| 講演要旨： |
High speed video images of drops colliding with flat, dry solid surfaces reveal that, for large drop impact velocities, the drops flatten and form a ring structure. On sufficiently hydrophobic surfaces, the drop eventually recedes toward a more compact shape and a filament of liquid is ejected from the surface. On more hydrophilic surfaces, the film may continue to spread until the static contact angle is reached. In the case of relatively hydrophobic surfaces, one can identify four distinct regimes of the interaction between the drop and the surface. During the initial kinematic phase, the dimensionless wetting radius follows a universal form if the drop Weber and Reynolds numbers are sufficiently large. In the second phase, the drop becomes highly flattened and a ring is formed. The time evolution of the dimensionless wetting radius depends on the Weber and Reynolds numbers during this phase. In the third phase, the drop recedes, and the wettability of the surface becomes important. In the final phase, the drop reaches equilibrium. This talk will focus on the first two phases. The results to be discussed were obtained using a version of the lattice Boltzmann method developed by Inamuro, Ogata, Tajima, and Konishi. The results will be compared with published experimental results, and the prospects for accurately simulating all four of the above phases will be assessed. Prospects for performing simulations for drop impacts on more hydrophilic surfaces, and geometrically complex surfaces will also be discussed. |
