Abstract:

In order to investigate the spreading characteristics of droplets on the solid substrate from the mesoscopic scale, based on the lattice Boltzmann method(LBM), a two-dimensional dynamic wetting model of a single droplet was established in the D2Q9 physical model by discrete velocity and force. Using the above theoretical model, combined with the analytical solution, the accuracy of the model was verified. The dimensionless parameter Bond number was further introduced to characterize the influence of the relative size of gravity and surface tension on the wetting profile of droplets, and the influence of gas-liquid interface parameters and wall properties on contact angle and spreading coefficient was quantitatively analyzed. The results show that the final contact angle and spreading coefficient are determined by the inherent wetting properties and surface force of the solid substrate. The mutual conversion of potential energy and surface energy is the key to realize dynamic wetting of droplets. When the characteristic radius of droplet is not more than 25 at mesoscopic scale, the larger the droplet is, the smaller the final contact angle is, and the larger the spreading coefficient is. Once the critical value of the interval is exceeded, the final contact angle and spreading coefficient will tend to be fixed. The larger the solid base surface properties, the stronger the hydrophilicity, the smaller the final contact angle, and the easier the droplets spread. The greater the absolute value of the gas-liquid interface property, the smaller the surface tension, the greater the spreading coefficient, and the better the wetting effect.

Key words: droplet, mesoscale, wetting behavior, theoretical model, dynamic characteristics, contact angle, spreading coefficients, interfacial force