Effect of thickness to diameter ratio on micro-orifice single-phase liquid flow at low Reynolds number

Micro-orifice discharge with single-phase water flow was experimentally investigated with six multi-micro-orifice test pieces with orifice diameter of 200 µm and thickness to diameter ratio between 4.25 and 27.0. During the experiments the Reynolds number varied between 5 and 4500: a range that corresponds to creeping flow and laminar to turbulent transitional flow. The emergence of turbulence, as indirectly deduced from the change in slope of the pressure drop versus mass flow rate profiles, was found to be gradual and smooth. Using the newly generated data presented here, the validity of an existing micro-orifice discharge prediction method for creeping flow conditions was extended to microfluidics applications with thick micro-orifices.