Experimental study of wave occlusion on falling films in a vertical pipe

Experiments were conducted to study wave occlusion on falling films in a ve rtical pipe with aqueous solutions of glycerine with viscosities from 0.022 to 1.25 kg/(m.s). Pipe diameters were varied from 0.00635 to 0.015875 m. F or each case, the critical liquid flow rate was determined at which the fre e falling wavy annular flow transforms into slug flow due to wave occlusion . The experimental results are correlated in terms of the liquid Reynolds n umber at occlusion (Re-LS = 4 q/pi nu D) and two dimensionless groups influ encing the transition: the Kapitza number Ka = sigma/[(nu g)(1/3)mu], and t he Bond number Bo = rho gD(2)/sigma. The annular-slug transition correlatio n was Re-LS = 0.062 Ka(4/3)Bo(2/3) and valid in the range 0.1 < Re-LS < 200 , 0.2 < Ka < 55 and 7 < Bo < 50. Experimental results were compared to rela ted published results, and the experimental correlation is explained qualit atively.