The problem of fluid injection into a viscoplastic fluid (i.e., a gelled material) attracts attention due to its wide applications (e.g., drug delivery systems, 3D printing technologies, mixing systems, oil and gas industries, etc.). In this work, motivated by the jet cleaning process in the plug and abandonment of oil and gas wells, we experimentally study the jet flow dynamics wherein a Newtonian fluid is horizontally injected into a viscoplastic ambient fluid. The jet and ambient fluids are miscible, while the domain is divided into two main zones by a perforated wall, motivated by the application. This complex flow is comprehensively analyzed using a combination of non-intrusive experimental techniques, including time-resolved tomographic particle image velocimetry (TR-Tomo PIV), high-speed imaging, and planar laser induced fluorescence (PLIF). We succeed to identify four distinct jet flow patterns: the mixing regime, the mushroom regime, the fingering regime, and the fracturing regime, and we compare their behaviour in terms of morphologies, velocity fields, etc. Finally, we show that the transition between the regimes is controlled by a dimensionless number found based on the balance of the yield stress and the characteristic inertial stress.
This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License. Any reuse must credit the author(s) and provide a link back to this page.