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arXiv 1806.09307physics.flu-dyn
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不同表面时间尺度下毛状表面与turbulence的相互作用

Interaction between hairy surfaces and turbulence for different surface time scales

Johan Sundin, Shervin Bagheri

摘要:

具有丝状结构的表面在自然界中以许多不同的尺度普遍存在,从森林到器官中的微米级纤毛。毛状表面是弹性的和多孔的,人们还没有完全理解它们如何改变壁附近的湍流。本文在$Re_τ\approx 180$的湍流槽道流结构中对毛状表面与湍流的相互作用进行了数值研究。我们表明,一个给定的几何形状的丝状床可以修改湍流非常不同的表面,这是由弹性和质量的细丝的共振频率。具有低于湍流壁剪切应力的主频率成分的共振频率的细丝符合缓慢行进的细长条纹结构,因为它们太慢而不能适应较高频率的流体力。另一方面,由刚性和低质量细丝组成的床具有高共振频率,并显示出渗透率增加的局部区域,这导致大夹带和阻力的大幅增加。

英文摘要:

Surfaces with filamentous structures are ubiquitous in nature on many different scales, ranging from forests to micrometer-sized cilia in organs. Hairy surfaces are elastic and porous, and it is not fully understood how they modify turbulence near a wall. The interaction between hairy surfaces and turbulent flows is here investigated numerically in a turbulent channel flow configuration at $Re_τ\approx 180$. We show that a filamentous bed of a given geometry can modify a turbulent flow very differently depending on the resonance frequency of the surface, which is determined by elasticity and mass of the filaments. Filaments having resonance frequencies lower than the main frequency content of the turbulent wall-shear stress conform to slowly traveling elongated streaky structures, since they are too slow to adapt to fluid forces of higher frequencies. On the other hand, a bed consisting of stiff and low-mass filaments has a high resonance frequency and shows local regions of increased permeability, which results in large entrainment and a vast increase in drag.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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