Abstract

Many engineering devices have dynamic components and hence, their computational models are no longer fixed in space and time. In these cases, dynamic mesh method is often applied to analyze their motion or unsteady fluid dynamics around/inside them. This study deals with the engineering application of CFD particularly using dynamic mesh methods to simulate firstly the compressible transient flow in a needle-less liquid jet injector for biomedical application and secondly, the performance of a diaphragm-less shock tube design for investigation of high-speed compressible gas dynamics. The CFD software OpenFOAM® is used as the main research tool to carry out this study.
For the first application, the dynamic behavior of the liquid jet is approximated using multi-phase compressible immiscible fluids LES solver together with the Volume-of-Fluid (VOF) method for the interface capturing. The liquid retained in the injector chamber is impacted by the moving grid boundary to mimic the injector piston driven by the driver air pressure; and the high speed liquid jet is emitted to atmosphere region though a nozzle. Numerical results are validated and discussed by comparing with experimental measurements. Performance plots as a function of various injector parameters are constructed and explained.
The second application concerns with the diaphragm-less shock tube design which consists of an outer tube contained with high pressure and an inner one with low pressure.
A particular design of diaphragm-less shock tube utilizes a rapid opening sleeve to mimic the rupture of a diaphragm which is traditionally used to separate the two pressure region. Applying CFD with dynamic mesh to the sleeve motion contributes to the analysis of the process of shock wave generation in this device and the shock tube parameters such as opening time of the sleeve for reliable performance.
It is proven in this work that the numerical CFD models with dynamic mesh can accurately predict the performance of both engineering devices and provide a useful tool
to analyze which parameters most significantly impact the performances.