  Two dimensional (2D) laminar jet-----a stream of fluid that projected into a
surrounding medium with the flow confined in 2D-----has both theoretical and
experimental significance. We carried out 2D laminar jet experiments in freely
suspended liquid crystal films (FSLCFs) of nanometers thick and centimeters in
size, in which individual molecules are confined to single layers thus enable
film flows with two degrees of freedom. The experimental observations are found
in good agreement with the classic 2D laminar jet theory of ideal cases that
assume no external coupling effects, even in fact there exist strong coupling
force from the ambient air. We further investigated this air coupling effect in
computer simulations, with the results indicated air has little influence on
the velocity maps of flow near the nozzle. This astonishing results could be
intuitively understood by considering 2D incompressibility of the films. This
experiment, together with a series of our previous experiments, show for a wide
range of Reynolds number, FSLCFs are excellent testing beds for 2D
hydrodynamics.
