Numerical simulation of cryogenic flow with phase change using sharp interface cut-cell method
Cryogenic fluids find wide use in many different types of industries as well as space applications, where they may be used as the liquid fuel or the cryogen for other vital support systems. Therefore the transportation, handling and storage of cryogenic flow under microgravity in space missions is an important design concern. During their transportation through the pipes in a spacecraft, because of strong heat flux from wall, a rapid quenching process with voracious boiling of the cryogen takes place. This can subject the piping system to extreme thermal stresses due to sudden contraction. Due to strong vaporization and resulting two-phase flow, the mass flow rate of cryogenic flow will decrease. The insufficient flow rate can cause many problems in the spacecraft. Therefore a thorough physical understanding of the phase change phenomenon in cryogenic flow under microgravity is very important. Investigation of cryogenic chill down under microgravity is not easy because it is not easy to create the microgravity conditions on earth. Most of the experiments on quenching under microgravity have been done on board special aircrafts like NASA's KC-135. The cost of performing these experiments is very high. Moreover, it is not easy to collect experimental data in flight.
In this research work, numerical simulation techniques are used instead of experiments. In numerical simulation, the microgravity is easily modeled and the cost is much less than performing experiments. The sharp interface method (SIM) with cut-cell technique (SIMCC) is adopted to handle the two-phase flow computations. In SIM, the background grid is the Cartesian grid and the explicit interfaces are embedded in the computation domain dividing the entire domain into different sub-domains corresponding to various phases. In SIM, each phase has its own set of governing equations. The interfacial conditions act as the link between different phases. The cut-cell technique is utilized to handle the non-rectangular cells produced by the intersection of interfaces with the Cartesian grid. The conservative properties of the finite volume method can be satisfied better near the interface using cut-cells. The interface is treated as an entity with zero thickness with no volume association. With the explicit geometrical information about the interface and high resolution numerical schemes, the heat flux near the interface can be evaluated more accurately than by any other multiphase techniques.
This research aims to expand the scope of the SIMCC method by several enhancements like multigrid methods and third-order upwind differencing scheme for the convective term. These enhance the performance and stability of the SIMCC and improve its capability to handle the very challenging task of simulating internal multiphase flows. The specific focus of this research is inverted annular film boiling regime. Various physical mechanisms that influence the flow patterns and heat transfer characteristics during the transportation under reduced gravity are investigated.