Vortical structures like the Λ-vortex and ring-like vortex play a critical role in the boundary layer transition process. In this paper, the mechanisms of the formation of the vortical packets and their mutual interactions are studied by DNS. It is found that the shear layer instability is the key of the vortex generation. On the other hand, in the process of evolution of vortical packets, the ...

In this paper, we analyse by numerical simulations the nonlinear dynamics of the elliptic instability in the configurations of a single strained vortex and a system of two counter-rotating vortices. We show that although a weakly nonlinear regime associated with a limit cycle is possible, the nonlinear evolution far from the instability threshold is, in general, much more catastrophic for the v...

Vortex motion in ordered structures is analysed numerically in the frame of the 2D nonlinear Schrodinger equation. ̈ Ž . Analogies with superfluid dynamics are presented. It was found that coherent interaction of optical vortex solitons OVSs leads to vortex motion, which can be adequately described by the Kelvin law in superfluid dynamics for large offsets between the OVSs. Cancelation of motion...

The short wave instability on corotating vortex filaments is investigated. It is shown that the short wave instability always occurs on corotating vortex filaments of fixed core structure. Moreover, when the interfilament distance is smaller than or comparable to the core size, vortex filaments produce short wave unstable modes which lead to wild stretching and folding; when vortex filaments ar...

The vortex tube is an intriguing device that separates an incoming high-pressure fluid stream into a two low-pressure streams. Work interaction during the expansion process causes a temperature decrease in one of the two exit streams, while the other one experiences a temperature increase. The overall expansion process in a vortex tube therefore approaches isentropic rather than isenthalpic exp...

Regularized point-vortex simulations are presented for vortex sheet motion in planar and axisymmetric flow. The sheet forms a vortex pair in the planar case and a vortex ring in the axisymmetric case. Initially the sheet rolls up into a smooth spiral, but irregular small-scale features develop later in time: gaps and folds appear in the spiral core and a thin wake is shed behind the vortex ring...

Introduction: Characterization of turbulence phenomena in fluid transport systems is useful in understanding energy conservation, dissipation, and exchange. Vortices, structures exhibiting circular or swirling motion, are central in defining flow fields and flow structure. Formation of vortices and changes in their structure are determined by structural geometry of the system as well as other g...

In order to investigate continuous vortex dynamics based on a Lagrangian-like formulation, we develop a theoretical framework and a numerical method for computation of the evolution of a vortex-surface field (VSF) in viscous incompressible flows with simple topology and geometry. Equations describing the continuous, timewise evolution of a VSF from an existing VSF at an initial time are first r...

Because of the complexity of the flow field in a trailing vortex, prediction of tip vortex cavitation inception on a hydrofoil or a propeller still relies heavily on model tests and application of cavitation scaling. Experiments indicate that the major parameters influencing tip vortex cavitation inception are fluid viscosity (Reynolds number) and free stream nuclei (Weber number). A scaling me...

A coherent-vortex analysis is made of a computational solution for the free decay of homogeneous, Charney-isotropic geostrophic turbulence at large Reynolds number. The method of analysis is a vortex detection and measurement algorithm that we call a vortex census. The census demonstrates how, through non-conservative interactions among closely approaching vortices, the vortex population evolve...