Damping and Ejection of Sloshing Liquid Drops from Elastic Substrates

Liquid slosh is a potential source of disturbance of the motion of a moving structure. In this thesis, we probe the damping technique of sessile drop by absorbing a portion of the kinetic energy. The sloshing dynamics are typically represented by a mechanical model of a spring mass damper. However, damping by drop sloshing is dependent on viscosity, surface tension, drop size and drop location. We explore highly-coupled fluid-solid mechanics using singular liquid drop with varying viscosity and surface tension resting on a millimetric cantilever. Cantilevers are displaced 0.6 mm and their free end is allowed to vibrate freely. Cantilever vibration causes drops to deform, or slosh, which dissipates kinetic energy via viscous dissipation within the drop. A solid weight with the same mass as experimental drops is used to compare the damping imposed by liquids, thereby accounting for other damping sources. Neither the most viscous nor least viscous drops studied imposed the greatest damping on cantilever motion. Instead, drops of intermediate viscosity strike the most effective balance of sloshing and internal dissipative capacity. The removal of pinned drops from small, delicate surfaces such as sensors and flight surfaces on micro-flyers can be challenging due to remote location and small scale and they require large deflection. Robustness is enhanced when such surfaces, of comparable scale to deposited drops, can remove deposition without external influence. Drop ejection for drops larger than the capillary length, can be a complicated, multi-stage event in which fluid removal occurs through multiple mechanisms in sequence. In this combined experimental and theoretical work, we propose drop release mechanism from elastic materials and characterization of drop sloshing damping. In our primary work, we observe three principal modes of drop release that can be singly witnessed under the appropriate set of cantilevers and drop conditions. We categorize these three release modes as sliding, normal-to-cantilever ejection, and pinch-off. We found that, the selection of system variables such as cantilever length L (a proxy for stiffness), drop location, drop size and wettability allows for the solicitation of a particular ejection mode

最適化問題に対するブレインストーム最適化アルゴリズムの改善

富山大学・富理工博甲第170号・于洋・2020/3/24富山大学202