Scale-to-scale energy and enstrophy transport in two-dimensional Rayleigh–Taylor turbulence
Scale-to-scale energy and enstrophy transport in two-dimensional Rayleigh–Taylor turbulence
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DOI：
10.1017/jfm.2015.673
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发表时间：
2015-12
影响因子：
3.7
通讯作者：
Quan Zhou;Yongxiang Huang;Zhiming Lu;Yu-lu Liu;R. Ni
中科院分区：
文献类型：
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作者：
Quan Zhou;Yongxiang Huang;Zhiming Lu;Yu-lu Liu;R. Ni
我们应用最近开发的过滤方法，即过滤空间技术（FST），来研究二维（2D）瑞利-泰勒（RT）湍流中动能、热能和熵的尺度传递。尽管由于浮力，二维 RT 系统中能量级联的标度定律遵循 Bolgiano-Obukhov (BO59) 情景，但平均而言，仍然发现动能通过逆级联动态转移到大尺度，而平均热能和平均熵都通过正向级联向小尺度移动。特别是，存在一个合理扩展的范围，在该范围内，热能的传递速率与尺度无关，并且在不同时间等于相应的热耗散速率。该范围的作用类似于均匀和各向同性湍流中动能的惯性范围。我们的结果进一步表明，在小尺度上，三个瞬时局部通量的波动是高度不对称分布的，并且任何两个通量之间都存在很强的相关性。这些小尺度特征是流体界面处具有陡峭温度梯度的流体混合和消散的特征。
We apply a recently developed filtering approach, i.e. filter-space technique (FST), to study the scale-to-scale transport of kinetic energy, thermal energy, and enstrophy in two-dimensional (2D) Rayleigh–Taylor (RT) turbulence. Although the scaling laws of the energy cascades in 2D RT systems follow the Bolgiano–Obukhov (BO59) scenario due to buoyancy forces, the kinetic energy is still found to be, on average, dynamically transferred to large scales by an inverse cascade, while both the mean thermal energy and the mean enstrophy move towards small scales by forward cascades. In particular, there is a reasonably extended range over which the transfer rate of thermal energy is scale-independent and equals the corresponding thermal dissipation rate at different times. This range functions similarly to the inertial range for the kinetic energy in the homogeneous and isotropic turbulence. Our results further show that at small scales the fluctuations of the three instantaneous local fluxes are highly asymmetrically distributed and there is a strong correlation between any two fluxes. These small-scale features are signatures of the mixing and dissipation of fluids with steep temperature gradients at the fluid interfaces.