arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2108.01786physics.flu-dyncs.NAmath-phmath.APmath.MPmath.NA
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有地形和障碍物背景流的水波数值算法

Numerical Algorithms for Water Waves with Background Flow over Obstacles and Topography

David M. Ambrose, Roberto Camassa, Jeremy L. Marzuola, Richard M. McLaughlin, Quentin Robinson, Jon Wilkening

摘要:

我们提出了两个准确和有效的算法求解不可压缩,无旋欧拉方程的自由表面在二维背景流周期性,多连通的流体域,包括固定的障碍物和可变的底部地形。一种方法是制定的表面速度潜力,而其他的演变涡面强度。这两种方法采用层电位的形式周期柯西积分计算的正常速度的自由表面,与任意参数化的自由表面和边界兼容,并允许循环周围的每个障碍物,这导致多值速度势,但单值流函数。我们证明了由此产生的第二类Fredholm积分方程是可逆的,可能经过物理动机的有限秩校正。在一个角度弧长设置,我们展示了如何避免与空间周期性不兼容的曲线重建错误。我们使用所提出的方法来研究重力毛细波产生的流动周围的几个椭圆形障碍物以上的平坦或可变的底部边界。在每种情况下,自由表面最终在飞溅奇点中自相交或与边界碰撞。我们还展示了如何评估整个流体的速度和压力与频谱精度,包括附近的自由表面和固体边界。为了评估时间演化的准确性,我们监测能量守恒和傅立叶模式的衰减,并比较两种方法的数值结果。我们实现了几个求解器的离散线性系统,并比较它们的性能。最快的方法采用图形处理单元(GPU)来构造矩阵并执行广义最小残差方法(GMRES)的迭代。

英文摘要:

We present two accurate and efficient algorithms for solving the incompressible, irrotational Euler equations with a free surface in two dimensions with background flow over a periodic, multiply-connected fluid domain that includes stationary obstacles and variable bottom topography. One approach is formulated in terms of the surface velocity potential while the other evolves the vortex sheet strength. Both methods employ layer potentials in the form of periodized Cauchy integrals to compute the normal velocity of the free surface, are compatible with arbitrary parameterizations of the free surface and boundaries, and allow for circulation around each obstacle, which leads to multiple-valued velocity potentials but single-valued stream functions. We prove that the resulting second-kind Fredholm integral equations are invertible, possibly after a physically motivated finite-rank correction. In an angle-arclength setting, we show how to avoid curve reconstruction errors that are incompatible with spatial periodicity. We use the proposed methods to study gravity-capillary waves generated by flow around several elliptical obstacles above a flat or variable bottom boundary. In each case, the free surface eventually self-intersects in a splash singularity or collides with a boundary. We also show how to evaluate the velocity and pressure with spectral accuracy throughout the fluid, including near the free surface and solid boundaries. To assess the accuracy of the time evolution, we monitor energy conservation and the decay of Fourier modes and compare the numerical results of the two methods to each other. We implement several solvers for the discretized linear systems and compare their performance. The fastest approach employs a graphics processing unit (GPU) to construct the matrices and carry out iterations of the generalized minimal residual method (GMRES).

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