Off centered impact of water droplets on a thin horizontal wire

The current work focuses on the initial stage of filtering droplets, and explores the influential factors of drops impacting on a thin horizontal dry wire. We investigate the effect of the impact velocity, wire thickness, initial drop size and liquid surface tension along with the impact eccentricity, i.e. the distance between the trajectory of the drop and the axis of the wire, on the amount of liquid trapped on a wire. It was found that for high impact velocities (1.35, 1.41 m/s), the amount of liquid that remains on the wire is minimal and is fairly constant. For low and medium velocities (0.46-1.25 m/s), the amount of liquid that remains on the wire increases at a critical eccentricity value (from 0.2 to 2 mg), and from there it decreases. As the velocity increases, the maximum amount of liquid captured on the wire decreases while the corresponding critical eccentricity increases. This behavior was first observed and explained by Lorenceau et al. [5]. For a centered impact, the droplet is divided into two independent fragments, where each volume is bigger than the critical cature volume [5]. These fragments do not remain on the wire, and are detached under the effect of gravity and inertia. Only a small fraction of liquid remains on the wire in this case, following coating theorems. As the eccentricity increases, less equal the two lobes become, till the volume of one of them get smaller than the critical volume, consequently, it remains on the wire under the effects of the capillarity and friction that keep it from falling. An additional increment of the eccentricity above the critical value results a decrease of the captured fragment, till it extinct at e∼R. These findings led to a development of a criterion that characterizes the amount of liquid that can be captured by a wire. The criterion is based on a force balance and includes 4 non-dimensional (Re, We, Fr and the wire-drop radii ratio). The critical eccentricity and the max amount of captured liquid have been calculated and compared with experimental observations. A good agreement was found. Therefore, our equation provides a reliable criterion to determine the amount of liquid captured by a wire.