Modeling Flow Recirculation Inside a Holding Chamber

Abstract

The present project analyses the streamlines patterns that influence the efficiency of the holding chambers (used in asthma treatment) and relate it with the geometric dimensions of the device. According to some unpublished observations, the utmost significant drug delivery faction for the treatment (the fine particle fraction below 6.0 μm in diameter) gets trapped in the recirculation areas of the holding chamber. Reducing the size of these recirculation areas will improve the device efficiency. This paper makes use of computational fluid dynamic techniques, as a method to avoid the need for the construction of traditional prototypes, thus reducing the cost of the research process. It was possible to obtain the size of the recirculation area in an automatic way and to relate such pattern with the geometric details of the holding chamber. An alternative design is compared with the Volumatic®, which is the widest used device. Results support the possibility in reducing the recirculation area inside the device by changing the wall geometry. By analyzing the influence of the length and diameter ratio of the expansion section of the holding chamber, it was concluded that longer lengths and lower diameter ratios yield a reduction of the recirculation area. The results bring a better understanding of the influence of geometry in the recirculation area and therefore in the holding chamber efficiency.