Numerical Investigation of Two-Phase Flow Transition and Heat Transfer in a V-Shaped Cavity with Stratified Fluids

Articles in Press

Document Type : Research Paper

Authors
Md. Mahafujur Rahaman 1 , 2
Sidhartha Bhowmick 2
Goutam Saha 3
Suvash C. Saha 4
1 Department of Computer Science and Engineering, Z. H. Sikder University of Science and Technology, Shariatpur, 8024, Bangladesh
2 Department of Mathematics, Jagannath University, Dhaka, 1100, Bangladesh
3 Department of Mathematics, International University of Business Agriculture and Technology, Dhaka-1230, Bangladesh
4 School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, North South Wales, 2007, Australia
10.22055/jacm.2026.49109.5741
Abstract
Two-phase air-water flow is very important in many industrial systems, including chemical reactors, nuclear power plants, refrigeration systems and petrochemical technologies. Motivated by their relevance, the present work examines natural convection (NC), heat transfer (HT), and entropy generation (Egen) inside a V-shaped cavity containing two stratified fluids, namely air and water. The numerical simulations are performed applying the volume of fluid (VOF) method, which effectively captures interfacial dynamics between the phases. The physical configuration studied is one where water is filled in the lower part of the cavity, while air is filled in the upper part of the cavity and the heating is applied at the fluid interface. Thermal stratification is applied on the inclined walls, from the interface to the top in the air phase and from the interface to the bottom in the water phase. User-defined functions (UDFs) are used in FLUENT to apply thermal boundary conditions and the governing equations are discretized by using finite volume method (FVM). The VOF model numerically simulates the transport equations for each phase individually and couples them together through the interaction forces on the interfaces. The simulations are carried out by using Prandtl number (Pr) of 0.71 for air and 7.01 for water and Rayleigh number (Ra) ranging from 100 to 108. Streamline and isotherm distributions, temperature time series (TTS), bifurcation analyses, average Nusselt number (Nuavg) time series, Egen, and average Bejan number (Beavg) distributions are used to analyze the flow and thermal characteristics. The results show a series of transitions from steady to chaotic flow as Ra is increased. A pitchfork bifurcation is observed in both phases between Ra = 9 × 105 and 106. Subsequently, a Hopf bifurcation is identified in the air phase between Ra = 5 × 106 and 107. In the air phase, a transition from periodic to chaotic flow occurs at Ra = 5 × 107, while the flow in the water phase remains in a weakly rotational state. Moreover, at higher Ra, Egen due to fluid friction (FF) becomes dominant in the air phase. The findings also show that both the HT rate and Egen in the air phase is significantly greater than that in the water phase.
Keywords
Stratified fluid
Two-phase flow
Natural convection
Entropy generation
VOF method
Subjects

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