Nasal administration of the vaccine is in the spotlight and the medicine has been developed in recent years. The medication is carried out by spraying the medicine in the nasal cavity by collunarium container. The top nozzle part of a common collunarium container consists of three parts, nozzle tip having an exit, cylindrical nozzle, and stepped center rod which is inserted into the nozzle. We confirmed that the spray of collunarium container consists of two stages phenomena (initial jet and its disintegration, and steady spray stage) by visualization with high-speed video camera. Since we found that the initial jet impacted with larger droplet size than later sprayed droplet, we examined the initial jet and steady spray stage in experiments and numerical simulations to study the effect of material and dimension of the rod. The dimensions of the center rod affected the acceleration of the initial jet front and the spray angle in experiments. In numerical simulations including fluid-structure interaction (FSI), lower density rod moved at faster speed and excited higher flow velocity at the exit in the jet stage. Moreover we confirmed that the acceleration of the jet was initiated by the water hammer wave propagation inside the nozzle.

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