The flow in the bronchial tube was experimentally investigated using a human bronchial tube model. Resin bronchus model that is made by 3D printer is provided for the experiment. a bent pipe is connected upstream of the bronchus model. Microbubbles were used as tracers to visualize the movement of particles. The areas to be photographed are the secondary flow in the curved pipe and around the first branch of the bronchial model. Velocity distribution is measured by PIV. Refractive index matching technique are applied to measure velocity in the bronchus model. In front of the first branch of the bronchial model, the velocity distribution of the inverse pressure gradient was observed. In the right and left bronchi, the position of the peak is more medially biased due to this effect.
