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arXiv 2103.04521physics.flu-dyn
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笛卡尔网格上的浸没层法及其在不可压缩流中的应用

A method of immersed layers on Cartesian grids, with application to incompressible flows

Jeff D. Eldredge

摘要:

Peskin(J. Comput.物理、1977),以及衍生形式,诸如Taira和Colonius的投影法(J. Comput.物理、2007年),已被用于模拟流动物理问题的移动界面上的固定网格。然而,在它们的界面处理中,这些方法不区分一侧与另一侧,而是将运动约束应用于两侧,并且相关联的界面力是来自每一侧的贡献的不可分割的混合。在这项工作中,我们定义了一个离散的Heaviside函数,一个自然的伴侣熟悉的离散狄拉克δ函数(DDF),定义一个屏蔽版本的网格上的每个字段,在误差的DDF,需要的字段的预期值的接口的相应两侧。从这个基础上,我们开发离散算子和身份,是一致适用于任何表面几何。我们使用这些开发扩展形式的原型偏微分方程,包括泊松,对流扩散,不可压缩的Navier-Stokes方程,管理的离散掩蔽字段。这些方程包含了IBM中常见的强迫项,但也包含了一些附加项,这些附加项将场量的跳跃正则化到网格上,并使我们能够单独指定界面两侧场行为的约束。绘制这些条款之间的联系和层的潜力在椭圆问题,我们把它们统称为浸没层。我们演示了几个代表性的问题,包括二维不可压缩流动内的旋转圆柱体和外部的旋转广场的方法的应用。

英文摘要:

The immersed boundary method (IBM) of Peskin (J. Comput. Phys., 1977), and derived forms such as the projection method of Taira and Colonius (J. Comput. Phys., 2007), have been useful for simulating flow physics in problems with moving interfaces on stationary grids. However, in their interface treatment, these methods do not distinguish one side from the other, but rather, apply the motion constraint to both sides, and the associated interface force is an inseparable mix of contributions from each side. In this work, we define a discrete Heaviside function, a natural companion to the familiar discrete Dirac delta function (DDF), to define a masked version of each field on the grid which, to within the error of the DDF, takes the intended value of the field on the respective sides of the interface. From this foundation we develop discrete operators and identities that are uniformly applicable to any surface geometry. We use these to develop extended forms of prototypical partial differential equations, including Poisson, convection-diffusion, and incompressible Navier-Stokes, that govern the discrete masked fields. These equations contain the familiar forcing term of the IBM, but also additional terms that regularize the jumps in field quantities onto the grid and enable us to individually specify the constraints on field behavior on each side of the interface. Drawing the connection between these terms and the layer potentials in elliptic problems, we refer to them generically as immersed layers. We demonstrate the application of the method to several representative problems, including two-dimensional incompressible flows inside a rotating cylinder and external to a rotating square.

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