It is shown: 1) that in two-dimensional, incompressible, viscous flows the vorticity-area distribution evolves according to an advection-diffusion equation with a negative, time dependent diffusion coefficient and 2) how to use the vorticity-streamfunction relations, i.e., the so-called scatter-plots, of the quasi-stationary coherent structures in order to quantify the experimentally observed c...

For the past several years, there has been a lot of work in modelling complex simulations pertaining to motion of gases. In the work of [Fedkiw et al., 2001], a new approach to numerically simulate smoke was developed which incorporates the model proposed by Steinhoff and Underhill [Steinhoff and Underhill, 1994] known as “vorticity confinement”. Passive advection of smoke particles is consider...

The focus of this work is on a two-dimensional stochastic vorticity equation for an incompressible homogeneous viscous fluid. We consider a signed measure-valued stochastic partial differential equation for a vorticity process based on the Skorohod–Ito evolution of a system of N randomly moving point vortices. A nonlinear filtering problem associated with the evolution of the vorticity is consi...

A stability condition is provided for a class of vorticity boundary formulas used with the second order finite-difference numerical scheme for the vorticity-stream function formulation of the unsteady incompressible Navier-Stokes equations. These local vorticity boundary formulas are derived using the no-slip boundary condition for the velocity. A new form of these long-stencil formulas is need...

Rivers empty into oceans and lakes as turbulent sediment-laden jets, which can be characterized by a Gaussian horizontal velocity profile that spreads and decays downstream because of shearing and lateral mixing at the jet margins. Recent experiments demonstrate that this velocity field controls river-mouth sedimentation patterns. In nature, diffuse jets are associated with mouth bar deposition...

The downstream evolution of the vorticity field in the vicinity of hairpinshaped regions of rotational motion appearing in the transitioning boundary layer is examined. It is shown that the dynamics of hairpins is inseparable from that of the non-rotational vorticity out of which they develop in a self-reinforcing process of ejection and reorientation. Widening the concept of structure to inclu...

which implies that the topology of the vorticity vector field must be very simple. Even local existence of the Clebsch representation is only guaranteed at points where the vorticity does not vanish. It has been shown (Graham-Henyey [17]) that in general (1.3) can not hold around a point with zero vorticity. For more discussion on the properties of classical Clebsch variables and its various ge...

An initial value approach is used to examine the dynamics of perturbations introduced into a vortex under strain. Both the basic vortex considered and the perturbations are taken as fully three-dimensional. An explicit solution for the time evolution of the vorticity perturbations is given for arbitrary initial vorticity. Analytical solutions for the resulting velocity components are found when...

Thewake flow behind two yawed side-by-sidecircular cylinders is investigated using athree-dimensional vorticity probe. Four yaw angles (α), namely, 0°, 15°, 30° and 45° and twocylinder spacing ratios T of 1.7 and 3.0 were tested. For T = 3.0, there exist two vortex streets and the cylinders behave as independent and isolated ones. The maximum contour value of the coherent streamwise vorticity *...

This study examines the extent to which sea level variations at periods less than a year and spatial scales greater than 1000 km can be described by the wind-driven linear barotropic vorticity dynamics. The TOPEX/POSEIDON altimetric observations of sea level and the wind products of the National Meteorological Center are used as the database for the study. Each term of the linear bamtropic vort...