A technique of mechanical airflow sensing based on coupling to a film of fluid smectic liquid crystals is presented. A gas jet confined to a narrow channel induces flow in a continuous, freely suspended film with racetrack geometry, whose velocity field is then mapped using video microscopy and particle tracking techniques. Because the nanofilm has so little mass compared to the air, its velocity provides a direct readout of the velocity profile of the gas in the channel. This method of flow measurement offers several advantages over conventional mechanical flow meters: It has linear sensitivity, and so, it can operate at low flows, and the energy lost due to the measurement is negligible.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.