Refined equivalent modeling of sloshing dynamics in the multi-ballonet system of stratospheric airship

Multiple ballonets are arranged within the airship, each confined to an individual section by diaphragms. The gas-air interface within the ballonet sections induces sloshing, which subsequently influences the motion of the airship. This paper presents an equivalent mechanical model for simulating gas sloshing in multiple ballonet sections to better understand this influence. Building on previous work, which employed a spring-mass-dashpot system to model sloshing in a tank and utilized the strip method to represent a horizontal cylinder by accumulating tank slices, this paper further introduces a frequency normalization process to enhance the cylinder model, thereby enabling the simplification of an individual section of the airship in which the ballonet is located. Based on these individual ballonet sections, a final multi-ballonet sloshing model is established, providing a quantitative understanding of the sloshing forces and moments under variations in airship layouts, ballonet numbers, and air filling levels. The sloshing behavior of the airship’s multi-ballonet system is similar to that of a multi-compartment horizontal cylinder, showing limited sensitivity to the air filling level and an optimal number of ballonets, with 5 to 6 being ideal for airships like the YEZ-2A. This model facilitates the development of a motion-sloshing model, enabling airship designers to efficiently account for multi-ballonet gas sloshing effects during the initial design and control stages, contributing to more accurate airship motion modeling.