Faculty Publications

This paper presents a two-dimensional finite volume method-based computational model to understand the mixing phenomena in a double wall oscillating square lid driven cavity. The study is mainly performed to see the effect of Schmidt number by employing SIMPLE algorithm to solve the discretized equations of mass, momentum and concentration. The developed code in FORTRAN is validated by comparing with previous works. Numerical simulations are conducted on parallel and antiparallel wall oscillations and found that low Schmidt number provides better mixing in both cases. Â© 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Hydrodynamics and residence time distribution (RTD) of fluid elements are key parameters to characterize the performance of stirred vessel. They are governed by geometric and operating parameters of the stirred vessel (SV). In the present work, the performance of the stirred vessel is studied using computational fluid dynamics (CFD) with realizable k-ϵ turbulence model. The multiple reference frame and sliding mesh approach are used for impeller motion. The solid-liquid flow and associated solid suspension characteristics are predicted using the two-fluid model (Euler-Granular). The performance of the stirred vessel is characterized by analyzing predicted velocity magnitude, solid concentration (suspension quality), and solid sedimentation. This is compared with the stirred vessel with draft tube baffle configuration (three inner baffles and six outer baffles). The recirculatory flow in draft tube SV helps to achieve uniform suspension and less sedimentation. Further, CFD simulations are carried out in Lagrangian way to analyze chaotic mixing among fluid elements. This is qualitatively analyzed using Poincaré map and quantitatively evaluated using Shannon entropy. The extent of chaotic mixing in draft tube SV is found to be high. The performance of the stirred vessel is further investigated through stimulus-response tracer techniques (RTD) to detect design flaws such as bypass and dead zones. This is analyzed for a wide range of operating parameters and identified optimum conditions (flow rate, impeller speed) for the operation of SV. The four different outlet pipe locations are chosen in SV. The bypass and dead volume are analyzed accordingly, and an optimum outlet pipe location is found. To reduce the extent of non-ideal parameters, three different gas source locations are considered and gases are dispersed in the form of bubbles. The gas dispersion at optimum gas injection point is found to reduce non-ideal parameters and improve the design of stirred vessel. © 2022 Author(s).

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