Session A06: Particle-laden Flows: Compressible

Investigation of Explosive Particle Jetting Phenomena at the Mesoscale

It is known that particle jetting occurs from the explosive dispersal of particles, but it is still not completely understood what the driving mechanisms may be. A numerical investigation is undertaken to explore the particle jetting phenomenon. Multiphase simulations are conducted at the mesoscale of a cloud of fully-resolved particles. Kinematic quantities of each individual particle are resolved directly, allowing for tracking of particle and fluid phase interactions. The parallel adaptive wavelet-collocation method (PAWCM) is used to perform the simulations with high numerical accuracy at relatively low computational cost. Methods by which particle jets may form are explored by imposing initial conditions such as spatial perturbations in particle volume fraction and variations in particle elasticity, along with variations in the type, strength, and duration of wave loading. Statistical analysis is performed to establish a quantitative definition for a particle jet, which is then used to determine how different parameters impact formation and prominence. This work sheds light on the potential underlying mechanisms of particle jetting phenomena and may further inform macro-scale particle models and complex multi-physics models. LA-UR-21-27365   

Interaction of inertial particles with eddy shocklets in high-speed turbulence

Turbulent flows at high Mach number are characterized by the emergence of eddy shock waves, which significantly change the divergence of the velocity field and the balance of kinetic energy. In several applications, such as solid-fuel scramjets, cold spray guns, protoplanetary disks, or volcanic eruptions, these flows carry a particulate phase which additionally releases or absorbs kinetic energy. However, while the understanding and modeling of incompressible or weakly compresssible particle-laden turbulence has seen significant progress in recent years, the interaction of particles with highly-compressible turbulence is hardly understood.

Particle-resolved simulations of compressible gas-particle flows at finite Mach number and volume fraction

In this work, we present particle resolved numerical simulations of homogeneous fluidization of monodispere rigid spheres. Simulations span a large range of Mach numbers and volume fractions to guide the development of subgrid scale models that can be employed in Euler-Euler and Euler-Lagrange methods. We assess the budget of pseudo-turbulent kinetic energy (PTKE), which includes drag production, viscous dissipation, and pressure strain. The role of gas-phase compressibility and neighbor-induced velocity fluctuations on the distribution of drag forces is also quantified. The present simulations are designed to provide new Mach number- and volume fraction-dependent correlations for drag and PTKE.   

Particle-resolved simulations of shock-induced size segregation

Shock-induced particle-laden flow is observed in a multitude of natural and engineering applications and is often polydisperse. This study investigates the flow phenomena of shock-induced size segregation and dispersion of bidisperse particles using particle-resolved direct numerical simulations. We evaluate a simple model that provides a fundamental understanding of the essential forces that contribute to particle dynamics. In addition, we evaluate the ability of existing models to capture particle dispersion and size segregation within an Eulerian-Lagrangian framework.   

Investigation of Shock-Induced Force Variations within a Random Distribution of Particles

Particle-resolved inviscid simulations of a random bed of particles interacting with an underwater planar shock are performed to quantify the specific impact neighboring particles have on variations of drag and impulse. The simulations are governed by the Euler equations with a non-ideal stiffened-gas equation of state describing the water. Various Mach numbers and volume fraction scenarios were studied. Although the average drag on the particle bed is similar to the isolated particle case, significant variations in force on individual particles were observed. The specific arrangement of neighbors leads to variations in the peak drag force and the impulse shows that for the entire duration of the simulation particles can experience a consistent force due to the pressure fields induced by surrounding particles. Finally, it was determined that the lateral force on a particle is the same order of magnitude as the streamwise force on the particle. This research will aid future simulations understand the influence of neighboring particles, and isolated force models must be altered for a random distribution of particles.   

Comparisons of Explosive Dispersal in Static, Supersonic, and High-Speed Conditions

Explosive dispersal is a challenging and rich topic of research in the multiphase flow community. Interesting questions arise when considering environments such as supersonic and hypersonic regimes. We simulate a dilute explosive dispersal in static, Mach 3 and 6 ambient conditions using an Eulerian-Lagrangian finite volume code. The explosive dispersal is simulated in an axisymmetric barrel with an exit into ambient conditions. A reactive burn model was used prior as the initial conditions of the explosive with the dilute particle bed in between the explosive and the barrel exit. For the non-static conditions, a bow shock is allowed to form over the barrel before the explosive is released.  Three virtual probe plates are simulated in three different locations downstream of the barrel exit to capture flow metrics. These plates capture the incipient flow properties at various times throughout the simulation.   

Numerical simulations of an underexpand jet impinging on a granular bed

The interactions between rocket exhaust plumes and the surface of extraterrestrial bodies during spacecraft landings involve complex multiphase flow dynamics that pose significant risk to space exploration missions. The two-phase flow associated with plume-surface interactions (PSI) is characterized by high Reynolds number transonic conditions with particle concentrations ranging from dilute to close-packing. In this talk, an Eulerian-Lagrangian framework for simulating gas-solid compressible flows under conditions relevant to PSI is presented. Simulations of underexpanded jets impinging on granular surfaces are performed to elucidate the role of nozzle pressure ratio on crater morphology, and quantify two-phase statistics during the erosion process.   

Kinetic-Based Model for Fully Compressible Polydisperse Gas-Particle Flows

Eulerian-Eulerian hyperbolic conservation equations for fully compressible, polydisperse, gas-particle flows are presented.  First, a kinetic-based model is developed for the polydisperse particle phase that accounts for collisional and frictional terms between spherical particles of different sizes. Then, the particle-phase model is formulated in terms of the moments of the particle size distribution, and particle velocity moments conditioned on the particle mass.  Transport equations for particle velocity moments up to fourth order are closed using the hyperbolic quadrature method of moments (HyQMOM). In the numerical implementation, the particle mass distribution is treated using quadrature-based moment methods wherein velocity moments conditioned on particle size are found with the conditional quadrature method of moments (CQMOM). The 1-D hyperbolic conservation equations for the gas and particle phases are solved using HLL numerical fluxes, and the coupling terms are treated using operator splitting to guarantee realizability of the moments. The ability of the proposed model to capture 1-D shocks interacting with dense, polydisperse, particle curtains, leading to particle size segregation, is demonstrated using numerical simulations.   

Improvements to a simple reacting hydride particle model

Ejecta particles form after a shock wave impacts a metal plate with a known roughness or prescribed surface perturbation. If these particles are ejected into a non-inert gas, exothermic reactions may occur and raise the temperature of the particle. Previous work developed a simple model for cerium ejecta particles with many limiting assumptions. Improvements to the model have been made to include full two-way momentum, mass, and energy coupling between the two phases along with a variable outer diameter. The results change slightly, but overall confirm the limiting assumptions originally used during development. Additional considerations for numerical stability are implemented to increase the overall robustness of the model. Approved for unlimited release: LA-UR-21-27383.