On the use of physical boundary conditions for two-phase flow simulations: Integration of control feedback. (4th October 2018)

• Record Type: Journal Article
• Authors: Agnaou, Mehrez; Treeratanaphitak, Tanyakarn; Mowla, Amir; Ioannidis, Marios; Mohieddin Abukhdeir, Nasser; Budman, Hector
• Is Part Of: Computers & chemical engineering. Volume 118(2018)
• Page Start: 268
• Page End: 282
• Publication Date: 2018-10-04
• Subjects: Two-phase flow -- Computational fluid dynamics -- Euler–Euler model -- Simulations -- Control; Chemical engineering -- Data processing -- Periodicals; 660.0285
• DOI: 10.1016/j.compchemeng.2018.08.012
• Languages: English
• ISSNs: 0098-1354

Abstract

Highlights: The impact of inlet boundary conditions on two-phase flow CFD solutions is studied. The two-phase upward flow in a vertical pipe is modeled using the Euler–Euler model. Solutions using inlet pressure and velocity Dirichlet boundary conditions differ. The gas phase distribution is strongly dependent on the inlet conditions. A control scheme is used to enforce the Dirichlet pressure boundary and flow rates. Abstract: The sensitivity of two-phase flow simulations using the Euler–Euler model on the inlet boundary conditions (BCs) is studied. Specifically, the physical relevance of Dirichlet uniform inlet velocity BCs is studied which are widely used due their simplicity and the lack of a priori knowledge of the slip velocity between the phases. It is found that flow patterns obtained with the more physically realistic uniform inlet pressure BCs are radically different from the results obtained with Dirichlet inlet velocity BCs, refuting the argument frequently put forward that Dirichlet uniform inlet velocity BCs can be interchangeably used because the terminal slip velocity is reached after a short entrance region. A comparison with experimental data is performed to assess the relevance of the flows obtained numerically. Additionally, a multivariable feedback control method is demonstrated to be ideal for enforcing desired flow rates for simulations using pressure BCs.