DATE:

Friday, October 18, 2019

TIME:

3:30 PM

LOCATION:

GMCS-314

SPEAKER:

Oscar Fuentes, Ph.D, Ensenada Center for Research and Higher Education, Department of Physical Oceanography.

ABSTRACT:

Joukowsky (1912) deduced that a system of equal, coaxial, symmetrically-located
helical vortices advance and rotate steadily while preserving their shape and
relative position if they are sufficiently thin and move in an unbounded, inviscid,
incompressible fluid. Velasco Fuentes (2018) obtained the linear and angular
velocities corresponding to this motion and, by analyzing the flow topology in a
reference system that moves with the vortices, determined the capacity of the
vortices to transport fluid. In this seminar I will discuss the vortex evolution
when the thinness condition is not satisfied and the advection of particles when the
symmetry condition is not satisfied. To study the effect of core size we solved the
Helmholtz vorticity equation in a triple-periodic domain with a vortex-in-cell
method. We found that a pair of thick vortices exhibit two main regimes of behavior:
Large-pitch vortices merge to form a single cylindrical column with mainly axial
vorticity whereas small-pitch vortices merge to form a single cylindrical
shell with mainly azimuthal vorticity. To study the effect of asymmetry we computed
the vortex motion and particle advection using the Rosenhead-Moore
approximation to the Biot-Savart law. We found that a pair of vortices perform a
leapfrogging motion, keeping a helical shape with periodically varying radius
and pitch, and particle trajectories become chaotic.

HOST:

Chris Curtis, Department of Mathematics and Statistics

DOWNLOAD:

PDF File