Abstract
Spreading behavior of ink droplets in a rectangular hollow surrounded by banks were studied by using a numerical simulation. Droplets that collide with the bottom of the hollow collapse vertically within several μs. Then they extend in the radial direction at a low speed. After the outer part of the droplet reaches the nearest hydrophobic bank, it runs up on the bank and retreats, so the droplet extends in the direction of its long side, keeping the width of its short side. When the contact angle on the banked slope is smaller than the slope angle, the progressing side of the droplet becomes concave in the traveling direction.
