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Coarse-grained pressure dynamics in superfluid turbulence
Physical Review Fluids ( IF 2.5 ) Pub Date : 
Jason Laurie and Andrew W. Baggaley

Quantum mechanics places significant restrictions on the hydrodynamics of superfluid flows. Despite this it has been observed that turbulence in superfluids can, in a statistical sense, share many of the properties of its classical brethren; coherent bundles of superfluid vortices are often invoked as an important feature leading to this quasi-classical behaviour. A recent experimental study~ inferred the presence of these bundles through intermittency in the pressure field, however direct visualization of the quantized vortices to corroborate this finding was not possible. In this work, we performed detailed numerical simulations of superfluid turbulence at the level of individual quantized vortices through the vortex filament model. Through course-graining of the turbulent fields, we find compelling evidence supporting the conclusions of Ref.~ at low temperature. Moreover, elementary simulations of an isolated bundle show that the number of vortices inside a bundle can be directly inferred from the magnitude of the pressure dip, with good theoretical agreement derived from the HVBK equations. Full simulations of superfluid turbulence show strong spatial correlations between course-grained vorticity and low pressure regions, with intermittent vortex bundles appearing as deviations from the underlying Maxwellian (vorticity) and Gaussian (pressure) distributions. Finally, simulations of a decaying random tangle in an ultra-quantum regime show a unique fingerprint in the evolution of the pressure distribution, which we argue can be fully understood using the HVBK framework.

中文翻译:

超流体湍流中的粗粒度压力动力学

量子力学极大地限制了超流体流动的流体动力学。尽管如此,从统计意义上讲,已经观察到超流体中的湍流可以共享其经典弟兄的许多特性。超流体涡旋的相干束通常被称为导致这种准经典行为的重要特征。最近的一项实验研究通过压力场的间断性推断了这些束的存在,但是无法直接可视化量化的涡旋来证实这一发现。在这项工作中,我们通过涡流丝模型在单个量化涡水平上进行了超流体湍流的详细数值模拟。通过对湍流场进行过程细化,我们发现了有力的证据支持Ref。的结论。〜低温。此外,对孤立束的基本模拟表明,可以从压降的大小直接推断束中的涡旋数,并且可以从HVBK方程得出良好的理论一致性。对超流体湍流的完整模拟显示出过程颗粒状的涡度与低压区域之间存在很强的空间相关性,间歇性的涡旋束表现为与基础Maxwellian(涡度)和Gaussian(压力)分布的偏差。最后,在超量子状态下衰减随机缠结的模拟显示了压力分布演变过程中的唯一指纹,我们认为可以使用HVBK框架完全理解该指纹。隔离管束的基本模拟显示,可以从压降的大小直接推断出管束内的涡旋数,并且从HVBK方程式可以得出良好的理论一致性。对超流体湍流的完整模拟显示出过程颗粒状的涡度与低压区域之间存在很强的空间相关性,间歇性的涡旋束表现为与基础Maxwellian(涡度)和Gaussian(压力)分布的偏差。最后,在超量子状态下衰减随机缠结的模拟显示了压力分布演变过程中的唯一指纹,我们认为可以使用HVBK框架完全理解该指纹。隔离管束的基本模拟显示,可以从压降的大小直接推断出管束内的涡旋数,并且从HVBK方程式可以得出良好的理论一致性。对超流体湍流的完整模拟显示出过程颗粒状的涡度与低压区域之间存在很强的空间相关性,间歇性的涡旋束表现为与基础Maxwellian(涡度)和Gaussian(压力)分布的偏差。最后,在超量子状态下衰减随机缠结的模拟显示了压力分布演变过程中的唯一指纹,我们认为可以使用HVBK框架完全理解该指纹。对超流体湍流的完整模拟显示出过程颗粒状的涡度与低压区域之间存在很强的空间相关性,间歇性涡旋束表现为与基础麦克斯韦(涡度)和高斯(压力)分布的偏差。最后,在超量子状态下衰减随机缠结的模拟显示了压力分布演变过程中的唯一指纹,我们认为可以使用HVBK框架完全理解该指纹。对超流体湍流的完整模拟显示出过程颗粒状的涡度与低压区域之间存在很强的空间相关性,间歇性涡旋束表现为与基础麦克斯韦(涡度)和高斯(压力)分布的偏差。最后,在超量子状态下衰减随机缠结的仿真显示了压力分布演变过程中的唯一指纹,我们认为可以使用HVBK框架完全理解该指纹。
更新日期:2020-01-10
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