Numerical study on effects of granular deformations on dense powder conveying using a modified two-fluid model

Granular deformations exert significant effects on conveying dynamics, coupled with inherent multiscale nonlinearity and complex rheological characteristics of dense powder flows, necessitating further in-depth investigations to unveil dense powder conveying mechanisms. Based on the coupling of the multiple-state theory, granular deformations have been introduced into the modified two-fluid model (TFM) through the refinement of the mesoscopic solid-pressure model in this study. To validate the modified TFM, a dense powder conveying experiment featuring a built-in fluidization gas intake structure was conducted, in which the instability of startup behaviors, directly affecting the optimization of conveying strategies, have been preliminarily identified. Moreover, a comparative analysis with multiple experimental results demonstrates the accuracy and reliability of the developed numerical model, highlighting the necessity of accounting for granular deformations. Using the modified TFM, the startup behaviors of dense powder conveying were thoroughly analyzed, revealing effects of granular deformations on increasing peak powder flow rates and the solid-gas ratio, indicating the non-ideal linearity of powder flow rate and fluidization pressure, and illustrating the decompression process within the powder layer. Additionally, inhomogeneous local solid-pressure concentrations within the powder flow resulting from the internal structures and fluidizing gas, and their impacts on conveying dynamics were captured in the simulations. The findings could provide valuable insights into the details of dense powder conveying and present a novel numerical approach, contributing significantly to the design and optimization of granular systems.