Multiphase Flow Modeling

What is a Multiphase Flow?
Multiphase flow is a phenomena of simultaneous flow of mixtures of phases such as gases (like bubbles) in a liquid, or liquid (like droplets) in gases and similar such flows.
By multiphase flow we mean that its a mixture of phase and each phase in it has a distinct velocity field.
Why study Multiphase Flow?
• Multiphase flows are found in various industrial applications like chemical reactors and process flow industries.
• Natural and environmental flows like rivers and cloud formation involve multiphase flows.
• In practical flows it is difficult to isolate single phase isolated flow phenomena.
• Knowledge of multiphase flow physics is extremely important to conduct any experimental or simulation studies.
• Multiphase flow is a very vast discipline of study. It involves study of fluid mechanics, heat transfer, mass transfer and energy transfer.
Classification of Multiphase flows:
Multiphase flows are generally classified on the basis of:
• number of phases
• types of phases
• size of phases
• the interaction between the phases.

Based on these parameters they are further classified as follows:

• Dispersed Phase Flow: In this type of flow one of the phases is in the form of discrete elements. There is no connection between these discrete phase elements that may be in the form of particles or droplets. E.g.: Droplets in gas, bubbles in liquid etc. It is thus a mixture of different sized droplets of particles dispersed around a continuous media.
• Separated Flows: In such types of flows the two phases involved are separated by a distinct line of contact. This basically means that we can travel from one location to another in the same phase and remain in the same medium. E.g.: Annular flow where there is a liquid layer along the pipe wall and a gaseous inner core. Thus in this flow, one phase can be distinctly separated from another.
• Gas-Liquid Flows: As the name suggests one of the phases is in gaseous form while the other in liquid state. They can be in different forms like bubbly flow and annular flow.
• Gas–Solid Flows: In such types of flows we generally have gas with suspended solid particles. Granular flows are also among this where particle–particle and particle–wall interactions are more important than the forces due to the interstitial gas.
• Liquid–Solid Flows: In these types of flows solid particles are carried by liquid, also called as slurry flows. Here the solid particles will not have the distinct velocity field but will generally follow the liquid velocity field.
• Three-Phase Flows: Three-phase flows are also encountered in engineering problems. For example, bubbles in a slurry flow give rise to three phases flowing together. This is an emerging topic for research and computational modeling and is a very advanced and interesting branch of study under multiphase flows.
coming up next… Fundamental terminologies used in study of multiphase flows :
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