Morphological classification of disintegration behavior of viscoelastic simulant gel propellant in coaxial streams

In this study, the spray structure of simulant gel propellant was analyzed morphologically and qualitatively to understand the basic characteristics of the gelled jet disintegration process in a shear coaxial environment. Categorization of breakup process was conducted based on the water jet breakup theory with generalized Reynolds number of the Herschel–Bulkley model and aerodynamic Weber number. Similar breakup types and disintegration process comparable to Newtonian fluids were depicted. However, the disintegration development was relatively slow compared to Newtonian cases, and the spray structures were quite different especially in fiber-type breakup due to its inherent viscosity change and viscoelastic properties. In the case of gel propellant, a strong Reynolds number dependency was observed under a certain critical value of the generalized Reynolds number, whereas beyond this value, breakup regime can be categorized with only the Weber number as in Newtonian cases. The border of Reynolds number dependency was shown at approximately $$\text{Re}_{\text{gen}} = 200$$ for all simulant gel contents cases considered in this study. The Weber number ranges for the three breakup modes (Rayleigh type, membrane type and fiber type) were found, and a new breakup mode showing a more intricate gel disintegration than the Newtonian one is proposed. .