Akiomi Ushida

Huge reduction in pressure drop of water, glycerol/water mixture, and aqueous solution of polyethylene oxide in high speed flows through micro-orifices

Microfluid mechanics is one of the most exciting research areas in modern fluid mechanics and fluid engineering because of its many potential industrial and biological applications. In the present study, pressure drops (PDs) were measured for water, a 50/50 glycerol/water mixture, and a 0.1% aqueous solution of polyethylene oxide (PEO) 8000 flowing at high velocities through various sizes of micro-orifice. It was found that the measured PD of water and the glycerol/water mixture agrees with the prediction of the Navier–Stokes equation for orifices 100 and 400 μm in diameter, but it is lower for orifices less than 50 μm in diameter. In particular, the measured maximum PD was almost two orders of magnitude lower than the prediction for the 10 and 5 μm diameter orifices. The glycerol/water mixture, possessing a viscosity ten times higher than water, provided nearly the same PDs as water when the reduction was generated. The solution of PEO produced a lower PD than water and the glycerol/water mixture except ...

A simple expression for pressure drops of water and other low molecular liquids in the flow through micro-orifices

Flows are generally divided into two types: shear flows and shear-free elongational (extensional) flows. Both are necessary for a thorough understanding of the flow properties of a fluid. Shear flows are easy to achieve in practice, for example, through Poiseuille or Couette flows. Shear-free elongational flows are experimentally hard to achieve, resulting in an incomplete understanding of the flow properties of fluids in micro-devices. Nevertheless, flows through micro-orifices are useful for probing the properties of elongational flows at high elongational rates; although these flows exhibit shear and elongation, the elongation is dominant and the shear is negligible in the central region of the flows. We previously reported an anomalous reduction in pressure drops in the flows of water, a 50/50 mixture of glycerol and water, and silicone oils through micro-orifices. In the present paper, we rearrange the data presented in the previous paper and reveal a simple relationship where the pressure drop is pr...

Effect of Microbubble Mixtures on the Washing Rate of Surfactant Solutions in a Swirling Flow and an Alternating Flow

Abstract Wastewater from laundry cleaning contributes to water pollution, and the amount of detergent used needs to be reduced. In the present study, water, four types of surfactants, and their microbubble mixtures were used, and washing rates were measured in swirling flows and alternating flows. The microbubble/water mixtures (average particle diameter: 25 μm; mixed with air at 1.5 vol % in water) achieved washing rates higher than those of water alone. Furthermore, microbubbles mixed with an aqueous surfactant solution had a washing rate that depended on the ionization of the surfactant: the mixtures with microbubbles and non-ionic and anionic surfactants had a washing rate that was higher than that of aqueous non-ionic and anionic surfactant solutions without microbubbles. The surface tensions of microbubble/water mixtures and mixtures of microbubbles with non-ionic and anionic surfactants were lower than those without microbubbles. These results provide evidence of an enhanced washing effect for microbubble mixtures in laundry cleaning.

Is the water flow more or less than that predicted by the Navier-Stokes equation in micro-orifices?

Micro-fluid mechanics is an important field in modern fluid mechanics. However, flows through microscale short tubes (micro-orifices) are not yet fully understood. Thus far, experiments on the flow through micro-orifices have been conducted by two methods: the pressure-given method (PGM), in which the pressure is given and the rate of flow is measured, and the flow-given method (FGM), in which the flow rate is given and the pressure is measured. According to conventional fluid mechanics, these two methods should give the same result; however, studies have found lower fluidity (lower flow rate) in PGM and higher fluidity (lower pressure drop) in FGM than that predicted by the Navier-Stokes equation, suggesting that the difference is caused by the method used. To clarify the cause of this difference, we examined the flow of ultra-pure water (UPW) with elapsed time by PGM. UPW was passed through Ni or Ti micro-orifices with 20-μm diameter at applied pressures of 50-1000 Pa. The difference in the shape and ma...

Anomalous Decrease in Flow Rates of Micro-Orifice Flows of Water With Increasing the Elapsed Time After Inception of the Flow

Flow rates under some pressure differentials were measured for the flow of water through micro-orifices. It was found that the flow rate decreases as the time has elapsed after inception of the flow under a constant pressure differential and that the decrease in flow rates is larger for city water than for pure water, and the gold orifice provides a less decrease with time in flow rates than the nickel orifice, although the flow rate at the incipient stage of the experimental run is lower in the gold orifice than in the nickel orifice.© 2011 ASME

Organic compounds generated after the flow of water through micro-orifices: Were they synthesized?

