LIQUID SLOSHING IN A CYLINDRICAL QUARTER TANK

Abstract

With the increasing size of space vehicles and their larger diameter, both of which lower the natural frequencies of the propellants, the effects of propellant sloshing upon the stability of the vehicle are becoming more critical, especially since at launch usually a very large amount of the total mass is in the form of liquid propellant. With increasing diameter, the oscillating propellant masses and the corresponding forces increase. Furthermore, the nat- ural frequencies of the propellant become smaller and shift closer to the control frequency of the space vehicle. A relatively simple means of avoiding strong dynamic coupling of the propellant motion and the control system is represented by compartmentation of propellant containers with longitudinal walls. This results in smaller sloshing masses and larger natural frequencies. Free and forced liquid oscillations in form of translatory, pitching, and roll excitation have been determined for a cylindrical container of circular quarter cross sec- tion. The fluid was assumed to be irrotational, inviscid, and incompressible. The velocity potential of the liquid is obtained from the solution of Laplace's equation with linearized boundary conditions. Forces and moments of the liquid are obtained by integration of the pressure distribution along the container walls. The results of the theoretical studies com- pared with available experimental values are in good agreement.