Experiment Research And LBM Based Simulation Of Droplet Impinging On Liquid Film

The impact of droplets upon liquid film on solid surface is one of the mostcommon phenomena in nature and in industry. The impact will result in complexflows such as deposition, splash, and rebound. The research on the flowsinduced by droplets impinging on liquid film has much importance to scienceand industry appliance, and has much value in practical application.Lattice Boltzmann Method (LBM) is a mesoscopic method to simulate fluidflows, which has clear physical background, good parallelism, and is easy tohandle boundary conditions. Because LBM is a Kinetic model, it has manyadvantages compared with conventional computational fluid dynamic methodswhen handling two-phase flows. Much progress has been made in simulation oftwo-phase flows of vapor and liquid by LBM in recent years. And it is becomingan effective method for simulation of two-phase flows.In this thesis, the flows in a pistol caused by droplets impacting on liquidfilm were simulated numerically, and experiments were carried out to analyzethe phenomenon of the flows caused by two droplets impinging on liquid film.The main works carried out are as follows.1) The LBM pseudopotential model for two-phase flow was employed tosimulate the flows caused by droplet impinging on the liquid film in a closedpistol. In this model, a pseudopotential function was explored by introducing theequation of state of non-ideal gas, which was then used to mimic the interactionsbetween fluid particles. So this model is capable to simulate the two phase flowof vapor and liquid. To validate the capability of this model to simulatetwo-phase flow, the phase separation and two droplets’ integration weresimulated. On this basis, the flow process of droplet impinging onto liquid filmin a chamber was simulated, and the influence of temperature on the process was analyzed.2) The double distribution function LBM two-phase model was employed tosimulate the flows induced by droplets impinging on the liquid film on solidsurface in a closed pistol. In this model, the interaction between fluid particleswas written as two forms, ie, the potential form and the stress form. Coupledwith these two forms interaction in accordance to the two distribution functionsfαand gαwere introduced, which were employed to simulate the density fieldand the momentum and pressure, respectively. The simulation of two droplets’integration was then carried out to validate this model. The two-phase flowcaused by droplets impinging on the liquid film in a closed chamber wassimulated by this model, and the affection of the density ratio of liquid andvapor on the flow was analyzed.3) High speed photographic instrument was used to record the splashprocess caused by two droplets separated by certain distance impinging theliquid film in a certain time interval, and the causes of the interactionphenomenon was analyzed.