BUBBLE DYNAMICS IN TEMPERATURE SENSITIVE NON-NEWTONIAN GEL PROPELLANT

Gel propellants, which are classified as non-Newtonian fluids exhibiting shear-thinning effects, have rheological properties that are influenced by temperature. During the manufacturing and filling process of gel propellants, it is quite common for gas to be inadvertently mixed in, which can have a detrimental impact on engine performance. In order to comprehensively investigate and analyze the intricate dynamics of bubble motions within gel propellants, this paper adopts the volume of fluid (VOF) method to simulate the rising process of a single bubbled driven by buoyancy in static gel propellants, in which the extended Carreau-Yasuda model coupled with temperature is used for the viscosity of the gel propellants, and the surface tension of the gel is calculated using the continuum surface force (CSF) model. By changing the parameters such as temperature, rheological index, characteristic time, and surface tension in the gel, we observed the variation of viscosity and shear rate in the non-Newtonian fluid. Subsequently, we studied their effects on the aspect ratio, centroid position, and velocity of the bubbles. The study also examined the influence of two parameters, namely rheological index and characteristic time, on the motion of bubbles at various temperatures. The results show that the high viscosity of gel propellants will hinder the movement of the bubbles and limit its deformation, so the deformation of the bubble is not significant; the increase in temperature will reduce the viscosity of gel propellants, which will significantly affect the trajectory and shape of the bubble increasing the rising speed of the bubble and intensifying the deformation; the rheological index and characteristic time will affect the velocity and aspect ratio of the bubble by changing the liquid properties; moreover, it is found that the alteration of surface tension will exert a greater impact on the deformation occurring at the bottom part of the bubble.