Hydrodynamic analysis of the water landing phase of aircraft fuselages at constant speed and fixed attitude

Abstract

In this paper the hydrodynamics of fuselage models representing the main body of three different types of aircraft, moving in water at constant speed and fixed attitude is investigated using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) level-set flow solver χnavis. The objective of the CFD study is to give insight into the water landing phase of the aircraft emergency ditching. The pressure variations over the wetted surface and the features of the free surface are analysed in detail, showing a marked difference among the three shapes in terms of the configuration of the thin spray generated at the front. Such a difference is a consequence of the different transverse curvature of the fuselage bodies. Furthermore, it is observed that at the rear, where a change of longitudinal curvature occurs, a region of negative pressure (i.e. below the atmospheric value) develops. This generates a suction (downward) force of pure hydrodynamic origin. In order to better understand the role played by the longitudinal curvature change on the loads, a fourth fuselage shape truncated at the rear is also considered in the study. The forces acting on the fuselage models are considered as composed of three terms: the viscous, the hydrodynamic and the buoyancy contributions. For validation purposes the forces derived from the numerical simulations are compared with experimental data.