title: Effect of bubble flow velocity on drag-force and shear stress working on submerged hollow fibre membrane.
abstract: This study is aimed at elucidating the mechanism by which rising air bubbles induce shear stress on hollow fibre membrane surfaces. Shear stress on hollow fibre membrane surfaces (laterally-set and vertically-set) caused by aeration was measured directly using a two-direction load sensor. In the laterally-set hollow fibre module, time-averaged upward-direction shear stress on the membrane surface was compared to theoretical shear stress values considering the effect of water flow on membrane surface. Measured time-average shear stress values were almost 200 times larger than theoretical values implying strong interactions between bubbles and solid surface. In the vertically-set membrane module, velocity measurement of bubble flow using laser Doppler velocimeter revealed that drag force working on membrane surface was closely related to upward-direction water velocity. Also fluctuation of drag force and shear force on membrane surface was found to be related to velocity fluctuation (turbulence).
authors.affiliation: Department of Civil Engineering, Musashi Institute of Technology, Tamazutsumi 1-28-1, Setagaya-ku, Tokyo, 158-8557, Japan. hnagaoka@sc.musashi-tech.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Nagaoka
authors.forename: M
authors.initials: M
authors.lastname: Kurosaka
authors.forename: N
authors.initials: N
authors.lastname: Shibata
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
mesh_terms: D019149:Bioreactors; D008567:Membranes, Artificial; D011673:Pulsatile Flow; D013314:Stress, Mechanical; D013499:Surface Properties; D018508:Water Purification / Q000295:instrumentation* / Q000379:methods
chemical_list: D008567:Membranes, Artificial