A Second‐Order Turbulence Model Based on a Reynolds Stress Approach for Two‐Phase Flow—Part I: Adiabatic Cases

Abstract

In our work in 2008, we evaluated the aptitude of the code Neptune CFD to reproduce the incidence of a structure topped by vanes on a boiling layer, within the framework of the Neptune project. The objective was to reproduce the main effects of the spacer grids. The turbulence of the liquid phase was modeled by a first-order K-ε model. We show in this paper that this model is unable to describe the turbulence of rotating flows, in accordance with the theory. The objective of this paper is to improve the turbulence modeling of the liquid phase by a second turbulence model based on a R ij -ε approach. Results obtained on typical single-phase cases highlight the improvement of the prediction for all computed values. We tested the turbulence model R ij -ε implemented in the code versus typical adiabatic two-phase flow experiments. We check that the simulations with the Reynolds stress transport model (RSTM) give satisfactory results in a simple geometry as compared to a K-ε model: this point is crucial before calculating rod bundle geometries where the K-ε model may fail.

Comparison and uncertainty quantification of two-fluid models for bubbly flows with NEPTUNE_CFD and STAR-CCM+

“…The hydrodynamic closures tested in the two CFD codes are based on different strategies to cope with the complex interaction of the interfacial forces. In NEPTUNE_CFD, starting from a classical single-bubble closure for the lift force (Tomiyama et al, 2002), coupled to a calibrated wall force to reproduce the wall peak (Tomiyama, 2002), the lateral redistribution of void fraction is controlled through the recently derived generalized turbulent dispersion force of Laviéville et al (2015) coupled to the Reynolds stress based bubble turbulence treatment of Mimouni et al (2009). In STAR-CCM+, starting from the classic turbulence dispersion treatment of Burns (2004), the wall effects are introduced from analytical derivation of the near-wall void distribution incorporated in the turbulent dispersion regularization of Lubchenko (2017), in order to separate out the lift force in turbulent bubbly flow as the remaining sensitivity parameter.…”

“…Turbulence in the liquid phase is accounted for through a second-order, RS − E model (Mimouni et al, 2009). Two-phase extra contributions are included in the Reynolds Stress Tensor ",RS and Turbulent dissipation T " equations, corresponding to bubble-induced turbulence, writing as: U:-" ! "…”

“…Table 2 summarizes the prescribed interfacial forces and turbulence models utilized in NEPTUNE_CFD and STAR-CCM+ simulations. Rij-ε (Mimouni et al, 2009) Standard k-ε (Launder, 1974)…”

Extension of CFD Codes Application to Two-Phase Flow Safety Problems

“…The k-ε or Shear Stress Transport (SST) methods were used with some success by Morel et al [12,13,14,15], Mimouni et al [16], and Lucas et al, [17]. If the swirling flow past a spacer grid vane must be modelled, it is shown [18] that the SST models can perform better than the k-ε model. The LES approach has been evaluated in the simulations of a bubble column [19].…”

CFD calculations of flow pattern maps and LES of multiphase flows

“…The simulation of the dispersed fields with the two-fluid model has been widely studied with the NEPTUNE_CFD code by Mimouni et al (2009Mimouni et al ( ,2010Mimouni et al ( ,2011. Thus, the modelling effort concerns large interfaces.…”