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Athree − dimensional direc 亡numerica 】sin ］ulation (DNS)with Level − Set me 亡 hod is applied to the impingement proces ＄ of a t ingle droplet with diameter of 1 ． 2-2 ． 2mm on the air − water free surface ， and the characteristics of vortices induced below the free surface are investigated l)y comparing with the experiments 、 The restllts show tha 亡 the present DNS call capture the generation and transporta − tion process of the vortices ． The predict 巳d vortex intensity corresponds with the experimental best − fit curve pr 叩 osed for a larger droplet with diameter of 2 ． 2-5． 6mm ． In addition ， the compurisons nf velocity vectors and scular concentration fields between the vertical and oblique impingements show that the mornentum and mass transfcr mechanism are strongly affccted by the angle of droplet ' s irnpingernent ． Key 理 brd8 ： Direct Numerical Simし亘latiQn ， Liquid Drop 星 et ， Interfacial Phenomena ， Gas − Liquid Two − Phase Flow ， Mixing