This critical review paper outlines the recent progress in high-resolution numerical simulations of two-phase coolant flow in light water reactor–relevant geometries by resolving the water-vapor interface. Rapid development of capabilities in high-performance computing is creating exciting opportunities to study complex reactor thermal-hydraulic phenomena. Today’s advances in thermal-hydraulic analysis and interface-resolved simulations will help pave the way to the next level of understanding of two-phase flow behavior in complex geometries. This paper consists of two major parts: (1) a brief review of direct numerical simulation and interface tracking simulation and (2) several opportunities in the near future to apply cutting-edge simulation and analysis capabilities to address the nuclear-related multiphase flow challenges. The first part will discuss typical computational methods used for the simulations and provide some examples of the past work as well as computational cost estimates and affordability of such simulations for research and industrial applications. In the second part specific application examples are discussed, from adiabatic bubbly flow simulations in pressurized water reactor subchannel geometry to the modeling of nucleate boiling. The uniqueness of this study lies in the specific focus on applications with nuclear engineering interest as well as new generation modeling and analysis methodologies. Together with the ever-growing computing power, the related large-scale two-phase flow simulations will become indispensable for the improved scientific understanding of complex two-phase flow phenomena in nuclear reactors under normal operation and postulated accident conditions.