Stability-driven Structure Evolution: Exploring the Intrinsic Similarity Between Gas-Solid and Gas-Liquid Systems

As the core of the Energy-Minimization Multi-Scale (EMMS) approach, the so-called stability condition has been proposed to reflect the compromise between different dominant mechanisms and believed to be indispensable for understanding the complex nature of gas-solid fluidization systems. This approach was recently extended to the study of gas-liquid bubble columns. In this article, we try to analyze the intrinsic similarity between gas-solid and gas-liquid systems by using the EMMS approach. First, the model solution spaces for the two systems are depicted through a unified numerical solution strategy, so that we are able to find three structural hierarchies in the EMMS model for gas-solid systems. This may help to understand the roles of cluster diameter correlation and stability condition. Second, a common characteristic of gas-solid and gas-liquid systems can be found by comparing the model solutions for the two systems, albeit structural parameters and stability criteria are specific in each system: two local minima of the micro-scale energy dissipation emerges simultaneously in the solution space of structure parameters, reflecting the compromise of two different dominant mechanisms. They may share an equal value at a critical condition of operating conditions, and the global minimum may shift from one to the other when the operating condition changes. As a result, structure parameters such as voidage or gas hold-up exhibit a jump change due to this shift, leading to dramatic structure variation and hence regime transition of these systems. This demonstrates that it is the stability condition that drives the structure variation and system evolution, which may be the intrinsic similarity of gas-solid and gas-liquid systems