Advection Maps for Closed Flows

a

0.3

x

0

1

y

0

1

n

300

Advection refers to the variation of a scalar field, induced by the effects of a superposed vector field, for example, the transport of pollutants to a river. A simple periodically repeating model of sinusoidal shear in a square region of size

L

is considered, assuming velocities with inversion symmetry.