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The impact of droplets on metallic wire meshes is seen in many applications: mesh screens are used to separate liquid from wet steam; polymer meshes are used to capture water droplets from coastal mists in arid areas; sprinklers are used to quench fires in electrical enclosures that have windows covered with wire mesh. In all these cases it is important to know the mass flux and droplet sizes that either penetrate through the mesh or are captured by it. An experimental study was carried out to observe the impact of a full cone water spray onto horizontal stainless steel meshes that were stretched over a ring to maintain uniform tension. Three different meshes were used for the experiments, all having the same wire diameter (200 µm) while varying pore size (200, 400 and 800 µm). A high-resolution camera with a narrow depth of field was used to photograph droplets both above and below the plane of the wire mesh. Image analysis software was used to measure droplet size distributions from photographs. High speed video was taken of droplets impacting the mesh and penetrating through it. The mean droplet size was found to be in the range of 20-30 µm, much smaller than the mesh pore dimensions. However, droplets landing on the 200 µm pore mesh were seen to coalesce with each other and form a liquid film suggested they adhered to the wires and blocked the pore apertures. In the case of the mesh with 400 µm pores water dripping from the wires was observed so that the droplet size below the mesh was significantly larger than that of the impacting spray. Most droplets impacting the 800 µm mesh penetrated through the pores and no liquid layer was formed. A theoretical explanation is offered based on the impact statistics and the capillary filling of the pores.
