Mathematical modeling of rivulet flow driven by variable gravity and gas flow in a minichannel

Rivulet flows are a special type of thin film flows with a bounded width. The use of rivulet flows is very perspective in various types of process equipment such as evaporators. The flow dynamics in rivulets has some peculiarities, the investigation of which allows understanding the gist of possible mechanism of enhancement of heat transfer. In the present work a mathematical model for the rivulet flow in conditions of a variable gravity has been elaborated. The liquid flow takes place in a slot between two plates and is caused by a co-current gas flow. The numerical calculations of the flow parameters depending from the gravity forces have been made. The analytical formula for connection of the main rivulet parameters (width, contact angle, liquid flow rate ...) in a linearized approach has been derived. The comparison of numerical results with experimental data obtained during 44 Parabolic Flights campaign of the European Space Agency has been carried out. Liquid film of FC-72 driven by the Nitrogen gas has been studied in experiments. Force balance is changed during a parabolic flight and due to surface tension effect the liquid film in a horizontal minichannel 40 mm width became a flattened rivulet 9 mm width at microgravity.