# Limit Points of Empirical Distributions of Vorticies with Small Viscosity

Chapter

## Abstract

Let v(t,z) (z=(x,y)εR where \( \text{G}\left( \text{z} \right)=-{{\left( 2\text{ }\!\!\pi\!\!\text{ } \right)}^{-1}}\text{ log}\left| \text{z} \right|,* \) denotes convolution, \( \Delta =\left( \frac{\partial }{\partial \text{x}},\frac{\partial }{\partial \text{y}} \right) \) and \( {{\Delta }^{\bot }}=\left( \frac{\partial }{\partial \text{y}},-\frac{\partial }{\partial \text{x}} \right) \). Here

^{2}) be the vorticity of an incompressible and viscous two dimensional fluid, under the action of an external conservative field. Then v is described by the following evolution equation$$ {{\partial }_{\text{t}}}\text{v+}\left( \text{u}\centerdot \Delta \right)\text{v}-v\Delta \text{v=0, u}\left( \text{t},\text{z} \right)=\left( \Delta {}^{\bot }\text{G} \right)*\text{v}\left( \text{t},\text{z} \right), $$

(0.1)

*v*> 0 denotes the viscosity constant. As far as strong solutions concerns, (0,1) is equivalent to the Navier-Stokes equation. In fact, u(t,z) turns to be the velocity field described by the Navier-Stokes equation. Conversely we can get v from u as v = curl u. Since the two dimensional Navier-Stokes equation is an equation of a vector valued function, a probabilistic treatment is not easy, while the vorticity equation (0.1) is nothing but a McKean’s type non-linear equation (see [3]. Such an observation for the two dimensional Navier-Stokes equation was made by Marchioro-Pulvirenti in [2].## Keywords

Vorticity Equation Vortex Method Small Viscosity Homogenous Boltzmann Equation Dimensional Fluid
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Springer-Verlag New York Inc. 1987