Numerical analysis for propellant management in liquid rocket tank

Abstract

In order to track three-dimensional behavior of liquid surface in storage tanks on orbit, a numerical scheme based on the Level Set Method was developed. For the verification of the numerical methods, experimental data were acquired through the observation on the unsteady deformations of liquid surface in cylindrical containers under low-gravity conditions in a drop tower. Main concern was placed on the relation between the value of dynamic contact angle and the behavior of the contact line on the solid wall. Based on the results, the boundary condition for surface tension was discussed and the model of wetting phenomena was adequately introduced into the computation. Compared with the experimental data, the corresponding numerical results obtained with the wetting model showed a quite good agreement. The flow fields at the draining process in the LOx tank for the LE-5B engine under low-gravity conditions were also investigated with the developed code. It was found that the buoyancy induced by a slight acceleration was efficient to prevent the dip growth, and that the serviceable propellant in the launch-vehicle tank could thereby be increased in a realistic situation. Introduction With the progress of human activities in space, the occasion to handle liquids under low gravity conditions is now growing. In weightless flights, the absence or diminution of gravity force makes it extremely difficult to position and control two-phase fluid in a desirable manner'. For the establishment of the technology for fluid * Graduate Student ** Associate Professor t Deputy Project Manager Copyright © 2001 The American Institute of Aeronautics and Astronautics Inc. All rights reserved. management in space, it is essential to accumulate technical knowledge to give appropriate assessment of designed fluid management systems for space application. However, in the atmosphere, there are not so many opportunities to realize the low-gravity state with airplanes or drop towers. The investigation methods with CFD (computational fluid dynamics) are therefore strongly desired. In the present paper, the algorithm of, what is called, CEP-LSM was developed to simulate threedimensional behavior of liquid surface driven by surface tension, wetting phenomena and gravity force. The free-surface flows under low gravity conditions were both experimentally and numerically investigated to verify the algorithm and to study the appropriate boundary conditions. Drop Tower Experiment In the present study, the unsteady deformations of liquid surface under low-gravity conditions were observed through a transparent vessel of cylindrical shape. The series of experiments aimed at acquiring the basic knowledge of free-surface flows driven by surface tension, and at obtaining the data suitable for the verification of the CFD code and the discussion on the boundary condition. Experimental Facilities The present experiments were conducted at the drop tower, shown in Fig.l, constructed in the University of Tokyo. As is shown in Fig.2, the drop box was composed of an inner box including the test vessel made of poly-acrylate resin, and an outer box of 920 mm wide, 610 mm deep, and 700 mm high in dimension. Liquid behaviors were observed through transparent wail of the test vessel with the CCD camera equipped on the observation section and recorded on a VCR. 1 American Institute of Aeronautics and Astronautics (c)2001 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.