Effects of Air Pressure and Wettability on Drop Impact on Dry Surfaces Taehun Lee, Department of Mechanical Engineering, City University of New York, City College, New York, NY 10031 This proposal aims at modeling the effects of air pressure on drop impact on dry surfaces with difference wetting characteristics and investigating drop dynamics after impact under different conditions. A recent experiment has discovered that the surrounding air pressure is an important parameter for creating a splash on a smooth dry substrate so that the splash can be completely suppressed in a low pressure environment. This discovery has important applications in the design of internal combustion engines in that the size distribution of fuel drops will be affected or can be controlled by changing the pressure inside. We focused on the effects of wettability on drop impact and developed proper boundary conditions for the lattice Boltzmann equation method. We proposed three types of polynomial boundary conditions (linear, quadratic, and cubic) based on the wall energy approach for the accurate prediction of the contact angle and density distribution close to a solid surface (Liu and Lee, in press). When the fluids have large property contrast and the impact of the gas phase on wetting is small (e.g., water-air system), the higher-order boundary condition may be a natural choice. LBM simulations (Lee and Liu in review): sequence of images for a water drop impact on the dry surfaces whose equilibrium contact angle is θ = 107o; Re = 687, We = 103, and Oh = 0.0148.