VarRhoTurbVOF 2: Modified OpenFOAM volume of fluid solvers with advanced turbulence modeling capability

Abstract

varRhoTurbVOF contains a set of OpenFOAM volume of fluid (VOF) solvers for turbulent isothermal multiphase flows, which are variable-density incompressible. Unlike their official counterparts, where Favre-averaged and Reynolds-averaged velocities coexist in different equations, new solvers use Favre-averaged velocities consistently in all equations. This major update introduces three main improvements to the previous version of varRhoTurbVOF. First, the implementation is extended to VOF solvers for isothermal and non-isothermal phase change two-phase flows, where the flow is no longer incompressible. Second, in order to introduce backward compatibility and to avoid code duplication, the turbulence model construction procedure is redesigned such that solvers can determine whether the variable-density effect is considered or not in the turbulence modeling part based on the input file at run time. Third, the Egorov turbulence damping model for ω-based turbulence models is implemented with its most recent developments. Plus, an extension to ϵ-based turbulence models is developed and implemented. Program summaryProgram Title: varRhoTurbVOFCPC Library link to program files:http://dx.doi.org/10.17632/4t8z8vzyvs.2Developer’s repository link:https://github.com/wenyuan-fan/varRhoTurbVOF_2Licensing provisions: GPLv3Programming language: C++Journal reference of previous version: Wenyuan Fan, Henryk Anglart, 2020. varRhoTurbVOF: A new set of volume of fluid solvers for turbulent isothermal multiphase flows in OpenFOAM, Computer Physics Communications, 247, 106876.Does the new version supersede the previous version?: YesReasons for the new version: Implementation of new solvers and models; code redesign to maintain backward compatibility.Summary of revisions: The updated version mainly has three new features in comparison with the previous version: •The issue addressed in [1] exists in all OpenFOAM VOF solvers where the variable-density effect is neglected in the turbulence modeling. In order to solve this issue for phase change VOF solvers, two additional solvers, namely, varRhoInterPhaseChangeFoam and varRhoInterCondensatingEvaporatingFoam, are implemented based on their official counterparts.•The procedure of constructing the turbulence model inside individual solvers is redesigned. Using the new design, solvers will construct turbulence models with or without the variable-density effect being considered based on the user input. When the latter mode is activated, solvers will behave just like their official counterparts. In such a way, the backward compatibility of the code is achieved without introducing code duplications.•The Egorov turbulence damping model [2], which is a popular approach to phenomenologically modify turbulence behaviors near a two-phase interface, is implemented. In addition to the original model, recent modifications, e.g., a new length scale calculation and asymmetric damping treatments [3], are implemented as well. The Egorov model only works with ω-based turbulence models. In the new release, the model is extended to ϵ-based turbulence models following the idea proposed in [4] such that the turbulence damping model is applicable to commonly used turbulence models.Nature of problem: Within the VOF framework, the mixture has a density changing with phases. However, in quite a few OpenFOAM VOF solvers, the variable-density effect is considered in the momentum equation but neglected in the turbulence modeling. As a result, Favre-averaged velocities and Reynolds-averaged velocities are used in the momentum equation and turbulence quantity equations, respectively and simultaneously, introducing a severe self-inconsistency. Solutions to this problem have been proposed in [1] with no backward compatibility support. Also, no phase change solvers are supported in the previous version. Another issue with turbulent VOF simulations is that, even with the correct implementation, certain modifications are still needed to correct the turbulence behavior around the interface.Solution method: The extension to phase change VOF solvers is straightforward according to [1]. Regarding the construction of turbulence models, two additional fields, namely, rhoTurb and rhoPhiTurb, are created and used in turbulence models. If the user chooses to use the variable-density turbulence models, real two-phase density rho and mass flux rhoPhi will be assigned to rhoTurb and rhoPhiTurb, respectively. Otherwise, rhoTurb and rhoPhiTurb will use unity and volume flux phi, respectively. This run time selection design enables solvers to operate in two modes, which guarantees the backward compatibility and avoids code duplications. The implementation of the turbulence damping model also takes the backward compatibility into account. At run time, the code will automatically determine whether the mixture density should be included in the turbulence damping model by checking the dimension of the corresponding equation.Additional comments: A manual is provided to introduce how the turbulence damping modeled is formulated and how to use the model. It should be emphasized that the Egorov damping model is a phenomenological model. Model parameters should be carefully selected for any given mesh and flow condition.