The flow properties of several types of liquid passing through various sizes of micro-orifices were investigated in this paper. The jet thrust and pressure drops were measured for two polyethylene glycol solutions and four surfactant solutions. Different flow properties were found for the various surfactant solutions depending on the charge of the solute. For an anionic surfactant, the results were similar to those for water, whereas in the case of a cationic surfactant, both the jet thrust and pressure decreased greatly in comparison with the other test liquids. Finally, a nonionic surfactant exhibited a steep rise in the pressure drop at a particular value of the Reynolds number. In explaining this behavior, the liquid-solid interface and alignment of the surfactant molecules are considered, and consequently, it is strongly suggested that the elastic stress on elongational flows is a contributing factor. In addition, the decreases in pressure and thrust for polyethylene glycols are attributed to viscoelastic properties, regardless of the molecular weight of PEG.

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Jet thrusts of several kinds of liquids issuing through small orifices were measured and compared with the predictions from numerical simulations of the Navier-Stokes equations. Reasonable agreements for so-called Newtonian fluids were obtained between the experimental and predicted thrusts for capillaries and orifices with openings of the order of 100 μm size, but the experimental thrusts were found to be below the predictions for orifices of the order of 10 μm. It was suggested that water and glycerol solutions have an elastic property for elongational flows passing through small orifices. As to surfactant aqueous solutions, cationic surfactant(BC) and non-ionic surfactant(AE (23)) provided thrusts lower than those of water, but anionic surfactant(LAS) showed almost the same thrusts as water. Also, lower thrusts were measured for dilute polymer aqueous solutions of PEO(18). A mean elastic stress for the tested liquids was evaluated by using the measured thrusts, and discussion was made on the idea that flows near the wall are affected by an interaction between anions on the surface of orifice and charged molecules of surfactants.

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