Abstract In this paper we present the algorithm and implementation of an open-source immersed boundary code sdfibm , which is based on OpenFOAM v6 and written in C++. The immersed boundary method (“ibm” of the name) treats the velocity field as the volume average of fluid and solid velocities, and applies the volume-average discrete forcing to account for the fluid–solid interaction. The signed distance field (“sdf” of the name) representation of the solid shape, together with the proposed pyramid decomposition method, allow accurate calculations of the volume fraction field created by solids overlapping with an arbitrary unstructured fluid mesh. SDF removes the need of intersection test between the solid and fluid mesh, or the discretization and re-sampling of the solid shape. Users can freely combine different components (shapes, materials, and motion constraints) into new solids within the plain-text input file, and implement new shapes and motion constrains easily. sdfibm is an efficient and robust tool for exploring complex fluid–solid interactions in a fully-resolved sense, and can generate data for closure models in upscaling procedures. Program summary Program title: sdfibm CPC Library link to program files: http://dx.doi.org/10.17632/hcvtddjngv.1 Licensing provisions: GNU General Public License 3 Programming language: C++ Nature of problem: Fluid–structure interaction and particle-laden multi-phase flow problems, with the structure/solid phase being rigid bodies. Examples range from classic flows passing stationary cylinder or sphere, to the sedimentation of a cluster of particles. Thanks to the fully-resolved direct numerical simulation, detail data of the flow field and particle motion are obtained as part of the solution, which can be used to analyze the dynamic process and to build coarse-grain models for industrial scale simulations. Solution method: The solution method can be divided into the fluid part and the solid part. For the fluid part, the Navier–Stokes equations are solved via the projection method. Because of the collocated arrangement of variables, a mesh face based flux field is used to enforce the divergence-free condition. The solid part follows Newtonian dynamics and is solved using linear multi-step method. The coupling of the two is via volume-average discrete forcing, which is an immersed boundary formulation suitable for rigid bodies. To find the forcing, the solid volume fraction at each fluid mesh cell is needed, which is calculated accurately on arbitrary unstructured meshes using signed distance field.

中文翻译：

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sdfibm：OpenFOAM 中基于有符号距离场的离散强迫浸入边界方法

摘要 在本文中，我们介绍了基于 OpenFOAM v6 并用 C++ 编写的开源浸入式边界代码 sdfibm 的算法和实现。浸入边界法（名称中的“ibm”）将速度场视为流体和固体速度的体积平均值，并应用体积平均离散力来解释流体-固体相互作用。固体形状的带符号距离场（名称中的“sdf”）表示，连同所提出的金字塔分解方法，允许准确计算由与任意非结构化流体网格重叠的固体产生的体积分数场。SDF 消除了实体和流体网格之间的相交测试，或实体形状的离散化和重新采样的需要。用户可以自由组合不同的组件（形状、材料、和运动约束）到纯文本输入文件中的新实体中，并轻松实现新的形状和运动约束。sdfibm 是一种有效且强大的工具，用于在完全解析的意义上探索复杂的流体-固体相互作用，并且可以为放大过程中的闭合模型生成数据。程序摘要 程序名称：sdfibm CPC 库程序文件链接：http://dx.doi.org/10.17632/hcvtddjngv.1 许可条款：GNU 通用公共许可证 3 编程语言：C++ 问题性质：流体-结构相互作用和粒子-负载多相流动问题，结构/固相是刚体。示例范围从通过静止圆柱体或球体的经典流动到粒子簇的沉降。由于完全解析的直接数值模拟，流场和粒子运动的详细数据作为解决方案的一部分获得，可用于分析动态过程并为工业规模模拟建立粗粒度模型。溶液法：溶液法可分为流体部分和固体部分。对于流体部分，通过投影法求解 Navier-Stokes 方程。由于变量的并置排列，基于网格面的通量场用于强制执行无发散条件。实体部分遵循牛顿动力学，并使用线性多步法求解。两者的耦合是通过体积平均离散力实现的，这是一种适用于刚体的浸入式边界公式。为了找到强迫，需要每个流体网格单元的固体体积分数，