This paper focuses on the impact of sloshing loads on a lightweight tank for a next generation agile launch vehicle during the ascend phase of the flight. For this analysis the partially filled oxidizer tank is considered. The launch vehicle is designed to provide active trajectory control during the propulsion phase and to assure structural integrity of the tank during disturbances like shear winds etc. Therefore, a full–scale tank has been produced of composite material in order to investigate the sloshing behavior inside the partially filled tank experimentally. As the tank is made of composite material there is no optical assessment because this material is opaque. In order to predict the natural frequencies and the maximum rebound forces, a methodology based on analytical and numerical simulation has been set up in order to predict the liquid dynamics for different tank fill levels. The influence of sloshing on the is analyzed using a linear mechanical spring–mass–system in combination with a real–time 3D particle–cluster method.
The behavior of liquids inside a spacecraft has always been subject to indeep analysis since the beginning of the space age. For liquid propulsion, the fuel provides a significant contribution to the overall mass, and therefore the knowledge of the mass properties of the fuel is extremely important for performance and safety considerations. (Bauer, 1963) was one of the pioneers in analyzing the effect of propellant sloshing on large launch vehicles, here the Saturn V rocket. At the same time, (Stephens, 1965) used a linear mathematical model for ideal fluids validated against experimental data. In the following years, (Bauer et. al.) further optimized the mathematical description of liquid sloshing using series expansion of the governing mechanical equations by Fourier transformation. (Dodge, 1965) extended this model and carried out a comprehensive study on the natural modes for different tank shapes. With rising computer power and more practical knowledge from previous launch campaigns, (Unruh et. al., 1986) published a digital data analysis methodology that combined the test data acquisition with physically based mathematical description of sloshing frequencies and loads. For the sloshing behavior in microgravity, (Vreeburg and Veldman, 2002) have worked on a CFD–based methodology using the Volume–of-Fluid (VoF) method to capture the free surface of liquids in spacecraft tanks without the influence of gravity. Their efforts have been demonstrated in practice during the SloshSat—FLEVO mission, a scientific satellite designed for the analysis of sloshing in microgravity. Sloshing in partially filled tanks is a complex physical process. It covers phenomena like wave propagation and liquid-structure interaction, see (Yamamoto et al., 1995). Applying continuum fluid mechanics for a simulation approach, Euler and Navier–Stokes solvers provide a time accurate simulation only if an appropriate free surface determination and propagation is implemented. In consequence, computation time and required memory resources increase with increasing code complexity and accuracy requirements Recent approaches consider statistical methods for the wall pressure determination see (Gervaise et al., 2009). Briefly, there is still a big amount of uncertainty concerning the physical background of liquid sloshing effects.