Investigation of the lift and virtual mass force in gas-liquid flows with particle-resolved direct numerical simulation

CBET 1438143许多化学制造工艺在鼓泡塔反应器中进行，其中气泡分散在整个液体中以进行化学反应。 这些反应器被设计成包含大量小气泡以增加气相和液相之间的接触面积。 这些反应器内部的气-液流动的动力学和类似的多相过程通常使用称为双流体模型的数学模型来描述。 该项目的重点是通过明确考虑气泡之间的相互作用对模型中某些项的影响来改进双流体模型。 研究人员将通过使用气泡运动的计算模拟来评估这些关键术语，这些气泡运动解释了气泡之间的相互作用和气泡组件在流动中的发展。 然后将改进的双流体模型用于计算流体动力学模拟，以与实验数据进行比较，并帮助验证模型。 该项目的结果将有助于设计和优化一系列广泛的制造过程，如发酵，废水处理，藻类生长和抗生素生产。气液流动的体积平均双流体模型的准确性取决于估计气相和液相之间的动量传递的术语。 这些术语包括几种力，例如阻力、升力和虚拟质量力。 这些力通常是在流中有孤立气泡的情况下计算的。 该项目将研究流中相互作用的气泡组件对升力和虚拟质量力的影响，并将利用结果为双流体模型开发改进的动量交换项。 力将通过对球形浮力颗粒进行颗粒分辨直接数值模拟来确定，球形浮力颗粒是气泡变形可以忽略的极限中气泡的替代物。 模拟将用于开发表达式的升力和虚拟质量力中使用的双流体方程。 改进的双流体模型，然后将用于计算流体动力学模拟在广泛的操作条件下，实验数据可用于验证新开发的条款。

CBET 1438143Many chemical manufacturing processes are carried out in bubble column reactors in which gas bubbles are dispersed throughout a liquid to perform chemical reactions. These reactors are designed to contain a large number of small bubbles to increase the contact area between the gas and liquid phases. The dynamics of gas-liquid flow inside these reactors and in similar multiphase processes is often described using mathematical models called two-fluid models. This project focuses on improving two-fluid models by explicitly taking into account the effects of interactions among the bubbles on certain terms in the models. The investigators will evaluate these critical terms by using computational simulations of bubble motions that account for interactions among bubbles and the development of bubble assemblies in flow. The improved two-fluid model will then be used in computational fluid dynamic simulations to compare with experimental data and help validate the model. The results of the project will be useful to design and optimize a broad array of manufacturing processes such as fermentation, wastewater treatment, algae growth, and antibiotic production.The accuracy of volume averaged two-fluid models for gas-liquid flow depends on terms that estimate momentum transfer between gas and liquid phases. These terms include several forces such as drag, lift and virtual mass forces. These forces are usually evaluated for the case of an isolated bubble in the flow. This project will study the effects of assemblies of interacting bubbles in the flow on the lift and virtual mass forces, and will use the results to develop improved momentum exchange terms for two-fluid models. The forces will be determined by conducting particle-resolved direct numerical simulations of spherical buoyant particles, which are a surrogate for bubbles in the limit where bubble deformation can be neglected. The simulations will be used to develop expressions for the lift and virtual mass forces for use in the two-fluid equations. The improved two-fluid models will then be used in computational fluid dynamics simulations over a wide range of operating conditions for which experimental data are available to validate the newly developed terms.