Christian C. Milioli

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 ...

On the statistical steady state gas-solid flow in a riser as predicted through a two-fluid simulation

This work is concerned with the extremely high computational costs of the two-fluid simulations of gas-solid flows in risers. In a previous article [1] a procedure was proposed to speed up the simulations towards the desired statistical steady state flow regime. In this continuing article the concern is turned to the time extent that a simulation must advance inside the statistical steady state regime so that suitable time averaged predictions can be made. An analysis is carried out using the results of a transient two-fluid simulation of a riser flow performed inside the statistical steady state regime. Time averaged results were produced considering different time averaging intervals of 5, 10, 15 and 20 seconds. Both the transient behavior of the predictions and the time averaged results are discussed. For the present case, it was found that 10 seconds of fluidization taken inside the statistical steady state regime are enough for a reasonable qualitative description of the average flow.