Abstract
An investigation of topological features of homogeneous isotropic turbulence with an inverse energy cascade is performed by using a direct numerical simulation. The inverse energy cascade is induced by reversing the velocity field (i.e., under the transformation from ui to −ui) of a freely decaying isotropic turbulence. In the backward energy transfer process, the joint probability density function (PDF) of Q and R exhibits a novel shape, which seems to be symmetric with the well-known teardrop shape about the Q-axis (Q and R are the second and third invariants of the velocity gradients tensor, respectively). The predominance of the top-right (R > 0 and Q > 0) and the bottom-left (R < 0 and Q < 0) quadrants is observed in the backward energy transfer process. This observation is different from that of the forward energy cascade, in which the top-left (R < 0 and Q > 0) and the bottom-right (R > 0 and Q < 0) quadrants are dominant. The unexpected shape of the joint PDF of Q and R indicates that the turbulence with an inverse energy cascade is dominated by vortex compression and tube-like structures. The PDF of the intermediate eigenvalue of the strain-rate tensor in the inverse energy cascade is negatively skewed, which is opposite to the universal feature of the forward energy cascade. Nevertheless, the preferential alignment of vorticity with the intermediate eigenvector is rather robust, no matter whether the direction of the energy transfer is forward or backward. In addition, it is universal that the vorticity is mostly perpendicular to the eigenvector, which corresponds to a strain-rate eigenvalue with the maximum absolute value among the three eigenvalues. Since the velocity gradient invariants are closely related to the local flow topology, the numerical results reported in this work are expected to shed light on the intrinsic dynamics and mechanisms of inverse energy cascade.
Funder
National Natural Science Foundation of China
China Postdoctoral Science Foundation
Science and Technology Innovation Projects of Shanxi Provincial Universities
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering
Cited by
4 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献