Microjet Generator for Highly Viscous Fluids
Microjet Generator for Highly Viscous Fluids
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DOI：
10.1103/physrevapplied.9.014035
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发表时间：
2018-01
影响因子：
4.6
通讯作者：
H. Onuki;Yuto Oi;Y. Tagawa
中科院分区：
文献类型：
--
作者：
H. Onuki;Yuto Oi;Y. Tagawa
本文描述了一种简单而新颖的系统，用于产生高粘性微射流。射流是在部分浸没在液体中的可润湿细管内产生的。管内的气液界面最初是凹形的，但比管外的气液界面深得多。施加在液体容器底部的脉冲力导致管内液体显着加速，随后由于凹面界面而发生流聚焦。射流生成过程可分为发生在不同时间尺度的两部分，即冲击时间（冲击持续时间$\le O(10^{-4})$ s）和聚焦时间（聚焦持续时间$\gg O(10^{-4})$ s）。在冲击时间内，液体由于冲击而突然加速。在聚焦时间内，由于流动聚焦而出现微射流。为了解释冲击时间内管内的突然加速，我们开发了一个基于压力脉冲方法的物理模型。数值模拟证实了所提出的模型，表明液体由于冲击力而加速的基本机制已被阐明。值得注意的是，在冲击时间内，粘性效应可以忽略不计。相反，在聚焦时间中，粘度在微射流的产生中起着重要作用。我们通过实验和数值研究了不同粘度的微射流的速度。我们发现较高的粘度会导致喷射速度降低，这可以用雷诺数（惯性力与粘性力之间的比率）来描述。这种新颖的设备可能是下一代技术的起点，例如高粘度喷墨打印机，包括生物打印机和用于微创医疗的无针注射设备。
This paper describes a simple yet novel system for generating a highly viscous microjet. The jet is produced inside a wettable thin tube partially submerged in a liquid. The gas-liquid interface inside the tube, which is initially concave, is kept much deeper than that outside the tube. An impulsive force applied at the bottom of a liquid container leads to significant acceleration of the liquid inside the tube followed by flow-focusing due to the concave interface. The jet generation process can be divided into two parts that occur in different time scales, i.e. the Impact time (impact duration $\le O(10^{-4})$ s) and Focusing time (focusing duration $\gg O(10^{-4})$ s). In Impact time, the liquid accelerates suddenly due to the impact. In Focusing time, the microjet emerges due to flow-focusing. In order to explain the sudden acceleration inside the tube in Impact time, we develop a physical model based on a pressure impulse approach. Numerical simulations confirm the proposed model, indicating that the basic mechanism of the acceleration of the liquid due to the impulsive force is elucidated. Remarkably, the viscous effect is negligible in Impact time. In contrast, in Focusing time, the viscosity plays an important role in the microjet generation. We experimentally and numerically investigate the velocity of microjets with various viscosities. We find that higher viscosities lead to reduction of the jet velocity, which can be described by using Reynolds number (the ratio between the inertia force and the viscous force). This novel device may be a starting point for next-generation technologies, such as high-viscosity inkjet printers including bioprinters and needle-free injection devices for minimally invasive medical treatments.