Investigation of geyser appearance and intensity of pipelines with a horizontal section in cryogenic rockets

To investigate geyser behavior in cryogenic pipelines containing horizontal sections—an engineering-relevant yet insufficiently studied configuration—a numerical model based on volume of fluid method is established and implemented in ANSYS FLUENT. The model is validated through comparison with experimental data from representative cryogenic fluid transfer systems. The fluctuation characteristics of thermophysical parameters and phase distribution are deeply analyzed. The influence pattern and mechanism of geometry parameters such as horizontal pipe diameter and length is revealed through a comprehensive comparison study. The conclusions can be made as follows. It is found that a horizontal condensation stage occurs in pipelines with horizontal sections which is a distinct difference from pipelines with only vertical sections. Moreover, a fluctuation development stage is observed prior to the establishment of stable geyser oscillations. The maximum duration of the fluctuation development is approximately 1.9 times of the geyser period. It is revealed that the horizontal section diameter determines the heat accumulation rate within the pipeline. A larger diameter results in a slower heat accumulation rate, leading to a longer fluctuation development time and geyser period. In contrast, the horizontal section length has little effect on the heat accumulation rate, as well as on the fluctuation development time and geyser period. Furthermore, it is found that greater gas-liquid two-phase flow resistance in the horizontal section reduces the number of bubbles entering the vertical section, leading to a lower geyser eruption intensity. Conversely, during the refilling stage, a larger bubble volume in the horizontal section enhances the buffering effect of the gas, thereby reducing the geyser refilling intensity.