Kyriazis Nikolaos, Koukouvinis Phoevos, Gavaises Manolis
Department of Mechanical Engineering and Aeronautics, School of Mathematics, Computer Science and Engineering, City University of London, Northampton Square EC1V 0HB, UK.
Proc Math Phys Eng Sci. 2019 Feb;475(2222):20180548. doi: 10.1098/rspa.2018.0548. Epub 2019 Feb 20.
The formation of a liquid jet into air induced by the growth of a laser-generated bubble inside a needle-free device is numerically investigated by employing the compressible Navier-Stokes equations. The three co-existing phases (liquid, vapour and air) are assumed to be in thermal equilibrium. A transport equation for the gas mass fraction is solved in order to simulate the non-condensable gas. The homogeneous equilibrium model is used in order to account for the phase change process between liquid and vapour. Thermodynamic closure for all three phases is achieved by a barotropic Equation of State. Two-dimensional axisymmetric simulations are performed for a needle-free device for which experimental data are available and used for the validation of the developed model. The influence of the initial bubble pressure and the meniscus geometry on the jet velocity is examined by two different sets of studies. Based on the latter, a new meniscus design similar to shaped-charge jets is proposed, which offers a more focused and higher velocity jet compared to the conventional shape of the hemispherical gas-liquid interface. Preliminary calculations show that the developed jet can penetrate the skin and thus, such configurations can contribute towards a new needle-free design.
通过采用可压缩的纳维-斯托克斯方程,对无针装置内部由激光产生的气泡生长所诱导的液体射流形成进入空气的过程进行了数值研究。假设三个共存相(液体、蒸汽和空气)处于热平衡状态。为了模拟不可凝气体,求解了气体质量分数的输运方程。采用均相平衡模型来考虑液体和蒸汽之间的相变过程。通过正压状态方程实现了所有三相的热力学封闭。对一个有实验数据的无针装置进行了二维轴对称模拟,并将这些数据用于验证所开发的模型。通过两组不同的研究考察了初始气泡压力和弯月面几何形状对射流速度的影响。基于后者,提出了一种类似于聚能装药射流的新型弯月面设计,与传统的半球形气液界面形状相比,它能提供更聚焦、速度更高的射流。初步计算表明,所形成的射流能够穿透皮肤,因此,这种结构有助于新型无针设计。