Droplet Impact: A GPU Based Smoothed Particle Hydrodynamics (SPH) Approach

A parallel GPU compatible Lagrangian mesh free particle solver for multiphase fluid flow based on Smoothed Particle Hydrodynamics (SPH) scheme is developed and used to capture the interface evolution during droplet impact. To solve Navier-Stokes equations, the computational domain is discretized using fluid particles. Surface tension is modeled employing the multiphase scheme of Hu et al. In order to precisely simulate the wetting phenomena, a method based on the work of Šikalo et al. is used and compared to ensure accurate dynamic contact angle calculation. Using this method, accurate perditions were obtained for droplet contact angle during equilibrium and spreading. A simple analytical model is developed to predict maximum droplet spread diameter after impact. Solver predictions agreed well to analytical results. To improve stability and performance of the solver, a customized reduction algorithm is used on the shared memory of GPU. Speedup using a variety of different memory management algorithms on GPU-CPU is studied. The proposed algorithm is validated using the Rayleigh-Taylor instability test. Droplet impact simulations are compared side by side against a Volume of Fluid (VOF) solver to ensure accuracy and robustness. GPU speed ups of up to 120 times faster than a single processor CPU were obtained. Variations of droplet spread factor and recoil height during the impact are shown to be in good agreement with experimental results.