Ali Ozel

Towards filtered drag force model for non-cohesive and cohesive particle-gas flows

Euler-Lagrange simulations of gas-solid flows in unbounded domains have been performed to study sub-grid modeling of the filtered drag force for non-cohesive and cohesive particles. The filtered drag forces under various microstructures and flow conditions were analyzed in terms of various sub-grid quantities: the sub-grid drift velocity, which stems from the sub-grid correlation between the local fluid velocity and the local particle volume fraction, and the scalar variance of solid volume fraction, which is a measure to identify the degree of local inhomogeneity of volume fraction within a filter volume. The results show that the drift velocity and the scalar variance exert systematic effects on the filtered drag force. Effects of particle and domain sizes, gravitational accelerations, and mass loadings on the filtered drag are also studied, and it is shown that these effects can be captured by both sub-grid quantities. Additionally, the effect of cohesion force through the van der Waals interaction on ...

Intrusion of a Liquid Droplet into a Powder under Gravity

Intrusion of a liquid droplet into a hexagonal close-packed array of spheres under gravity is investigated using analytical methods and volume-of-fluid simulations. Four regimes of ultimate fluid behavior are identified: (A) no liquid imbibition into the bed, (B) trapping of liquid high in the bed, (C) liquid descending to the bottom of the bed, and (D) liquid spreading around the surface of all particles. These regimes are mapped based on the contact angle and Bond number of the system. Many aspects of the dynamics and ultimate liquid behavior are captured using a simplified model of a mass of liquid moving under gravity in a vertical capillary of undulating cross-sectional area. This simplified model is used to form momentum transport equations with four forms of nondimensional time, which are shown to collapse the simulation data with different fluid parameters in different regimes.

Toward Constitutive Models for Momentum, Species, and Energy Transport in Gas–Particle Flows

As multiscale structures are inherent in multiphase flows, constitutive models employed in conjunction with transport equations for momentum, species, and energy are scale dependent. We suggest that this scale dependency can be better quantified through deep learning techniques and formulation of transport equations for additional quantities such as drift velocity and analogies for species, energy, and momentum transfer. How one should incorporate interparticle forces, which arise through van der Waals interaction, dynamic liquid bridges between wet particles, and tribocharging, in multiscale models warrants further study. Development of multiscale models that account for all the known interactions would improve confidence in the use of simulations to explore design options, decrease the number of pilot-scale experiments, and accelerate commercialization of new technologies.