[O-07] Kitchen Earth Science: its potential for producing diverse goals by hands-on experiments

[O07-P06] Airjet into Dilatant Fluid

★Invited Papers

*Tasuku Saiki¹, Ken Yamamoto², Makoto Katura², Hiroaki Katsuragi² (1.Department of Physics, School of Science, Osaka University, 2.Department of Earth and Space, Graduate School of Science of Osaka University)

Keywords:Dilatant Fluid, Airjet

Dilatant fluid elastically responds to the rapid deformation-like impact. This enables us to even run on the pool of dilatant fluid. The physical origin of this peculiar feature of dilatant fluid has not been fully understood yet. The solid impact on the surface of dilatant fluid presumably induces a solid plug that grows to reach the bottom of the container. Then, this solid plug causes the elastic response. While this explanation can explain some experimental observations, a sufficient understanding of the rheological properties of dilatant fluid has not been achieved. To reveal the fundamental rheological properties of the dilatant fluid, other types of experiments might also be useful. Thus, in this study, we performed a novel experiment in which an air jet impinges onto the surface of a dilatant fluid layer. We prepared a dilatant fluid layer (mixture of potato starch and water whose mass ratio is 1.5:1) of size 200 * 230* 50 mm. Then, the air jet of pressure 0.3 MPa ejected from a nozzle of diameter 3 mm is vertically impacted onto the surface of the dilatant fluid. The resultant deformation of the impacted dilatant fluid layer was captured by a camera. By varying the thickness of the dilatant fluid layer and the distance from the nozzle tip to the surface of the dilatant fluid, resultant behaviors were observed. Based on the measured results, we found a novel phenomenon. When the air jet nozzle is close and the thickness of the dilatant fluid layer is sufficiently thick, tunnel-like structures can be formed. In addition, partial levitation behaviors can also be observed under a certain condition. While the physical understanding of these observed phenomena has not been established yet, systematic experiments allow us to discuss what controls these phenomena. In the presentation, examples of the observed movies and possible ideas to explain the observed phenomena will be provided.