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arXiv 1603.02306physics.flu-dynphysics.comp-ph
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用浸入边界法精确计算表面应力和力

Accurate computation of surface stresses and forces with immersed boundary methods

Andres Goza, Sebastian Liska, Benjamin Morley, Tim Colonius

摘要:

许多浸入边界法求解表面应力,这些表面应力将速度边界条件施加在浸入体上。这些表面应力可能包含寄生振荡,使它们不适合代表身体上的物理表面应力。此外,这些不准确的应力往往导致非物理振荡的历史中的综合表面力,如升力系数。虽然表面应力和力的误差不一定会影响速度场的收敛,但特别是在流体-结构相互作用问题中,希望在表面上获得光滑和收敛的应力分布。为此,我们表明,方程的表面应力是一个积分方程的第一类,其不适定性是源的虚假振荡的应力。我们还表明,足够光滑的δ函数,振荡可以被过滤掉,以获得物理上准确的表面应力。滤波作为后处理过程应用,使得速度场的收敛不受影响。我们通过计算收敛到几个测试问题的物理应力和力的应力和力来证明该方法的有效性。

英文摘要:

Many immersed boundary methods solve for surface stresses that impose the velocity boundary conditions on an immersed body. These surface stresses may contain spurious oscillations that make them ill-suited for representing the physical surface stresses on the body. Moreover, these inaccurate stresses often lead to unphysical oscillations in the history of integrated surface forces such as the coefficient of lift. While the errors in the surface stresses and forces do not necessarily affect the convergence of the velocity field, it is desirable, especially in fluid-structure interaction problems, to obtain smooth and convergent stress distributions on the surface. To this end, we show that the equation for the surface stresses is an integral equation of the first kind whose ill-posedness is the source of spurious oscillations in the stresses. We also demonstrate that for sufficiently smooth delta functions, the oscillations may be filtered out to obtain physically accurate surface stresses. The filtering is applied as a post-processing procedure, so that the convergence of the velocity field is unaffected. We demonstrate the efficacy of the method by computing stresses and forces that converge to the physical stresses and forces for several test problems.

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