This chapter deals with capillary instability of straight free liquid jets moving in air. It begins with linear stability theory for small perturbations of Newtonian liquid jets and discusses the unstable modes, characteristic growth rates, temporal and spatial instabilities and their underlying physical mechanisms. The linear theory also provides an estimate of the main droplet size emerging from capillary breakup. Formation of satellite modes is treated in the framework of either asymptotic methods or direct numerical simulations. Then, such additional effects like thermocapillarity, or swirl are taken into account. In addition, quasi-one-dimensional approach for description of capillary breakup is introduced and illustrated in detail for Newtonian and rheologically complex liquid jets (pseudoplastic, dilatant, and viscoelastic polymeric liquids).

Handbook of Atomization and Sprays

Droplet impact on superhydrophobic surfaces: A review of recent developments

Computational fluid dynamics modeling of compartment fires

The Leidenfrost effect is undesirable in cooling applications as the vapor layer on which the liquid levitates acts as a heat transfer barrier. Here, we report on increasing the Leidenfrost temperature by surface textures that can promote droplet wetting at high superheat via capillary wicking. Counterintuitively, we find that sparser rather than denser textures increase the Leidenfrost temperature. Our experimental results are consistent with a physical model that balances capillary wetting pressures with dewetting pressures exerted by the escaping vapor. The physical mechanism suggests that hierarchical textures have a higher Leidenfrost temperature compared to single-length-scale textures, which is confirmed experimentally.

G. Grant

Papers

Fire suppression by water sprays