イベントカメラによるひも状ミセル水溶液中を沈降する球まわりのせん断波伝播の可視化

抄録

This study aimed to elucidate the mechanism of sudden acceleration of a sphere settling in a wormlike micellar solution. To this end, high-time-resolution birefringence observations were performed using an event camera. In the experiment, a stainless steel sphere with a diameter of 6.35 mm was permitted to settle in a stationary aqueous solution of CTAB/NaSal (30 mM, counterion molar ratio 4). The visualization of shear waves was achieved using the crossed polarizers method, which was then observed with an event camera. The results revealed significant differences between two successive rapid accelerations within a short time interval. Immediately following the initial rapid acceleration, birefringence was observed to be temporarily enhanced directly behind the sphere. Strong shear waves were generated from behind the sphere during the subsequent rapid acceleration. These observations are partially consistent with the previously reported rubber-band-cutting model and allow for the estimation of the cutting position. Using an event camera enabled the detailed observation of high-speed phenomena that were previously difficult to capture.