On the relations between two-phase flows under reduced gravity and earth experiment

Experiments under varying gravitational intensity are costly and bear high difficulties. The present paper relates to the possibility of extracting some understanding on two-phase flow characteristics in space from 'equivalent systems' operating under earth gravity. It is shown that zero or reduced gravity is not only a matter of prescribing the gravitation intensity. Based on physical concepts, a distinction is made herein between 'microgravity' conditions, where stratification is completely avoided, and finitely reduced gravity systems, which may still demonstrate stratified configuration. The sodenoted 'microgravity' systems are defined by Eotwos number smaller than 1 and can be realized under normal earth conditions. As such, the various flow patterns relevant in space and the transitional boundaries are discussed in terms of 'equivalent systems' under normal gravity. Comparison with limited space data is satisfactory.