A numerical study of surface tension effects on the break-up behavior of transcritical fuel droplets

The role of surface tension is typically neglected in transcritical flow simulations. However, recent experiments and theoretical studies have shown that surface tension persists at high pressures. It is still, however, unproven if the presence of the surface tension force significantly changes the flow and mixing behavior in transcritical flow problems. A fully compressible diffuse-interface method is developed to simulate the breakup of a single transcritical droplet impacted by a shockwave to replicate the high-speed convective flows at engine-relevant conditions. Using this model, we investigate the significance of surface tension on droplet break-up by implementing the surface tension coefficients between the fuel (n-dodecane) and the surrounding fluid (nitrogen) obtained from molecular dynamics simulations. The breakup mode of the transcritical droplets is identified for a wide range of velocity, temperature, and pressure conditions.