Effect of Static Contact Angle in Simulations of Coaxial Gas-assisted Atomization*

Atomization plays a crucial role in many engineering systems such as combustion engines and agricultural sprays. Air-blast atomization is a specific spray strategy which relies on a high-speed gas to shear and break up a low-speed liquid, transferring its kinetic energy into liquid surface energy. In studies of air-blast atomization in a coaxial geometry, X-ray radiographs have shown non-trivial contact line dynamics and simulations have shown a strong dependence of the contact line boundary condition on the spray. In this study, we perform simulations of air-blast atomization at fixed atomization conditions but vary the static contact angle. Simulations are performed using a conservative finite volume flow solver with phase tracking handled using an un-split, geometric volume-of-fluid method. The static contact angle is modeled by adding a sub-grid scale interfacial tension force at the triple contact line. A single-phase nozzle simulation is run concurrently and coupled with the atomization simulation to yield realistic gas velocity inflow conditions. Our simulations are validated against experiments by comparing jet-width statistics and liquid mass distribution in the near-field. Finally, we discuss the effect of static contact angle on streamwise interfacial wave characteristics.