Direct numerical simulation of bag-breakup - mechanism of sea spray generation in strong winds

Abstract

For the direct numerical simulation of the bag-breakup phenomenon, the Gerris flow solver was used. As an initial configuration for numerical simulation a drop of liquid was placed in the air flow. A drop of water with a diameter of 1 cm (the characteristic size of the perturbation from which the bag arises) placed in the air stream at a speed of 20 m/s corresponds best to the experimental situation, such a system is characterized by the Weber number We = 54. Modeling the dynamics of two media with very different densities, such as water and air, require a lot of computational time, so we used liquids that differ in density by a factor of 10, but to keep the same Weber number, we changed the other parameters of the problem. The calculation was carried out with keeping the same Reynolds number and also with the Reynolds number reduced and increased by a factor of 10. In our simulation just as in an experiment under the action of an air stream a drop is blown into a micro-sail that bursts to form a micro-spray. As the Reynolds number decreases (with increasing of viscosity of both media), the process of destruction of the drop after the formation of a micro-sail from it changes.