Interface capturing simulations of droplet interaction with spacer grids under DFFB conditions

Two-Phase Turbulence Statistics from High Fidelity Dispersed Droplet Flow Simulations in a Pressurized Water Reactor (PWR) Sub-Channel with Mixing Vanes

“…Details of the numerical method, including the challenges encountered for large-scale representative DFFB simulations, were discussed in detail in Saini and Bolotnov [35] (and Saini [43]). Here, we provide a brief overview of the numerical method, focusing on the details specific to the presented simulations.…”

“…The rapid advent of high-performance computing (HPC) systems has only recently enabled excursions into large-scale interface-resolved simulations of complex two-phase flows. Using the strongly parallel scaled, finite-element-method-based code-PHASTA (Parallel Hierarchic Adaptive Stabilized Transient Analysis) [28,29]-and the level-set interface capturing method [30], two-phase simulations have been performed for conditions representative of PWR flow regimes, including bubbly flows [31][32][33], slug-to-churn flow [34] and the DFFB regime [35] (from our prior work). Interface tracking method [36] and immersed boundary method [37] have also been used for simulating bubbly flows; however, their challenging numerical implementation precludes applicability to complex geometries and complex interface topologies.…”

“…In this work, we significantly extend the analysis presented in Saini and Bolotnov [35]. Interface capturing simulations were performed using PHASTA [29] for conditions representative of the DFFB regime.…”

“…Interface capturing simulations were performed using PHASTA [29] for conditions representative of the DFFB regime. The two-phase dimensionless properties in the present work were for a steam-water system at 30 psi (see Table 1), while in [35] it was chosen to represent an air-water system at atmospheric conditions, and three sets of simulations were performed for collision Weber number, We c ∈ {40, 55, 80} (Equation ( 14)). Further, data were collected from the simulations at a significantly enhanced spatial resolution, which enabled detailed cross-sectional analysis of the turbulence statistics and allowed unprecedented insight into the effects of spacer-grids and mixing vanes and the presence of droplets on turbulent flow features.…”

Validation and uncertainty quantification of multiphase-CFD solvers: A data-driven Bayesian framework supported by high-resolution experiments

“…The main challenge is the treatment of the interface between two phases. Directly resolving the interfaces with methods like level set [5] require formidable computational resources. While considering the two-phase as a mixture such as the homogeneous model could oversimplify the complex interfacial exchange between the two phases.…”