Micro-fluid mechanics is an important area of research in modern fluid mechanics because of its many potential industrial and biological applications. However, the field is not fully understood yet. In previous work, when passing ultrapure water (UPW) in which air was dissolved (UPW*) through micro-orifices, we found that the flow velocity decreased and stopped over time, and membranes were frequently formed in the orifice when the flow stopped. The membrane came from the dissolved air in UPW*, and membrane formation was closely related to electric charges generated in orifices by the flow. In the present paper, we clarified the components of the membrane and suggested a mechanism for membrane formation. We examined the effect of contaminants on the membrane formation and confirmed our previous results. We identified the chemical components of the membrane and those present in the UPW* itself by using an electron probe microanalyzer and found that the proportion of each element differed between the membrane and UPW*. Raman and infrared (IR) spectroscopy showed that the membrane consisted of organic substances such as carotenoids, amides, esters, and sugars. We irradiated UPW* with ultraviolet light to cut organic chains that may be left in UPW* as contaminants. We found a similar membrane and organic compounds as in nonirradiated UPW*. Furthermore, although the UPW that was kept from contact with air after it was supplied from the UPW maker (UPW0) and bubbled with Ar gas (UPW0 bubbled with Ar) formed no membrane, the UPW0 bubbled with CO2 formed thin membranes, and Raman and IR analysis showed that this membrane contained carboxylic acid salts, carotenoids, or a mixture of both. We found that electric grounding of the orifice reduces the probability of membrane formation and that the jets issuing from an aperture bear negative charges, and we assumed that the micro-orifices possess positive charges generated by flows. Consequently, we suggest that organic compounds are synthesized from nonorganic matter in air or CO2 dissolved in water by the action of hydroxyl radicals generated by flows through micro-orifices.

354. Rheological Modification of Hydrodynamic Gene Delivery

The aim of this study is to clarify whether a rheological modification of hydrodynamic gene delivery (HGD) has a potential to sustain gene delivery efficiency with a limited injection volume.A saline-based DNA solution corresponding to 5% of body weight (NS) instead of 9%, which is used in a canonical HGD, was injected from the mouse tail vein with pCMV-Luc at 10 mg/ml in 5 sec. The activities of 6 kinds of solutes were evaluated to enhance gene delivery efficiency. Four solutes were contrast media (CM1-4) at 60 mg/ml of iodine concentration, which had various kinds of ionicity and osmolality. The others were mannitol (MAN) and glycerin (GLY), which were solubilized as the same concentration as that of a major component in CM1. Liver samples were collected 24 hours after the injections, and luciferase assay and immunohistochemistry (IHC) were conducted.The median values of luciferase activities after the delivery with CM1-4, MAN, GLY, and NS, and HGD were 3.2×109, 9.2×108, 3.5×109, 2.5×108, 1.4×109, 7.3×107, 1.7×106, and 1.6×1010RLU/mg of protein, respectively. In IHC, the distributions of luciferase-positive cells after the injections with the solutes were similar to that of HGD. The luciferase activity of CM1 was significantly higher than that of NS (n=5, 5, p<0.01, Mann-Whitney U test). The levels of luciferase activities were not significantly different among CM1-4 (n=5, 3, 3, 3, p=0.16, Kruskal-Wallis test). The luciferase activities between CM1 and MAN were not significantly different from each other (n=5, 3, p=0.57, Mann-Whitney U test). These results suggested that the ionicity, osmolality, and iodine were not a primary factor of gene delivery efficiency in HGD. Therefore, we focused on another property.Elasticity is one of rheological properties of liquids to return to their original shape after removing stress. When fluids pass though a micro-orifice, the passed liquids attract a flow though the orifice. In general, the attracting force gets higher as the temperature becomes lower.The luciferase activity of GLY, which had the lower elasticity than CM1, was not significantly higher than that of NS (n=3, 5, p=0.14, Mann-Whitney U test). Furthermore, median values of luciferase activities of CM1 at 10, 20, 30, and 37°C were 5.0×109, 1.3×109, 9.7×108, and 1.2×108, respectively (p<0.05, Kruskal-Wallis test), while the elasticity of CM1 got higher as the temperature was lower. Based on these results, we speculated that the solution elasticity was a promising candidate to sustain gene delivery efficiency with a limited injection volume in HGD.The next step is to explore a substance providing higher elasticity to a DNA solution, and to evaluate its safety.

Drag Reduction for Nanobubble Mixture Flows Through Micro-Apertures

Drag reduction effect for microbubble mixtures flows has been investigated and reported. However, few studies have focused on nanobubble mixtures, which have sub-micron meter size fine bubbles. In the present study, nanobubble mixtures for water and glycerol solution were passed through several sizes of micro-apertures, and the resultant pressure drops, as compared with water and glycerol solution alone, were evaluated. For small apertures, the experimentally measured pressure drop was less than that for water and glycerol alone. This phenomenon is considered in terms of interface behavior and attributed to the electric interaction between an electric double layer and fine bubbles. The results of the present study suggest that the addition of nanobubbles to a liquid results in excellent drag reduction.Copyright

Flow Properties for Several Kinds of Liquid Flows Through Micro-Orifices

In this paper, the flow properties of several types of liquid passing through various sizes of micro-orifices were investigated. 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.© 2011 ASME

Anomalous Reduction in Pressure Drops of the Water Flow through Micro‐Orifices in High Velocity Ranges

Micro‐fluid mechanics and its application is one of the most attracting subjects in recent fluid mechanics and fluid engineering. We measured the pressure drop in water flowing through micro‐orifices in high velocities approaching two hundreds meters per second at the maximum. It was found that the measured pressure drop agrees with the prediction of Navier‐Stokes equation for the orifice of 100 μm diameter, but it is lower than the prediction for the orifices less than 50 μm diameter, especially almost two orders of magnitude lower for 10 μm and 5 μm diameters. This huge reduction was confirmed to have no relation to the orifice shape whether the corner of the orifice hole is round or sharp. Also, deformation of orifice foils by pressurization was not a factor of this phenomenon.