Oscillations of a drop in aerodynamic levitation

The aim of this work is to model the axisymmetric small-amplitude oscillati on modes of a liquid drop in aerodynamic levitation over a horizontal porou s wall. In this objective, the boundary element method (BEM) was chosen to solve numerically the unsteady Stokes equations in the frequency domain. Ar guments are presented to justify this choice. The use of this numerical met hod is quite original to describe coupled flows, such as those characterizi ng the levitation problem. A numerical tool, based on the BEM, was develope d to perform the normal-mode analysis for the axisymmetric oscillations. Th e set of unsteady Stokes equations and boundary conditions governing the be havior of the fluids in both internal and external domains led to a linear homogeneous system with pulsation as a parameter. The eigenvalues of this s ystem give the frequencies, while the associated eigenvectors provide the s hapes of the oscillation modes. A sensitivity analysis was performed to cho ose the optimal values of the numerical parameters. Furthermore, the study of the influence of the physical parameters revealed the consistency of the modelization. At last, a comparison with experimental results proved to be satisfactory. (C) 2001 Elsevier Science B.V. All rights reserved.