It is well-known that the multiphase flow has immense importance in various engineering technologies. The optimum design, the prediction of operational limits, and, very often, the safe control of a great number of important systems depend upon the availability of realistic and accurate mathematical models of two-phase flow. Multiphase flow has become increasingly important in a wide variety of engineering systems for their optimum design and safe operation. It is, however, by no means limited to today's modem industrial technology, and multiphase flow phenomena can be observed in a number of biological systems and natural phenomena that require better understandings. Multiple-phase is classified into different categories, i.e. Gas-solid mixture, Gas-liquid mixture, Liquid-solid mixture, Immiscible-liquid mixture, etc. Some significant applications are power systems, heat transfer systems, process systems, transport systems, information systems, lubrication systems, environmental control, geo-meteorological phenomena, biological systems, etc. It is evident that all the systems and components listed above are governed by essentially the same physical laws of transport of mass, momentum, and energy.

During recent decades, the principles of single-phase flow fluid dynamics and heat transfer have been relatively well understood. However, two-phase flow and thermo-fluid dynamics is an order of magnitude more complicated than single-phase flow due to the existence of a moving and deformable interface and its interactions with the two phases. However, in view of the practical importance of two-phase flow in various modem engineering technologies related to nuclear energy, chemical engineering processes, and advanced heat transfer systems, not enough efforts have been made in recent years to develop accurate general two-phase formulations, mechanistic models for interfacial transfer and interfacial structures, and computational methods to solve these predictive models.

Therefore, this Special Issue aims to encourage scholars to present their latest original studies or review articles. The analysis of fluid flows could be based on numerical/analytical simulations or experimental data that extend the bounds of existing methodologies to new contributions addressing current challenges and engineering problems. It is evident that with rapid advances in engineering technology, the demands for progressively accurate predictions of the systems in interest have increased. As the size of engineering systems becomes larger and the operational conditions are being pushed to new limits, the precise understanding of the physics governing these multiphase flow systems is indispensable for safe as well as economically sound operations.

Potential topics include but are not limited to the following:

• Measurements and theoretical development of multiphase flows properties
• Measurements and theoretical development of multiphase flows-enhanced phase change materials
• Numerical simulations relevant for potential applications
• New numerical models for estimation of multiphase flows heat transfer behaviour
• New innovative areas of multiphase flows applications in engineering
• Critical assessments and future directions in multiphase flows research
• Measurements and theoretical development of multiphase flows heat transfer
• Experimental and theoretical analysis on multiphase flows transport in porous media
• Nanomaterials and nanofluids preparation and characterization (nanoparticles, nanoPCM, nanofluids, nanosalts, ionanofluids, etc.)