The evolution of interfaces for underwater gas jets is the main morphological manifestation of two-phase unstable interaction. The high-speed transient photographic recording and image post-processing methods are used to obtain the interfacial change in a submerged gaseous jet at different stages after its ejection from the Laval nozzle exit. The relationship between the pressure pulsation in the wake flow field and the interfacial change is further analyzed by combining the experimental results with computational results. A theoretical model is employed to address the competition dominant mechanism of interface instability. The results show that the jet interface of a supersonic gas jet gradually changes from one containing wave structures to a transition structure, and finally forms a steady-state conical jet. The fluctuation of the jet interface results in the pulsation of the back-pressure. The dominant mechanism of the interface changes with the development and distribution of the jet, from Kelvin-Helmholtz (K-H) instability beyond the nozzle exit changing to Rayleigh-Taylor (R-T) instability in the downstream.

The docking mechanism is a key component for on-orbit refueling technology. In this paper, the design and analysis of a novel floating docking mechanism for on-orbit berthing-based refueling is presented. Compared with traditional berthing and docking, the berthing here is high in success rate and low in impact, which is accomplished by stretching out a docking subassembly instead of pulling back the client spacecraft. However, the berthing also has two problems: initial deviations between two spacecraft and an additional force generated by a hard alloy refueling pipe, which both seriously affect the docking operation. Thus, the docking mechanism is designed to have alignment abilities and decrease the additional force as much as possible. Based on the principles above, we introduced spring pins and a helical refueling pipe to design a light, compact, and simple docking mechanism. To further reduce the additional force, we proposed an elliptical-helical pipe and analyzed its mechanical properties. Finally, simulations and experiments were conducted to validate the proposed mechanism. The results show that the proposed mechanism with an elliptical-helical pipe has a high tolerance for linear and angular misalignment and superior dynamic performance during docking.

The size distribution of condensed products during the combustion of aluminized propellants and flow characteristics of the gas-solid two-phase flow in solid rocket motor were studied in this paper. Firstly, based on the laser scattering technology, an online detection system for condensed products in plume was established, and the size detection of condensed products in the plume of solid rocket motor is carried out. Secondly, a numerical model of two-phase flow in solid rocket motor is established by combining the real size distribution of products in the plume with discrete phase model through the Rosin-Rammler distribution function. Besides, numerical simulation research is carried out under the same experimental conditions, focusing on the influence of condensed products with real size on the characteristics of solid rocket motor. The results show that the innovation measurement system can be used to obtain the size distribution characteristic of condensed products in the plume. At the particle size of stable stage, the mean size, D v 50 , is 104 μm, which is the smallest among all stages. It is also suggested that condensed products at the end stage have the most impact on the flow behavior in solid rocket motor, in that the shock structure, Mach number, and temperature distribution in the near field of plume are significantly changed.