Session F25: Multiphase Flows: Compressible Multiphase Flows

Simulation of detonation-driven particle motion employing the compressible MRG force model -- comparison against microscale experiments

Recent work in the high-speed, multiphase flow community has demonstrated the predictive aptitude of the compressible Maxey-Riley-Gatignol (C-MRG) force model for problems of shock-particle interaction. High-quality data from an explosive, multiphase flow experiment permits an exploration of the model’s accuracy in the detonation-driven flow regime. Calibrated explosive model parameters from a UQ-driven flow study afford a time-dependent simulation flow field that agrees with experimental measurements. Finite-volume, Euler-Lagrange simulations employing the Faxén form of the particle force model are performed, where spatial and temporal variations of flow properties on the scale of the particle are considered. The explosion-induced motion of a few tungsten particles is captured by precisely timed X-ray exposures, and compared with simulation results for evaluation of the accuracy of the force model.   

Assessment of low-speed mixing and diffusion models for detonating compressible turbulence

The motivation for the present study is the relevance to supersonic spray combustion, such as in scramjet engines where the fuels are used in the liquid state. The evaluation of various drag, heat, and mass transfer models for two-phase high-speed flows is undertaken in this study. Several models for hydrodynamic drag coefficient in high-speed flows are introduced and four nonlinear first order differential equations appropriate for supersonic flows that carry particles are numerically solved to examine the comparative effects of the drag models. A preliminary study on a constant-area nozzle shows the differences in the performance of the drag models as a function of the Reynolds number and the Mach number. The particle velocity, time-of-flight of the particle, and the variation of the flow variables along the nozzle will be reported. The drag models give comparable results for some quantities, except one model which shows a significantly different result for intermediate Mach numbers (1.0 ≤ Ma ≤ 1.7).   

Unsteady Compressible Pairwaise Interaction Extended Point-Particle model

An efficient means to compute multiphase flow problems is to utilize the Euler-Lagrange simulation method. Various developments have been made for the case in the incompressible regime using the pairwise interaction extended point-particle (PIEP) model. The current work extends the PIEP model to cope with the unsteady nature of compressible multiphase flows. A framework is developed using acoustic wave solution and compressible Maxey-Riley-Gatignol equation to predict unsteady secondary forces on a sphere under the influence of a scattering sphere nearby. A case with two spheres while a weak shock passes through is studied. The model is capable of capturing the arrival timing of the scattered signal. Comparisons are made with the force prediction from a particle resolved 2-sphere unsteady simulation.   

Evaporation and Break-up effect in a Shock Driven Multiphase Instability

 

New experimental equipment, methodologists and techniques are utilized on the investigation of the impulsive acceleration of a heterogeneous multiphase flow-field within a shock tube system. A remodel diaphragm loader was built to withstand higher shocks speed and a new equipment was designed to create an uniform curtain (2 in x 0.5 in) multiphase interface. The interface mixture is compressing of nitrogen (carrier gas), and micro-sized acetone droplet, generated inside the shock tube’s test section. Nitrogen gas is pre-saturated with acetone vapor prior entering the test section. Acetone vapor will trace the interface morphology and prevent premature evaporation of the particle droplets. Droplets size and distribution are validated utilizing a Phase Doppler Particle Analyzer (PDPA). The multiphase interface is then impulsively accelerated by a planar shock wave. The development of the interface was captured through a series of Planar Laser Mie Scattering and Planar Laser-Induced Fluorescence images, respectively. Results of these experiments were compared against evaporation measurements with models like the D-Square-Law, breakup and simulations. Importantly, this study has a multitude of applications in multiple scientific and engineering systems; with significance importance on high-speed or shock-induced multiphase combustion.   

A pressure-based diffuse-interface method for two-phase flows with mass transfer

We present a pressure-based method for the numerical solution of a four-equation two-phase compressible flow model with mass transfer. The model assumes kinetic, mechanical and thermal equilibrium and it is composed of the equations for the volume fraction, temperature, velocity and pressure. It includes the effects of viscosity, surface tension, thermal conductivity and gravity. Mass transfer is modeled through a Gibbs free energy relaxation term. A key feature of the proposed pressure-based methodology for the model system solution is the use of high performance and scalable solvers for the solution of the Helmholtz equation for the pressure, which drastically reduces the computational cost. Several numerical  tests are presented to demonstrate the effectiveness of the proposed method,  including tests involving flows with large density ratios, flows at low  Mach number, and a challenging three-dimensional nucleate boiling simulation.