Sloshing of viscous fluids: Application to aerospace

TL;DR

This paper develops a theoretical model for viscous fluid sloshing in tanks, validated experimentally, and creates an algorithm to predict fluid behavior under excitation, with applications to aerospace rocket propellants.

Contribution

It introduces a new theoretical model for viscous fluid sloshing and an algorithm for predicting fluid behavior under excitation, applied to aerospace contexts.

Findings

Higher resonant frequencies lead to greater attenuation.

Adding viscous layers increases damping significantly.

The Matlab algorithm shows promising results but has convergence issues.

Abstract

This bachelor project presents a theoretical model describing the resonant frequencies in rectangular and cylindrical tanks. It presents an experimental validation in the rectangular case. The resonant frequencies are determined and then used to construct a theoretical model for the free damping of viscous fluids. The predictions of the model are qualitatively analysed. The higher the resonant frequency, the higher the attenuation associated with that mode. Adding a layer of a more viscous liquid, even a thin one, significantly increases the attenuation. In addition, the addition of a layer of polystyrene beads prevents excitation at low frequencies. However, experiments are still needed to find out exactly what physical phenomena explain this. In addition. Finally, an algorithm is designed and implemented in a Matlab code to determine the behaviour of the liquid when subjected to a horizontal sinusoidal excitation. The results of the algorithm are promising, but it still encounters convergence problems for extreme cases. The algorithm can be used to make theoretical predictions for rocket propellants. The application of this research to the Bella Lui rocket of the EPFL rocket team is discussed.