Numerical Study on Entrance Length in Thermal Counterflow of Superfluid 4He
Numerical Study on Entrance Length in Thermal Counterflow of Superfluid 4He
复制标题
超流体4He热逆流入口长度的数值研究
DOI：
10.1007/s10909-019-02169-8
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发表时间：
2019
影响因子：
2
通讯作者：
Makoto Tsubota
中科院分区：
文献类型：
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作者：
Hiromichi Kobayashi;Satoshi Yui;Makoto Tsubota
对超流氦热逆流中的正常流体和超流氦的入口长度进行了三维数值模拟。这两种流体粗粒化使用Hall-Vinen-Bekharevich-Khalatnikov（HVBK）模型，并通过相互摩擦耦合。通过参数化互摩擦系数来考虑涡线密度，求解HVBK方程。在流向方向上，假设了一个均匀的相互摩擦参数。我们的模拟表明，从热端的正常流体的入口长度变得比一个单一的正常流体的入口长度更短，由于在热端附近的抛物线发展的超流的相互摩擦。随着相互摩擦的增加，入口长度减小。同样，超流从冷端进入的长度也受到冷端附近抛物线发展的正向流体流动所产生的相互摩擦力的影响。在不考虑入口效应的情况下，通过对超流湍流粘性系数和相互摩擦系数的参数化，讨论了尾翼压扁流的实现条件。
Three-dimensional numerical simulations in a square duct were conducted to investigate entrance lengths of normal fluid and superfluid flows in a thermal counterflow of superfluidHe. The two fluids were coarse-grained by using the Hall–Vinen–Bekharevich–Khalatnikov (HVBK) model and were coupled through mutual friction. We solved the HVBK equations by parameterizing the coefficient of the mutual friction to consider the vortex line density. A uniform mutual friction parameter was assumed in the streamwise direction. Our simulation showed that the entrance length of the normal fluid from a hot end becomes shorter than that of a single normal fluid due to the mutual friction with the parabolically developed superfluid flow near the hot end. As the mutual friction increases, the entrance length decreases. Same as that, the entrance length of the superfluid from a cold end is affected by the strength of the mutual friction due to the parabolically developed normal fluid flow near the cold end. Aside from the entrance effect, the realized condition of a tail-flattened flow is discussed by parameterizing the superfluid turbulent eddy viscosity and the mutual friction.