For a strictly inviscid barotropic flow with conservative body forces, the Helmholtz vorticity theorem shows that material or Lagrangian surfaces which are vortex surfaces at time t =0 remain so for t > 0. In this study, a systematic methodology is developed for constructing smooth scalar fields φ(x, y, z, t =0) for Taylor–Green and Kida– Pelz velocity fields, which, at t =0, satisfy ω · ∇φ=0. ...

Vortex methods for inviscid incompressible two-dimensional uid ow are usually based on blob approximations. This paper presents a vortex method in which the vorticity is approximated by a piecewise polynomial interpolant on a Delaunay triangulation of the vortices. An e cient reconstruction of the Delaunay triangulation at each step makes the method accurate for long times. The vertices of the ...

Sufficient conditions for the existence of quasi-pe~odic solutions of two different desingularized vortex models for 2-dimensional Euler flows are derived. One of these modds is the vortex blob model for the evolution of a periodic vortex sheet and the other is a second order elliptic moment model (DEMM) for the evolution of widely separated vortex regions. The method involves the identificatio...

Point vortex and vortex blob computations are used to investigate the evolution of the planar and the axisymmetric vortex sheet which initially induce ow past a cylinder and past a sphere respectively. In both cases the sheet develops a singularity at two points in the symmetry plane at a nite time. It rolls up at these points forming a vortex pair in the planar case and a vortex ring in the ax...

The separated flow around a rotating circular cylinder is investigated by the discrete vortex method combined with the boundary layer theory. The Keller Box method is used to solve the laminar boundary layer in order to determine the separation points on the upper and the lower sides of the rotating circular cylinder. The nascent vortices are then introduced near the separation points. A discre...

Numerical simulations of a driven elastic string in a quenched random potential at nite temperatures support the existence of glassy motion for suuciently weak driving forces. Avalanche-like string motion is observed in the transition region. The dynamics of an elastic string in a random medium provides an excellent model for the description of a variety of interesting phenomena|including uctua...

Explicit radius for nearly parallel vortex filaments in equilibrium 1 Geophysical research has focused on flows, such as ocean currents, as two dimensional. Two dimensional point or blob vortex models have the advantage of having a Hamilto-nian, whereas 3D vortex filament or tube systems do not necessarily have one, although they do have action functionals. On the other hand, certain classes of...

In this paper, we introduce a random particle blob method for the Keller-Segel equation (with dimension d ≥ 2) and establish a rigorous convergence analysis.

This paper presents a system to segment and track multiple body parts of interacting humans in the presence of mutual occlusion and shadow. The color image sequence is processed at three levels: pixel level, blob level, and object level. A Gaussian mixture model is used at the pixel level to train and classify individual pixel colors. Markov Random Field (MRF) framework is used at the blob leve...