Both experimental and numerical studies of fluid motion indicate that initially localized regions of vorticity tend to evolve into isolated vortices and that these vortices then serve as organizing centers for the flow. In this paper we prove that in two dimensions localized regions of vorticity do evolve toward a vortex. More precisely we prove that any solution of the two-dimensional Navier-S...

in this paper, synoptic patterns associated with maximum precipitation over the khorasan region, between 1985-2000 with the computation of some forcing functions are studied and classified into three types. type a: consists of the anticyclones that move from the scandinavian peninsula and central-europe in an east and south-east direction during cold seasons, with relatively high speed and cold...

Vortical flows in shallow water interact with long surface waves by virtue of the nonlinear terms of the fluid equations. Analytical formulae are derived that quantify the spontaneous generation of such waves by unsteady vorticity as well as the scattering of surface waves by vorticity. In a first Born approximation the radiated surface elevation is linearly related to the Fourier transform of ...

Acoustic field generated by a single vortex approaching a hydrofoil is studied. A combined vortex/RANS simulation for the near–field unsteady vorticity is developed to include effects from RANS Reynolds stresses. The far-field acoustics is calculated using a vortex sound formula with the near-field vorticity as the source. The results show that at a higher incident angle when the RANS shows a s...

We investigate feature detection schemes used to guide appropriate mesh resolution for CFD calculations with adaptive mesh refinement (AMR). Methods based on eigenvalues of the velocity gradient, difference between vorticity and strain rate magnitudes, and eigenvalues of the vorticity vector are investigated and compared to traditional vorticity-based detection schemes such as the Q-criterion. ...

We analyze the dynamics of a perfectly flexible string with a constant length and a vanishing inner friction. The local angular velocity of line elements in this seemingly simple mechanical system is shown to have many mathematical and physical properties in common with vorticity in the three-dimensional incompressible Euler equation. It is demonstrated that initially smooth vorticity fields lo...

The nonlinear Schrödinger (NLS) equation describing the propagation of weakly rotational wave packets in an infinitely deep fluid in Lagrangian coordinates has been derived. The vorticity is assumed to be an arbitrary function of Lagrangian coordinates and quadratic in the small parameter proportional to the wave steepness. The vorticity effects manifest themselves in a shift of the wave number...

In this paper, the differential quadrature method is applied to simulate natural convection in an inclined cubic cavity using velocity-vorticity formulation. The numerical capability of the present algorithm is demonstrated by application to natural convection in an inclined cubic cavity. The velocity Poisson equations, the vorticity transport equations and the energy equation are all solved as...

Large fluctuations in complex systems from earthquakes to financial markets, though infrequent, are particularly important because of their disproportionate impact. Our ability to forecast them is quite poor at present. Large fluctuations occur also in intermittent features of turbulent flows. Some dynamical understanding of these features is possible because the governing equations are known a...

introduction the dynamic state index (dsi) is being introduced on the basis of a newly developed theory termed the energy-vorticity theory (evt). as a weather index, the dsi can describe the temporal sequence and intensity of areas of high and low pressure; but as a climate index, it can also diagnose climate change based on the variation in solar radiation or the influences of friction. in phy...