(142ao) Detailed Simulations of Lagrangian Particle Transport in Turbulent Reacting Flows

An understanding of particle dynamics in turbulent flows is important to many biological, environmental and industrial fields. We are performing fundamental investigation into dispersive transport and time-temperature histories of Lagrangian particles in turbulent reacting flows. Of specific focus is the defeat of biological agents using explosively dispersed gas through thermal or chemical reaction. It is of great significance to predict the statistics of the interaction of biological aerosol with the reacting flow, particularly the full particle temperature probability density function (PDF). A great challenge in modeling of particle motions in computational fluid dynamics is the accurate prediction of fine-scale aerosol-fluid interactions. Direct numerical simulation (DNS) studies provide a detailed description of two-phase flows, but they are very expensive computationally, even at moderate Reynolds numbers and particle densities. Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) approaches are computationally efficient, but cannot resolve fine structures and require modeling of unknown subgrid statistics. A computationally affordable stochastic modeling approach, one-dimensional turbulence (ODT), is a proven method that captures the full range of length and time scales (in one-dimension), and provides detailed statistical information of fine-scale turbulent-particle mixing and transport. 

Limited results of particle transport in ODT have been previously reported in non-reacting flow. Here, we present the implementation and validation of a Lagrangian particle model into an existing reacting ODT code. Results of particle transport in three flow configurations--channel flow, homogeneous isotropic turbulence, and jet flames--are presented. The work investigates the functional dependence of the statistics of particle-flow interactions. A parametric study is performed varying temperature profiles, Reynolds numbers, and particle Stokes numbers. Particle temperature histories and PDFs are presented. The simulations also allow the analysis of time scale and the sensitivity of initial and boundary conditions, and other physical parameters. Flow statistics of the ODT particle model are compared to both experimental measurements and DNS data. The successful validation of Lagrangian particle transport in ODT has the potential for much more efficient investigation of fine-scale turbulence-particle interactions and access to a wider Reynolds number range than available using DNS.