The analysis of violent sloshing is of great interest for European aeroplane manufacturers. It has been widely reported that aircraft fuel sloshing significantly damps wing vibrations, but the complexity of the fluid-structure phenomena still demands further research. The aim of this work is to define an experimental methodology to quantify the sloshing force acting on a vertical Single Degree Of Freedom (SDOF) tank when the accelerations are similar to the ones found in a real wing. In this work, two different methodologies are presented for the calculation of the sloshing force involved in the SDOF tests, finding a very good level of agreement between them. A Froude scaled SDOF experiment has been devised for sloshing study, confirming first that the fluid presence increases the damping of the system notably, and second that the slosh-induced damping force is composed of an inertial term and a dissipative term. The sloshing force study also shows that this force is shifted with respect to position measurements, and this phase-shift is a key element in fluid-induced energy dissipation. A global energy study connecting the sources of energy dissipation with the forces involved in the dynamics of the system is performed, obtaining a quantitative contribution of the fluid's role in the system. Finally, a numerical model has been tested using the experimentally obtained sloshing forces as an input exhibiting good agreement with the previously obtained experimental results.

A dynamical system involving the decaying test of a partially filled liquid tank is analyzed in the present paper. This analysis is relevant for the design of aircraft fuel tanks, where the wings' structural dynamics are influenced by the complexity and the violence of the internal flow generated when atmospheric turbulence or gust is encountered. The study of this kind of system is performed in order to understand the extra energy dissipation caused by the confined fluid, and the interacting force between the fluid and the tank resulting from the vertical sloshing. A complete non-dimensional analysis of the problem in terms of additional damping has been performed, and the dependency on the most relevant non-dimensional numbers has been monitored. A coupled numerical simulation where both the tank and the fluid are combined has been used to study the system, and their results are compared to previous experiments. A smoothed particle hydrodynamics model, extensively validated in the sloshing literature, is used to calculate the magnitude and frequency of the vertical force between the fluid and the tank. The extra dissipation of the tank's mechanical energy caused by the fluid action is quantified for a particular configuration with constant filling level and a wide range of non-dimensional numbers. The sensitivity of the extra damping to the variation of the non-dimensional numbers is evaluated, and the most relevant ones are compared to the equivalent experimental tests. Results show that the numerical tool developed is able to capture the different phenomena involved and can be used to determine the influence of the different phenomena happening in violent vertically excited flows.

The aim of this work is to provide a reduced-order model to describe the dissipative behavior of nonlinear vertical sloshing involving Rayleigh–Taylor instability by means of a feed forward neural network. A 1-degree-of-freedom system is taken into account as representative of fluid–structure interaction problem. Sloshing has been replaced by an equivalent mechanical model, namely a boxed-in bouncing ball with parameters suitably tuned with performed experiments. A large data set, consisting of a long simulation of the bouncing ball model with pseudo-periodic motion of the boundary condition spanning different values of oscillation amplitude and frequency, is used to train the neural network. The obtained neural network model has been included in a Simulink®  environment for closed-loop fluid–structure interaction simulations showing promising performances for perspective integration in complex structural system.

In Paper I of this series [Marrone, Colagrossi, Gonzalez,"A numerical study on the dissipation mechanisms in sloshing flows induced by violent and high frequency accelerations. Part I: Theoretical formulation and numerical investigation"], a theoretical formulation and the numerical model were developed in order to obtain a complete perspective of the energy balance of a violently accelerated flow confined inside a rectangular tank. The tank-fluid system was periodically excited with a predetermined law of motion and the force between the wall and the fluid and the global energy balance were computed. In this second part, the experimental validation of the previous formulation is presented. In order to make a comparison with a previous experimental campaign,

The wings of large civilian aircraft are designed to withstand a variety of loads whose causes range from atmospheric gusts to turbulence to landing impacts. Aircraft wings are essential structures that demand further research. One of the primary methods used for improving wing design is analysis of the damping effects that sloshing induces on the dynamics of flexible wing-like structures carrying liquids. This will be attained through the development of experimental set-ups that will help in building up numerical models that are used to reproduce the physics involved. Hence, the aim of this work is to analyze the effect of sloshing in reducing the design loads on aircraft structures using the numerical method Smoothed Particle Hydrodynamics (SPH) as the main numerical tool. One of the key considerations in this research is the demand for scaled experiments, making it a necessary step in assessing whether computational tools are able to approximate the registered measurements for different scales accurately. To this end, a numerical model of a vertically oscillating tank built as a fully coupled fluid-structure interaction problem is developed. The structure is modelled through a mass-spring-damper system, and for the inner fluid the δ-SPH methodology is used. In particular, two open questions are studied: the first one is to what extent gravity has an influence on the damping and energy dissipation phenomena when the initial acceleration of the tank is ten times the standard gravity value. The second seeks to confirm that the SPH equations correctly reproduce the scaling laws when the problem parameters are scaled according to the dimensional analysis.