class of flows previously. The data will provide new insight into the mutual influence of particles and compressible turbulence, e.g., detailing the momentum and energy balances of both phases. By comparison with these reference solutions, the accuracy of existing, yet never validated particle models will be analyzed. Furthermore, based on the gained knowledge and mechanistic approaches, new models will be developed. The thorough definition of the models and their range of validity is crucial for the accuracy of applied simulations.