Strain-resolved analysis of energy dissipation mechanisms in single-cell tornado-like vortices

Energy dissipation is crucial in fluid dynamics, especially in swirl flow systems known for their high energy intensity. Their flow behavior is widely studied, both as natural phenomena and in industrial applications. However, its mechanism in terms of energy is not investigated in sufficient depth. In this study, a numerical model of tornado-like vortices is developed using a self-constructed simulator and validated with high-precision experimental data. An energy loss model is employed to visualize energy dissipation and analyze its distribution and underlying mechanisms.

The results show that energy dissipation is primarily concentrated in the lower vortex core, with a viscous-to-turbulent dissipation ratio of 9:16. In particular, energy dissipation is closely related to fluid strain induced by stretching and shear deformations. During vortex formation, flow-induced traction and flow redirection due to centrifugal effects enhance velocity gradients, thereby increasing stretching deformation and energy dissipation. Moreover, horizontal shear deformation, driven by tangential velocity gradients in the vortex core, and vertical shear deformation arising from velocity gradients at the inner-outer vortex boundary, further intensify energy dissipation. Additionally, vortex eccentricity, a feature of spatial instability, results in uneven velocity gradient distribution, exacerbating dissipation. These findings provide novel insights into the energy dissipation mechanisms of tornado-like vortices and deepen the understanding of vortex dynamics.