Multiscale Two-Phase Bubbly Flow Modeling

Multiphase bubbly mixture flows are of importance in turbomachinery, pipelines, cooling systems, reaction towers, as well as in various applications in petroleum, chemical, geothermal, and nuclear industries. The presence of the gaseous component has a strong influence on performance and efficiency. The ability to predict the flow behavior accurately is essential in designing energy efficient two-phase flow process equipment. A major difficulty in modeling and simulation of such flows lies in the complex multiple lengths and multiple time scale nature of such flows. Conventional scientific and engineering approaches concentrate on either macroscopic averaged quantities or focus on two- phase interface tracking of identified important flow details and do not address the full flow. Therefore, a comprehensive model, which could resolve simultaneously the important scales, is required. The proposed research will develop a multi-scale two-phase flow simulation method capable of accurately representing bubbly flows at the various scales. The model will include a continuum- based phase averaged model for the macro-scales and a discrete bubble/particle model for the micro-scales. These will be integrated into a single code that automatically switches between the two models at different times or in different locations of the studied geometry and allows conversion of discrete bubbles into a continuum description or a liquid-gas free surface, and vice versa, depending on bubble and cavities evolution and space concentration. Commercial Applications and Other Benefits: A multi-scale approach based on state-of-the-art numerical techniques will result in a commercial code for generalized bubble flow simulations which can accurately capture important characteristics of cavitating and high void fraction multiphase flows. This software will be able to describe dilute mixtures as well as mixtures that result in large cavities, bubble clouds, separated flows, etc. This software will enable researchers in chemical, oil and gas, nuclear, and marine industries to conduct design studies and to improve energy efficiency of their processes and devices. These applications will strengthen the competitiveness of US industries equipped with advanced systems.