Atomisation of a pulsed liquid jet by Volume of Fluid method

Simulation of a pulsating dense cylindrical liquid oil jet injected into a stagnant air phase is performed at Reynolds number Re=5800, Weber number We=5555 and density ratio r=28 using the Volume of Fluid method and octree adaptive mesh refinement, using the Basilisk code. The grid refinement above 900 cells per initial jet diameter is achieved. This is to our knowledge the most detailed simulation of this type of flow. Simulations provide direct evidence of many underlying mechanisms including characteristic sheet perforation due to droplet impact and sheet rupture due to stretching and thinning. The numerical curvature provides a diagnostic of the presence of weak spots. After holes form from weak spots, characteristic ligament networks are seen. The probability distribution function (PDF) of droplet sizes is obtained. It converges slowly with the minimum grid size ∆ and has a bimodal character. The position of the two peaks is a shifting showing towards small scales as ∆ is decreased, indicating the dependence of the mechanisms involved on the grid size, with sheet perforation the likely culprit. At large scales, however, the PDF is seen to be converging.