2流体モデルによる粗氷形成の数値シミュレーション  [in Japanese] Numerical Simulation of Hard-Rime Accretion Based on 2-Fluid Model  [in Japanese]

Employing unsteady 2-fluid equation of multiphase flows as a mathematical model of flows including super-cooled droplets, we apply Eulerian approach to ice-accretion problem. A coupled system of equations for airstream and suspended water droplets is solved numerically with FDM and local impingement efficiency (mass flux of droplets on a body surface) is estimated. The temporal change of the shape of accreted ice is obtained from the local impingement efficiency and the renewal of grid distribution is performed. We also describe some difficulties on Eulerian approach in icing problems. These are mathematical property of the basic equations, the deterioration of representing the body shape due to the lack of grid point and stiffness due to large difference of characteristic time scales. In particular, the second difficulty is overcome by the method for grid interpolation. Hard-rime accretion on a NACA0015 air foil is simulated by means of the present procedure. In particular, the effect of two different definitions of local impingement efficiency and two different growth directions to the accreted ice is investigated. Comparison with an experimental observation shows that the simulated ice shape of local impingement efficiency with the uniform velocity direction and normal direction growth reproduces successfully the experimental results.