|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)
The disintegration of a radially thinning liquid sheet into drops, which is induced directly by the transition from laminar to turbulent flow, is investigated.
The liquid sheet in the present experiment is generated as follows ; a radial liquid film flow is formed by a tap water issue from a thin cylindrical gap, which is constructed by the end of a circular pipe and the flat surface of a circular plate, to suppress the turbulence of the flow to the utmost. The liquid film flows radially outward on the plate, detaching from the peripheral edge of the plate, and then the liquid flows outward as a radially thinning liquid sheet in still air.
Although the liquid aheet is laminar with a smooth liquid surface under the low Reynolds number flow, the transition of the thin liquid sheet begins to occur at a location of several millimeters downstream of the plate edge at high Reynolds number flow, being attributable to the velocity profile having an inflection point dueto the removal of the shear
stress on the wall. The intensity of the turbulence increases with the Reynolds number, and the turbulence begins to sporadically perforate the liquid sheet at a immediately downstream location from the plate edge. A further increase in the number of perforation with the discharge Reynolds number causes to decreasing in sizes of webs and strands, and finally, the configuration of the web of strand does not appear in the liquid sheet and the transition results in the sudden breakup of the sheetinto drolets and clumps. The sizes of droplets are several tens micrometers and those of clumps are several hurdreds to some thousands micrometers.
Although the quality of the disintegration rises further with the stagnant pressure, there are two limitations. The one is that the liquid film flow at the plate edge must have a fully developed velocity distribution, and the other is that no transition occurs in the flow on the plate. Flow conditions for the effective disintegration directly due to the transition of the liquid sheet are also clarified.