Microstreaming of a Pneumatically Controlled Bubble under Hydrostatic Pressure and Crossflow

Three-dimensional (3D) microstreaming bubbles can generate local turbulence and perturb bulk fluid flow, offering great potential for mitigating membrane fouling. However, the microstreaming generated by trapped atmospheric gas bubbles often diminishes under hydraulic pressure and crossflow due to gas compressibility, limiting their application in membrane processes. In this work, we explore the microstreaming effects of a pneumatically controlled bubble whose position, shape, and internal pressure can be adjusted within a fluid medium under varying hydraulic pressure and crossflow. We demonstrate that the pneumatic microstreaming bubble (PMB) can generate effective streaming in bulk fluid with hydraulic pressures up to 20 psi and crossflow velocities up to 19.3 mm/s, which are well within the operating range of membrane separation processes. The study outlines the working conditions and identifies key challenges for future integration of PMBs into practical membrane separation processes.