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 summary Program Title: varRhoTurbVOF CPC Library link to program files: http://dx.doi.org/10.17632/4t8z8vzyvs.2 Developer’s repository link: https://github.com/wenyuan-fan/varRhoTurbVOF_2 Licensing provisions: GPLv3 Programming 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?: Yes Reasons 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. References: [1] 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. [2] Y. Egorov, 2004. Validation of CFD codes with PTS-relevant test cases, 5th Euratom Framework Programme ECORA project, 91-116. [3] Wenyuan Fan, Henryk Anglart, 2019. Progress in Phenomenological Modeling of Turbulence Damping around a Two-Phase Interface, Fluids, 4(3), 136. [4] E.M.A. Frederix, A Mathur, D Dovizio, B.J. Geurts, E.M.J. Komen, 2018. Reynolds-averaged modeling of turbulence damping near a large-scale interface in two-phase flow, Nuclear Engineering and Design, (333), 122-130.

中文翻译：

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varRhoTurbVOF 2：改进的 OpenFOAM 流体求解器体积，具有高级湍流建模功能

摘要 varRhoTurbVOF 包含一组 OpenFOAM 流体体积 (VOF) 求解器，用于湍流等温多相流，它们是变密度不可压缩的。与官方对应的 Favre 平均速度和 Reynolds 平均速度共存于不同方程不同，新求解器在所有方程中一致使用 Favre 平均速度。此重大更新引入了对 varRhoTurbVOF 先前版本的三个主要改进。首先，实现扩展到等温和非等温相变两相流的 VOF 求解器，其中流动不再是不可压缩的。其次，为了引入向后兼容性并避免代码重复，重新设计了湍流模型构建程序，以便求解器可以在运行时根据输入文件确定湍流建模部分是否考虑了变密度效应。第三，用于基于 ω 的湍流模型的 Egorov 湍流阻尼模型是以其最新发展实现的。此外，还开发并实施了对基于 ϵ 的湍流模型的扩展。程序摘要 程序名称：varRhoTurbVOF CPC 库程序文件链接：http://dx.doi.org/10.17632/4t8z8vzyvs.2 开发者存储库链接：https://github.com/wenyuan-fan/varRhoTurbVOF_2 许可条款：GPLv3 Programming语言：C++ 以前版本的期刊参考：Wenyuan Fan，Henryk Anglart，2020。 varRhoTurbVOF：OpenFOAM 中用于湍流等温多相流的一组新的流体求解器，Computer Physics Communications, 247, 106876. 新版本是否取代以前的版本？：是 新版本的原因：新求解器和模型的实现；代码重新设计以保持向后兼容性。修订摘要：更新版本与之前的版本相比，主要有三个新特性： • [1] 中解决的问题存在于所有OpenFOAM VOF 求解器中，其中在湍流建模中忽略了可变密度效应。为了解决相变 VOF 求解器的这个问题，另外两个求解器，即 varRhoInterPhaseChangeFoam 和 varRhoInterCondensatingEvaporatingFoam 是基于它们的官方对应物实现的。• 重新设计了在单个求解器中构建湍流模型的过程。使用新的设计，求解器将根据用户输入构建湍流模型，考虑或不考虑可变密度效应。当后一种模式被激活时，求解器的行为就像他们的官方对应物一样。这样，在不引入代码重复的情况下实现了代码的向后兼容性。• 实施了 Egorov 湍流阻尼模型 [2]，这是一种流行的方法，用于从现象学上修改两相界面附近的湍流行为。除了原始模型，最近的修改，例如，新的长度尺度计算和非对称阻尼处理 [3]，也被实施。Egorov 模型仅适用于基于 ω 的湍流模型。在新版本中，遵循 [4] 中提出的想法，将模型扩展到基于 ϵ 的湍流模型，使得湍流阻尼模型适用于常用的湍流模型。问题性质：在 VOF 框架内，混合物的密度随相而变化。然而，在相当多的OpenFOAM VOF求解器中，动量方程考虑了变密度效应，而在湍流建模中却忽略了。因此，在动量方程和湍流量方程中分别并同时使用了法夫尔平均速度和雷诺平均速度，从而引入了严重的自相矛盾。在 [1] 中已经提出了这个问题的解决方案，但没有向后兼容性支持。此外，先前版本不支持相变求解器。湍流 VOF 模拟的另一个问题是，即使正确实施，仍需要进行某些修改以纠正界面周围的湍流行为。求解方法：根据 [1]，相变 VOF 求解器的扩展很简单。关于湍流模型的构建，在湍流模型中创建并使用了两个附加字段，即 rhoTurb 和 rhoPhiTurb 。如果用户选择使用变密度湍流模型，实际两相密度 rho 和质量通量 rhoPhi 将分别分配给 rhoTurb 和 rhoPhiTurb 。否则， rhoTurb 和 rhoPhiTurb 将分别使用单位和体积通量 phi 。这种运行时选择设计使求解器可以在两种模式下运行，既保证了向后兼容性，又避免了代码重复。湍流阻尼模型的实现也考虑了向后兼容性。在运行时，代码将通过检查相应方程的维数来自动确定混合物密度是否应包含在湍流阻尼模型中。附加说明： 提供了一本手册来介绍如何制定湍流阻尼建模以及如何使用该模型。需要强调的是，Egorov 阻尼模型是一种现象学模型。应针对任何给定的网格和流动条件仔细选择模型参数。参考文献： [1] Wenyuan Fan, Henryk Anglart, 2020. varRhoTurbVOF：OpenFOAM 中用于湍流等温多相流的一组新的流体求解器，Computer Physics Communications, 247, 106876. [2] Y. Egorov, 2004。使用 PTS 相关测试用例验证 CFD 代码，第 5 个 Euratom 框架计划 ECORA 项目，91-116。[3] Wenyuan Fan, Henryk Anglart, 2019. 两相界面湍流阻尼现象学建模进展, 流体, 4(3), 136. [4] EMA Frederix, A Mathur, D Dovizio, BJ Geurts, EMJ Komen, 2018. 两相流中大尺度界面附近湍流阻尼的雷诺平均建模，Nuclear Engineering and Design, (333), 122-130。