发表机构
Politecnico di Milano（米兰理工大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过改进的纳维-斯托克斯系统直接数值模拟，发现涡量放大是维持经典能量级联和反常耗散的必要条件，而涡量倾斜单独足以维持多重分形间歇性。
AI 中文摘要
通过改进的纳维-斯托克斯系统的直接数值模拟，研究了三维均匀各向同性湍流中涡量放大（VA）和涡量倾斜（VT）的不同动力学作用。通过选择性地抑制VA而保留VT，我们证明VA引起的梯度放大是维持经典正向能量级联的严格必要条件。逐步抑制VA会削弱小尺度速度梯度，严重耗竭极端涨落，并完全消除经典的能量耗散反常，导致归一化能量耗散按$Re_\lambda^{-1}$衰减。在完全抑制VA的极限下，涡量拟能成为相关的无粘不变量。逐尺度预算分析证实，动力学转变为纯正向涡量拟能级联，其特征是反常涡量耗散和稳健的$E(k) \sim k^{-3}$中间能量谱。我们验证了这些渐近标度极限——包括涡量反常耗散的$Re_\lambda^{-1/2}$有限雷诺数修正——是VA抑制动力学的普适性质，与大规模强迫是螺旋还是非螺旋无关。值得注意的是，尽管速度场被平滑且能量耗散反常被消除，反常结构标度和宽多重分形谱仍然存在。这些结果揭示了一个基本的机制分离：虽然VA负责放大强烈的局部涨落，但仅由VT进行的几何重组在机械上足以维持多重分形间歇性。
英文摘要
The distinct dynamical roles of vorticity amplification (VA) and vortex tilting (VT) in three-dimensional homogeneous isotropic turbulence are investigated using direct numerical simulations of a modified Navier--Stokes system. By selectively suppressing VA while retaining VT, we demonstrate that gradient amplification by VA is strictly required to sustain the classical forward energy cascade. Progressively suppressing VA weakens small-scale velocity gradients, heavily depletes extreme fluctuations, and entirely eliminates the classical energy dissipative anomaly, causing the normalized energy dissipation to decay as $Re_λ^{-1}$. In the limit of complete VA suppression, enstrophy emerges as the relevant inviscid invariant. Scale-by-scale budget analyses confirm that the dynamics transition to a purely forward enstrophy cascade, characterized by an anomalous enstrophy dissipation and a robust $E(k) \sim k^{-3}$ intermediate energy spectrum. We verify that these asymptotic scaling limits---including a $Re_λ^{-1/2}$ finite-Reynolds-number correction for the enstrophy anomalous dissipation---are universal properties of the VA-suppressed dynamics, independent of whether the large-scale forcing is helical or non-helical. Remarkably, despite the smoothing of the velocity field and the elimination of the energy dissipative anomaly, anomalous structural scaling and a broad multifractal spectrum persist. These results reveal a fundamental mechanistic separation: while VA is responsible for amplifying intense localized fluctuations, geometric reorganization by VT alone is mechanically sufficient to sustain multifractal intermittency.
