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Liquid unloading is a very common and important issue in horizontal gas wells, and the presence of curve sections increases the complexity of the phenomenon and its study. Liquid loading in a gas well will sharply reduce production, therefore, the liquid-unloading onset of different curved pipes is essential to gas production. In this work, liquid-unloading onset experiments were conducted in curved pipes with different curvatures. Then, the critical gas velocity VsgCR can be determined according to the measured pressure gradients, liquid holdup, and liquid film reversal. This work analyzes the factors which will lead to the liquid unloading and explores the trend of the pipe curvature’s influence on the liquid unloading under laboratory conditions. The experimental results show that the critical gas velocity rises with the increase of pipe curvature, the increase is mainly due to the centrifugal force. The present work also compares the predicted results of the OLGA model and Beggs–Brill model with experimental data. The comparison results indicate that both models fit relatively well to the experimental data at the low superficial gas velocity, and both models have poor performance at high superficial gas velocity. The OLGA model fits the experimental data better than the Beggs–Brill model at high superficial gas velocity. The error analysis shows that most of the predicted data is not in good agreement with experimental data. Some errors between experimental data and calculation results are out of the range of 50%.

In order to describe the near space communication channel efficiently and analyse the the reasons that cause quality deterioration of ground-to-air communication link, design the Channel modelling program of the near space and establish the near space channel model based on the DS signal system which considers rain attenuation and multipath fading. Complete the analysis of rainfall impact on signal fading and estimate related parameters under different elevation. Set up the statistical model of multipath fading. Complete the simulation of Ka-band geostationary near space channel performance under different elevation. Draw bit error rate performance simulation curve under different weather conditions. The result of MATLAB simulation shows that the model can reflect the fading characteristic of the near space communication channel. This program improves the signal fading and interference tolerance. The findings can provide a better simulation Platform for the follow-up job according to the correctness and practicability of established model and be of great significance in exploration and research of near space communication.