Slug-to-churn vertical two-phase flow regime transition study using an interface tracking approach

Zimmer, Matthew D.; Bolotnov, Igor A.

doi:10.1016/j.ijmultiphaseflow.2019.04.003

Cited by 28 publications

(10 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The adaptive mesh refinement capabilities used in PHASTA were also verified and it was shown to successfully capture wavy interface structures of annular flow as well as reduce the computational costs (Rodriguez et al, 2013). 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.…”

Section: Flow Solver and Interface Capturing Approachmentioning

confidence: 81%

“…Severe deformation may result in bubble break-up, which leads to more complex flow regimes. One such example is the slug bubble during the slug-to-churn flow regime transition (Zimmer and Bolotnov, 2019). As the gas flow rate increases, satellite bubbles are teared off from the slug bubble which contribute to the interface instability and eventually trigger the transition.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Fan

Fang

Bolotnov

2020

Exp. Comput. Multiph. Flow

View full text Add to dashboard Cite

The dynamics of bubble deformation has significant impacts on two-phase flow fundamentals such as bubble induced turbulence and flow regime transition. Despite the significant progress achieved by experimental studies on bubble deformation, certain limitations still exist especially for wide-range datasets. To significantly expand the flow conditions available from experiments, direct numerical simulation (DNS) is utilized to study the bubble-liquid interactions using finiteelement solver with level-set interface capturing method. Different from conventional investigations of bubble rising and deforming in stagnant liquids, a proportional-integral-derivative (PID) bubble controller is leveraged to maintain the bubble location in uniform liquid flow. This paper evaluates the reliability and reproducibility of the PID bubble controller for complex bubble deformation studies through a comprehensive set of verification and validation studies. An improved bubble deformation map is developed, based on Weber number and bubble Reynolds number, showing six zones for different deformation and break-up mechanisms. This research aims at producing virtual experiment level data source using interface resolved DNS and shedding light into the physics of interface dynamics. The insights obtained can be further incorporated in improved multiphase CFD models to guide the engineering designs and industrial processes where bubble deformation and break-up play a pivotal role.

show abstract

Section: Flow Solver and Interface Capturing Approachmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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

Fan

Fang

Bolotnov

2020

Exp. Comput. Multiph. Flow

View full text Add to dashboard Cite

show abstract

“…The largest loss of void is observed in mesh 9-10, although the difference is rather small with mesh 10-10 and 10-11. Quite interestingly, the average shape of the bubble tail varies from flat (9-10) to somewhat concave (10-10) and somewhat convex (10)(11). The streamlines indicate that the bubble itself consists of a large toroidal vortex with its rotational center relatively close to the tail.…”

Section: Simulation Strategy Meshing and Averagingmentioning

confidence: 98%

“…However, a deviation of the turbulent fluctuations in the wake of the Taylor bubble due to over-prediction of the loss of void of the Taylor bubble made the authors of [2] conclude that the LES mesh resolution is not sufficient to capture the break-up and bubble formation accurately. Meanwhile, other researchers have also performed high fidelity simulation of turbulent Taylor bubble flow, e.g., see [10] and [11].…”

Section: Introductionmentioning

confidence: 99%

LES of Turbulent Co-current Taylor Bubble Flow

Frederix

Komen

Tiselj

et al. 2020

Flow Turbulence Combust

View full text Add to dashboard Cite

The modeling and simulation of two-phase flows using CFD can contribute significantly to the topic of nuclear reactor safety, e.g., in the accurate prediction of the pressurized thermal shock phenomenon under two-phase conditions. However, there are still many challenges remaining in the development of a general two-phase model which is capable of capturing all two-phase flow regimes within the same setting, ranging from bubbly flow to large interface flow such as slug flow, Taylor bubble flow or stratified flow. One of those challenges is the appropriate representation of the behavior of turbulence at a large scale two-phase interface, and the subsequent break-up of such an interface into smaller structures. This requires the development and validation of more advanced two-phase turbulence models. The first step in this direction was made in [1], in which Egorov's idea of turbulence damping near a two-phase interface was generalized towards a more meshindependent formulation. For specific settings, the model could be calibrated to give good agreement with experimentally measured velocity and velocity fluctuation profiles of two-phase stratified flow. However, for real-world problems, a much more general interfacial turbulence damping model should be developed which adapts to local conditions automatically.

show abstract

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Saini

Bolotnov

2021

Fluids

Self Cite

View full text Add to dashboard Cite

In the dispersed flow film boiling regime (DFFB), which exists under post-LOCA (loss-of-coolant accident) conditions in pressurized water reactors (PWRs), there is a complex interplay between droplet dynamics and turbulence in the surrounding steam. Experiments have accredited particular significance to droplet collision with the spacer-grids and mixing vane structures and their consequent positive feedback to the heat transfer recorded in the immediate downstream vicinity. Enabled by high-performance computing (HPC) systems and a massively parallel finite element-based flow solver—PHASTA (Parallel Hierarchic Adaptive Stabilized Transient Analysis)—this work presents high fidelity interface capturing, two-phase, adiabatic simulations in a PWR sub-channel with spacer grids and mixing vanes. Selected flow conditions for the simulations are informed by the experimental data found in the literature, including the steam Reynolds number and collision Weber number (Wec={40,80}), and are characteristic of the DFFB regime. Data were collected from the simulations at an unprecedented resolution, which provides detailed insights into the continuous phase turbulence statistics, highlighting the effects of the presence of droplets and the comparative effect of different Weber numbers on turbulence in the surrounding steam. Further, axial evolution of droplet dynamics was analyzed through cross-sectionally averaged quantities, including droplet volume, surface area and Sauter mean diameter (SMD). The downstream SMD values agree well with the existing empirical correlations for the selected range of Wec. The high-resolution data repository from the simulations herein is expected to be of significance to guide model development for system-level thermal hydraulic codes.

show abstract

Slug-to-churn vertical two-phase flow regime transition study using an interface tracking approach

Cited by 28 publications

References 37 publications

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

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

LES of Turbulent Co-current Taylor Bubble Flow

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

Contact Info

Product

Resources

About