Grid studies for the simulation of resolved structures in an Eulerian two-fluid framework

Gauss, F; Lucas, Dirk; Krepper, Eckhard

doi:10.1016/j.nucengdes.2016.06.009

Cited by 14 publications

(11 citation statements)

References 15 publications

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“…Gauss et al 40 propose to set the model constant to

{C}_d=0.22

in order to reproduce consistent bubble rising velocities on coarse to very coarse grids. With that value for the model parameter in combination with the hybrid model formulation under investigation, this turns out to cause disintegration of a gas bubble on coarse computational grids.…”

Section: Adaptive Drag Modelingmentioning

confidence: 99%

Momentum exchange modeling for coarsely resolved interfaces in a multifield two‐fluid model

Meller

Tekavčič

Krull

et al. 2023

Numerical Methods in Fluids

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Morphology‐adaptive multiphase models are becoming more established for the numerical description of complex gas‐liquid flows adapting dynamically to the local flow morphology. In the present study, two different numerical methods originally designed for distinct flow morphologies are combined, namely the volume‐of‐fluid and the Euler–Euler method. Both edge cases have been proven to be capable of delivering reliable predictions in the respective use cases. The long‐term goal is to improve the prediction of gas‐liquid flows, regardless of the flow regime in a specific application. To capture the system dynamics with a given grid resolution, the flow fields need to be predicted as precise as possible, while the shape of structures such as gas bubbles need to be recovered adequately in topology and shape. The goal is to obtain reliable predictions on intermediate mesh resolutions rather than relying on fine meshes requiring more computational resources. Therefore, a procedure is proposed to locally measure the degree of resolution. With this information, the hydrodynamics in the interface region can be controlled by means of a dedicated interfacial drag formulation in order to improve simulation results across several levels of spatial resolution. A modified formulation of buoyancy is proposed to prevent unphysical oscillations of vertical velocity near a horizontal interface. The functionality is demonstrated in a three‐dimensional case of a gas bubble rising in stagnant liquid and in a co‐current stratified air‐water channel flow in two‐dimensional space. The choice of these different applications demonstrates the general applicability of the proposed model framework.

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“…Gauss et al 40 propose to set the model constant to

{C}_d=0.22

Section: Adaptive Drag Modelingmentioning

confidence: 99%

Momentum exchange modeling for coarsely resolved interfaces in a multifield two‐fluid model

Meller

Tekavčič

Krull

et al. 2023

Numerical Methods in Fluids

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“…Such a no‐slip interface condition is reasonable, if the resolution of the computational grid is fine enough to resolve interfacial structures 9 . In contrast to a homogeneous model, the two‐fluid model is able to allow for a tangential slip velocity between both phases, which is an appropriate approach to model interfaces in an underresolved manner 39 . For the sake of simplicity in the present work, the model framework is setup, such that all relative velocity components between multiple phases are identical in the region of a shared interface.…”

Section: Modelingmentioning

confidence: 99%

“…Furthermore, the choice of a two fluid model in principle allows for a nonzero slip velocity between two continuous phases at an interface. Gauss et al 39 showed that such an interfacial slip allows for the description of large interface structures, such that the rising velocity of a single bubble can be predicted correctly, even on numerical grids, which are to coarse to fully resolve physical processes on all scales.…”

Section: Introductionmentioning

confidence: 99%

Basic verification of a numerical framework applied to a morphology adaptive multifield two‐fluid model considering bubble motions

Meller

Schlegel

Lucas

2020

Numerical Methods in Fluids

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Summary A morphology adaptive modeling framework is derived that is able to handle computationally efficiently dispersed as well as resolved interfacial structures coexisting in the computational domain with the same set of equations. The Eulerian multifield two‐fluid model is combined with the compact momentum interpolation method for multiple phases, which has been proposed in the literature as an extension to the Rhie‐Chow pressure‐velocity coupling. Additionally to the interfacial drag force, the virtual mass force is consistently accounted for in the model. Utilizing a specialized interfacial drag formulation, large interfacial structures can be described with the presented method in a volume‐of‐fluid‐like manner, additionally to the disperse description. The strong phase coupling due to the drag closure model in interfacial regions is resolved with a partial elimination algorithm, which is adapted to work in an approximate manner for more than two phases via a sum formulation. The presented model is implemented in the C++ library OpenFOAM and solver performance is compared with results obtained with the homogeneous model approach in two cases of a single rising gas bubble for two‐ and three‐dimensional space, respectively. Additionally, for both three‐dimensional cases, the results are compared with experimental data. Finally, the presented method's capability of representing dispersed and resolved interfacial structures at the same time is demonstrated with two test cases: a two‐dimensional gas bubble, rising in a liquid, which is laden with micro gas bubbles, and a two‐dimensional stagnant stratification of water and oil, sharing a large‐scale interface, which is penetrated by micro gas bubbles.

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“…In the case of two-phase simulation, usually, the volume of fluid (VOF) model is employed [20,40,41]. The computation is performed in a fixed grid solving only one momentum equation, which is shared by both fluids [42]. Generally, a very fine mesh is required to resolve the interface, e.g., [40].…”

Section: Introductionmentioning

confidence: 99%

Modeling of the Free-Surface Vortex-Driven Bubble Entrainment into Water

Putra

Lucas

2020

Water

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The recently developed GENTOP (Generalized Two Phase Flow) concept, which is based on the multifield Euler‒Euler approach, was applied to model a free-surface vortex—a flow situation that is relevant for hydraulic intake. A new bubble entrainment model has been developed and implemented in the concept. In general, satisfactory agreement with the experimental data can be achieved. However, the gas entrainment can be significantly affected by several parameters or models used in the CFD (Computational Fluid Dynamics) simulation. The scale of curvature correction C s c a l e in the turbulence model, the coefficient in the entrainment model C e n t , and the assigned bubble size to be entrained have a significant influence on the gas entrainment rate. The gas entrainment increases with higher C s c a l e values, which can be attributed to the stronger rotation captured by the simulation. A smaller bubble size gives higher gas entrainment, while a larger bubble size leads to a smaller entrainment. The results also show that the gas entrainment can be controlled by adjusting the entrainment coefficient C e n t . Based on the modeling framework presented in this paper, further improvement of the physical modeling of the entrainment process should be done.

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Grid studies for the simulation of resolved structures in an Eulerian two-fluid framework

Cited by 14 publications

References 15 publications

Momentum exchange modeling for coarsely resolved interfaces in a multifield two‐fluid model

Momentum exchange modeling for coarsely resolved interfaces in a multifield two‐fluid model

Basic verification of a numerical framework applied to a morphology adaptive multifield two‐fluid model considering bubble motions

Modeling of the Free-Surface Vortex-Driven Bubble Entrainment into Water

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