Multi-scale simulation of rainwater morphology evolution on a cylinder subjected to wind

• A multiscale model combining VOF with Lagrange particle methods is employed.
• The rainfall intensity effects are taken into account in the model.
• Four patterns are categorized during the entire evolution process.
• Circumferentially vibrating dynamic rivulet is observed.
• Rainwater morphology is characterized by the wind inflow velocity.

Numerical simulations of rainwater morphology evolution on a cylinder subjected to wind are investigated. Direct numerical simulations (DNS) and large eddy simulations (LES) are combined to simulate this complicated process based on a 2-D multiscale model. A Lagrange particle method is used to simulate rain droplets in the LES zone, far away from the cylinder surface. When droplets fall into the DNS zone, i.e., near the cylinder surface, the particles are converted into liquid droplets. The volume-of-fluid (VOF) method is then adopted to capture the morphology of the interface of the liquid–gas system. Rainwater morphology evolution along the circumference of cylinder can be categorized into four patterns over the analysis of the entire evolution process: collision–splashing, accumulation–slipping, formation–breaking, and dynamic equilibrium. The morphological characteristics of rainwater of each pattern are summarized. The circumferentially vibrating upper rivulet across the cylinder surface is observed. The resultant multiscale model is validated by comparison with the previous results from related studies.