Interface tracking simulations of bubbly flows in PWR relevant geometries

Abstract

The advances in high performance computing (HPC) have allowed direct numerical simulation (DNS) approach coupled with interface tracking methods (ITM) to perform high fidelity simulations of turbulent bubbly flows in various complex geometries. In this work, we have chosen the geometry of the pressurized water reactor (PWR) core subchannel to perform a set of interface tracking simulations (ITS) with fully resolved liquid turbulence. The presented research utilizes a massively parallel finite-element based code, PHASTA, for the subchannel geometry simulations of bubbly flow turbulence. The main objective for this research is to demonstrate the ITS capabilities in gaining new insight into bubble/turbulence interactions and assisting the development of improved closure laws for multiphase computational fluid dynamics (M-CFD). Both single-and two-phase turbulent flows were studied within a single PWR subchannel. The analysis of numerical results includes the mean gas and liquid velocity profiles, void fraction distribution and turbulent kinetic energy profiles. Two sets of flow rates and bubble sizes were used in the simulations. The chosen flow rates corresponded to the Reynolds numbers of 29,079 and 80,775 based on channel hydraulic diameter (D h) and mean velocity. The finite element unstructured grids utilized for these simulations include 53.8 million and 1.11 billion elements, respectively. This has allowed to fully resolve

Complex bubble deformation and break-up dynamics studies using interface capturing approach

“…More recently, a slug-to-churn flow regime transition study reported favorable agreement between PHASTA results and the existing experimental and analytical results for complex two-phase flow regimes (Zimmer and Bolotnov, 2019). The two-phase flow simulation capability can also be extended to even larger engineering problems, such as nuclear reactor subchannels (Fang et al, 2017(Fang et al, , 2018(Fang et al, , 2020.…”

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

“…Data from probes in each loci from all quadrants at corresponding wall distance locations are averaged, which yields the mean wall distance function trend for the selected lateral plane (for further details on data averaging, see [35]). The inlet profile was compared with the DNS results for flow between parallel plates by Lee et al [52] and flow in a sub-channel, with similar geometrical specifications as the present work, by Fang et al [60]. Considering the canonical linear Log law of the wall, Figure 5 shows the normalized principal Reynolds stresses, = 〈 〉/ and normalized turbulent kinetic energy (TKE), = 0.5 〈 ′〉/ , compared with the trends obtained from Lee et al [52] and Fang et al [60].…”

Verification of bubble tracking method and DNS examinations of single- and two-phase turbulent channel flows

“…More geometric details are listed in Table 3. Although the investigated Reynolds number is only roughly a sixth of that under the realistic PWR flow condition [5], it is still much higher than what one can find in the literature for DNS studies on reactor coolant flow [9]. In DNS, the grid spacing must be sufficiently fine to capture the small scales of interest.…”

“…As an indispensable requirement for DNS solver, the excellent scaling performance of PHASTA has already been demonstrated in massively parallel simulations (up to 786,432 cores) [4]. PHASTA can be also utilized in two-phase flow simulations by incorporating the level set method to track the gas-liquid interface [5]. For the details of code FTC3D please refer to previous publication [6].…”