Experimental investigation and CFD modeling of interstitial fluid effect in fluid -particle flow with particle -particle collisions
Abstract
A new two-fluid model, which employs kinetic theory of dense gas concepts to describe momentum and kinetic energy transfer between colliding particles, has been developed to simulate dilute turbulent fluid-particle flows with particle-particle collisions. The present model incorporates the influence of the interstitial fluid on the random motion of the particles by introducing two distinct particle coefficients of restitutions ef and es to characterize the inelasticity of particles colliding in a fluid and in a vacuum, respectively. Unlike other existing two-fluid flow models, which are restricted to applications in gas-particle flows, the present model is capable of simulating the dynamics of both turbulent gas-particle and liquid-particle flows. The model predictions have been compared with several dilute turbulent fluid-particle experimental data found in the literature. Although a large body of experimental works exists for turbulent fluid-particle flows in the literature, a majority of those works exhibits either no interstitial fluid effect (ef ≈ es) or very significant interstitial fluid effect (e f << es). In order to thoroughly assess the predictive capability of the present model, detailed gas-particle flow data having intermediate ef values have been obtained by conducting Laser Doppler Velocimetry (LDV) experiments of a downward gas-particle flow in a vertical pipe. The ef values are modified in the experiments by varying either the particle loading or the Reynolds number. In general, good agreement is found between the model predictions and the experimental data for both the fluid and particle phase at the level of the mean and fluctuating velocity. Lastly, Reynolds number (Re) dependence of gas-phase turbulence in gas-particle flow has been investigated experimentally using two particle sizes and two particle densities. The experimental results at a dilute particle loading suggest that the Re dependence of the gas-phase mean and fluctuating velocities vary depending on the particle density, but not on the particle size. In addition, the gas turbulence, which is dampened at low Re compared to the single-phase flow, is enhanced at high Re due to the change in the segregation pattern of the particles at high Re.
Degree
Ph.D.
Advisors
Curtis, Purdue University.
Subject Area
Chemical engineering
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