Computational Study of Miniature Tube for Biomedical Application

Abstract

Needle-free injection devices are novel inventions to provide medications to patients without puncturing their skin with a needle. The present work focuses on the computational study of fluid flow characteristics inside the shock tube designed for liquid-type drug delivery and also evaluates these computational and analytical results with experimental observations. To observe primary and reflected shock pressure and shock Mach number for achieving the controlled microjet velocity to accelerate the drugs. ANSYS fluent has been utilized to solve the governing equations of energy, continuity, and momentum where density-based implicit solver is used to perform the transient analysis of the shock tube. Two combinations of gases (nitrogen-air and helium-air as a driver and driven section gas) have been considered for the CFD analysis. Four pressures ranging from 25-50 bar in the driver section and 1 bar in the driven area are considered as an initial condition to perform the simulations. The obtained results showed that the pressure and temperature ratios and Mach numbers are more significant for the helium-air model than for the nitrogen-air model at different operating pressures. These results are validated using analytical calculations, which also agree well with experimental results. Further, the microjet velocity has been calculated. The maximum value of microjet velocity for the nitrogen-air model is 62 m/s, whereas for the helium-air model is 106 m/s. The microjet velocity is more significant for the helium-air combination; hence the penetration depth on the target surface will be more effective on helium than nitrogen.