No abstract

Physiologically, blood ejected from the left ventricle in systole exhibited spiral flow characteristics. This spiral flow has been proven to have several advantages such as lateral reduction of directed forces and thrombus formation, while it also appears to be clinically beneficial in suppressing neurological complications. In order to deliver spiral flow characteristics during cardiopulmonary bypass operation, several modifications have been made on an aortic cannula either at the internal or at the outflow tip; these modifications have proven to yield better hemodynamic performances compared to standard cannula. However, there is no modification done at the inlet part of the aortic cannula for inducing spiral flow so far. This study was carried out by attaching a spiral inducer at the inlet of an aortic cannula. Then, the hemodynamic performances of the new cannula were compared with the standard straight tip end-hole cannula. This is achieved by modeling the cannula and attaching the cannula at a patient-specific aorta model. Numerical approach was utilized to evaluate the hemodynamic performance, and a water jet impact experiment was used to demonstrate the jet force generated by the cannula. The new spiral flow aortic cannula has shown some improvements by reducing approximately 21% of impinging velocity near to the aortic wall, and more than 58% reduction on total force generated as compared to standard cannula.

No abstract

In order to extract maximum amount of energy possible from the automotive reciprocating engine exhaust gas, the turbocharger usually installed closely downstream the exhaust valve thus exposing it to highly pulsating flow conditions. This condition induces highly complex flow field within the turbocharger stage and significantly impact its performance characteristics which is not fully understood. The main objective of this paper is to provide understanding of unsteady flow feature using a Computational Fluid Dynamics (CFD) approach validated with experimental data. Despite focusing on unsteady feature of the flow, this research also emphasizes the importance of accurately modelled geometry in the early section of the paper. A steady state validation against experimental data is performed prior to unsteady calculations. The effect of different phase shifting methods is described and the relationship of instantaneous efficiency with incidence angle is established. In the final section of this paper, the turbocharger stage is sectioned where its instantaneous performance is evaluated individually in each section. The unsteady simulation is performed at fixed 30 000 RPM with 20Hz pulsing flow.