Added Masses of generic shape bodies interacting with external walls

Abstract

The aim of this paper is to propose an efficient method to evaluate the Added Masses of generic shape bodies in infinite fluid or in the proximity of external walls. The Added Masses (AM) are the result of the inertial reaction of the fluid in response to an accelerated movement of a body immersed in it. The AM effects are more evident when the body density is similar to that of the surrounding fluid, as in the case of airships. In the take-off or landing phases, the proximity to the ground causes an increase in the Added Masses that must be correctly estimated to properly size the airship controls. In our method, the calculation of the Added Masses matrix is carried out by the Boundary Element Method (BEM). To verify the accuracy of the results, the study cases are based on simple shapes, whose Added Masses are well known. The analyses in infinite fluid and in the presence of a flat wall are carried out. Numerical results are compared to the theoretical values found in literature. The calculated Added Masses are intrinsically dependent on the mesh definition and the relative error, referred to the theoretical values, depends on the surface and volume discretization. In the case of interaction between geometries with complex shapes, the influence on the Added Masses is very difficult to predict without a numerical approach. The method proposed gives a good compromise in terms of quality of results and computational cost.