10:45 〜 12:15
[PPS07-P08] ダスト凝集に『繊維状物質』が与える影響
～部屋の埃から微惑星形成まで～
キーワード：微惑星形成、ソフトマター、ダスト、衝突、反発係数
The current observations and numerical simulations suggest that highly porous dust aggregates would grow into kilometer-size planetesimal. According to previous works, it has also become clear that interstellar gas-mediated dust aggregates can develop chain-like structure under microgravity conditions. [1,2,3]
It has been considered that collisional growth of highly porous, middle-size dust aggregates is not easy due to the bouncing and fragmentation. However, entanglement of chain-like materials might be able to overcome this problem. Therefore, we performed the low-speed collision experiments of dust aggregates consisting of chain-like materials to clarify the mechanical properties of such dust aggregates.
As a first step, we conducted free-fall collision experiments using a dust aggregate impacting onto a flat hard floor. To form dust aggregates, we used silk threads of various lengths. In order to record the motion of dropping dust aggregate, we built an experimental system by which a dust aggregate can be dropped in a vacuum chamber. Using a high-speed camera, we succeeded in filming single dust-aggregate impact at about 0.2 atmospheric pressure condition.
As a result, we found that the dust aggregate exhibited elastic behavior with energy dissipation. By image analysis of the acquired high-speed (300 fps) movie, it was confirmed that there is no correlation between the restitution coefficient of the dust aggregate and the length of threads constructing dust aggregates. The average value of restitution coefficient obtained in this experiment is 0.26 ± 0.02. However, in this analysis, the approximation method used to estimate the restitution coefficient is probably too simple. Thus, more accurate approximation and modeling of the collisional motion is required.
As a future problem, we would like to perform collision experiments with dust aggregates composed of various size threads. The velocity dependence of the restitution coefficient is also an important issue. We have also filmed the collisional coalescence of two dust aggregates in the vacuum chamber. The data of single dust-aggregate collision and two dust-aggregate collision should be combined to properly understand the general features of dust aggregate collisions. We believe that this research will provide clues to clarify the collision phenomena that occurs in actual space.
[1] D. Paszun and C. Dominik. ”The influence of grain rotation on the structure of dust aggregates”. Icarus, 182, 274 (2006).
[2] J.Blum et al., ”Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System”. JoVE, 2014 Jun 5
[3] S.Iwano et al., "Effect of "fibrous materials" on dust agglomeration". The Physical Society of Japan 2022 Spring Meeting, 15aB10-7, (2022)
It has been considered that collisional growth of highly porous, middle-size dust aggregates is not easy due to the bouncing and fragmentation. However, entanglement of chain-like materials might be able to overcome this problem. Therefore, we performed the low-speed collision experiments of dust aggregates consisting of chain-like materials to clarify the mechanical properties of such dust aggregates.
As a first step, we conducted free-fall collision experiments using a dust aggregate impacting onto a flat hard floor. To form dust aggregates, we used silk threads of various lengths. In order to record the motion of dropping dust aggregate, we built an experimental system by which a dust aggregate can be dropped in a vacuum chamber. Using a high-speed camera, we succeeded in filming single dust-aggregate impact at about 0.2 atmospheric pressure condition.
As a result, we found that the dust aggregate exhibited elastic behavior with energy dissipation. By image analysis of the acquired high-speed (300 fps) movie, it was confirmed that there is no correlation between the restitution coefficient of the dust aggregate and the length of threads constructing dust aggregates. The average value of restitution coefficient obtained in this experiment is 0.26 ± 0.02. However, in this analysis, the approximation method used to estimate the restitution coefficient is probably too simple. Thus, more accurate approximation and modeling of the collisional motion is required.
As a future problem, we would like to perform collision experiments with dust aggregates composed of various size threads. The velocity dependence of the restitution coefficient is also an important issue. We have also filmed the collisional coalescence of two dust aggregates in the vacuum chamber. The data of single dust-aggregate collision and two dust-aggregate collision should be combined to properly understand the general features of dust aggregate collisions. We believe that this research will provide clues to clarify the collision phenomena that occurs in actual space.
[1] D. Paszun and C. Dominik. ”The influence of grain rotation on the structure of dust aggregates”. Icarus, 182, 274 (2006).
[2] J.Blum et al., ”Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System”. JoVE, 2014 Jun 5
[3] S.Iwano et al., "Effect of "fibrous materials" on dust agglomeration". The Physical Society of Japan 2022 Spring Meeting, 15aB10-7, (2022)