Spandan Vamsi, Putt Daniel, Ostilla-Mónico Rodolfo, Lee Alpha A
Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Department of Mechanical Engineering, University of Houston, TX 77004, USA.
Sci Adv. 2020 Apr 3;6(14):eaba0461. doi: 10.1126/sciadv.aba0461. eCollection 2020 Apr.
Understanding force generation in nonequilibrium systems is a notable challenge in statistical physics. We uncover a fluctuation-induced force between two plates immersed in homogeneous isotropic turbulence using direct numerical simulations. The force is a nonmonotonic function of plate separation. The mechanism of force generation reveals an intriguing analogy with fluctuation-induced forces: In a fluid, energy and vorticity are localized in regions of defined length scales. When varying the distance between the plates, we exclude energy structures modifying the overall pressure on the plates. At intermediate plate distances, the intense vorticity structures (worms) are forced to interact in close vicinity between the plates. This interaction affects the pressure in the slit and the force between the plates. The combination of these two effects causes a nonmonotonic attractive force with a complex Reynolds number dependence. Our study sheds light on how length scale-dependent distributions of energy and high-intensity vortex structures determine Casimir forces.
理解非平衡系统中的力产生是统计物理学中的一个显著挑战。我们通过直接数值模拟揭示了浸没在均匀各向同性湍流中的两块平板之间的涨落诱导力。该力是平板间距的非单调函数。力产生的机制揭示了与涨落诱导力的有趣类比：在流体中，能量和涡度局域在具有确定长度尺度的区域。当改变平板之间的距离时，我们排除了改变平板上总压力的能量结构。在中间平板间距处，强烈的涡度结构（涡旋条）被迫在平板之间的近距离相互作用。这种相互作用影响狭缝中的压力和平板之间的力。这两种效应的组合导致了具有复杂雷诺数依赖性的非单调吸引力。我们的研究揭示了能量和高强度涡旋结构的长度尺度依赖性分布如何决定卡西米尔力。
