Model and experiments of a drop impinging on an immersed wall

We present a model describing the rebound of a drop impinging on a rigid pl ane wall immersed in water. This model is based on the resolution of the dr op equation of motion in an unbounded fluid in which an additional pressure force is introduced accounting for the wall effect on the drop motion. Thi s force is computed from a film drainage simulation model during the approa ch of the deformable particle to the wall. Results of the model have been c ompared with experimental trajectories of drops impinging vertically at ter minal rise velocity against a horizontal wall immersed in water at rest. Th ese trajectories have been obtained with the help of an image processing te chnique. A wide range of experimental conditions has been studied (drop dia meter, interfacial tension, drop viscosity, and density). In most of the ca ses, the model predicts the experimental trajectories within a very good ac curacy (height of bouncing, deformation, number of rebounds) even in the ca se of a significant deformation. The numerical results show that the reboun d of a deformable inclusion against a wall in water is essentially governed by the balance between the added mass force and the film pressure force ex erted on the drop during the impact. The model has also been successfully t ested in the case of an impinging bubble at high particle Reynolds number, based on experimental data taken from Tsao and Koch [Phys. Fluids 9, 44 (19 97)]. (C) 2001 American Institute of Physics.