Water drop impacts on a single-layer of mesh screen membrane: Effect of water hammer pressure and advancing contact angles

Abstract

Mesh screen membrane is a functional material for gas-water or oil-water separation. If a water drop impacts on the membrane at a sufficiently high velocity, a critical condition at which daughter droplets are generated and fall down below the membrane occurs, under which the separator is failure. The objective of this paper is to determine the critical condition. Six mesh screen membranes are used. The mesh wire diameter and mesh pore are on the same-scale (10–100μm), involving apparent cross sectional area decrease of mesh pores in the membrane depth direction. Thus, drop impacting on the membrane yields significant liquid compression in ∼μs timescale to cause additional water hammer pressure. The analysis shows that the liquid compression is related to the number of mesh pores within drop project area (N). The water hammer pressure relative to dynamic pressure is found to be raised with N. The drop impacting process is governed by the dynamic pressure together with the additional water hammer pressure competed with the maximum capillary pressure at the throat location of the mesh pore. The modified Weber number −Wew/cos(θA) was correlated with N in a single curve to predict the critical condition for droplet breakthrough, where Wew is characterized by the mesh pore width and cos(θA) reflects the advancing contact angle effect. This paper is useful for membrane type gas-water or oil-water separator design.