Hasegawa Tomiichi, Ushida Akiomi
Faculty of Engineering, Niigata University, 8050-2 Ikarashi, Nishi-ku, Niigata-shi, Niigata, 950-2181, Japan.
Institute of Science and Technology (Faculty of Engineering), Niigata University, 8050-2 Ikarashi, Nishi-ku, Niigata-shi, Niigata, 950-2181, Japan.
Sci Rep. 2024 Dec 28;14(1):30869. doi: 10.1038/s41598-024-81768-2.
Water flows through microscopic orifices have attracted much research interest recently because of their many potential industrial, biological, and medical applications, as well as their importance in the physics of fluids. In this study, by using circular nickel micro-orifices with diameters of 5-100 µm and applying pressures from 0.5 Pa to 0.6 MPa, the following anomalies were revealed. The velocity of water flowing through the 5-25 µm micro-orifices was 1.4-2.5 times higher than that through macro-orifices under low pressures and was close to the velocity of inviscid fluid under high pressures. The pressure divided by the dynamic pressure was frequently independent of the thickness of the orifice and close to that of the infinitely thin orifice under low pressures, whereas it was almost unity under high pressures. Notably, the flow rate often decreased gradually or steeply to negative values under applied pressures, whereupon either nickel or nickel and organic substances were found in and around the orifice. The velocity through the circular polyimide micro-orifice was substantially lower than that through macro-orifices, and a polyimide-like substance developed in the orifice. The effect of the organic substances found in the orifice on the flow properties was discussed.
由于其在许多潜在的工业、生物和医学应用中的重要性，以及在流体物理学中的重要地位，水流经微小孔口的现象最近引起了广泛的研究兴趣。在本研究中，通过使用直径为5 - 100微米的圆形镍微孔口，并施加0.5帕至0.6兆帕的压力，发现了以下异常现象。在低压下，水流经5 - 25微米微孔口的速度比流经大孔口的速度高1.4 - 2.5倍，在高压下接近无粘性流体的速度。压力除以动压在低压下通常与孔口厚度无关，接近无限薄孔口的情况，而在高压下几乎为1。值得注意的是，在施加压力下，流速常常逐渐或急剧下降至负值，随后在孔口及其周围发现镍或镍与有机物质。水流经圆形聚酰亚胺微孔口的速度明显低于流经大孔口的速度，并且在孔口中形成了类似聚酰亚胺的物质。讨论了孔口中发现的有机物质对流动特性的影响。
