Interface-Resolved Simulations of Reactor Flows

Fang, Jun; Cambareri, Joseph J.; Li, Mengnan; Saini, Nadish; Bolotnov, Igor A.

doi:10.1080/00295450.2019.1620056

Cited by 14 publications

(4 citation statements)

References 59 publications

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“…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: 64%

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

Fan

Fang

Bolotnov

2020

Exp. Comput. Multiph. Flow

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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.

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Section: Flow Solver and Interface Capturing Approachmentioning

confidence: 64%

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

Fan

Fang

Bolotnov

2020

Exp. Comput. Multiph. Flow

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“…DNS (or even LES) scale simulations of PWR sub-channels are usually performed on axially periodic domains [33,54], which allow the flow to develop to a quasi-steady turbulent state. Here, however, the presence of the droplets and spacer-grids and mixing vane structures preclude the option of employing a periodic domain.…”

Section: Geometry and Simulation Propertiesmentioning

confidence: 99%

“…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

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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.

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“…Simulation has been widely used to describe complex systems, such as reactors, in order to design new geometries, determine the volume of new reactors, analyze different scenarios, determine the conversion and optimize operating variables [1] , [2] , [3] . Solar reactors are used in water treatment research to degrade pollutants by advanced oxidation process.…”

Section: Introductionmentioning

confidence: 99%

New approach for the dimensionless analysis of a unidirectional flow solar reactor based on Damköhler's number profiles

Otálvaro-Marín

Machuca-Martínez

2021

Heliyon

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A methodology for the analysis of the behavior of complex reactors based on the construction of profiles of a dimensionless number (Damköhler) for each main chemical species ( ) was proposed. A 4-chlorophenol mineralization reaction in a heterogeneous solar reactor with suspended TiO 2 and addition of H 2 O 2 with tubular geometry and radiation collectors, fluid flow and a recirculation system was selected as a complex model system in order to validate the approach. The dynamic behavior of the reactor in dimensionless variables was modeled as a function of . Where ( , ) is a local property and grouped the optical and surface's properties of the catalyst, catalyst load, radiation intensity, the photon absorption rate, rate of non-photochemical reactions, the H 2 O 2 effect, the reaction rate of different stages like adsorption, attack of radicals, surface reactions, plus design and operation variables like reactor volume and volumetric flow. A coupling of orthogonal collocation and Runge-Kutta methods were used to solve the PDEs and carry out the simulations to the different experimental conditions, resulting in profiles of , , and conversion in function of time and space. The profiles proposed in the new methodology are capable of describing the disturbances in solar reactors, to indicate consumption and generation rates, instantaneous changes of reaction rate, to describe competitive reactions and quenching effects and to determine equilibrium concentrations, all of the above at each time and space. Therefore, this approach is a analysis tool of reactors which complements the concentration profile. This methodology can be extended to other reactive systems, adapting the intrinsic reaction rates., [10], where is the ratio of the reaction rate to the global movement rate of the fluid, or alternatively, the product

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Interface-Resolved Simulations of Reactor Flows

Cited by 14 publications

References 59 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

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

New approach for the dimensionless analysis of a unidirectional flow solar reactor based on Damköhler's number profiles

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