[O-08] Kitchen Earth Science: its potential for producing diverse goals by hands-on experiments

[O08-02] Nonlinear oscillators in nonequilibrium conditions

★Invited Papers

*Hiroyuki Kitahata¹ (1.Graduate School of Science, Chiba University)

Keywords:nonlinear oscillator, synchronization, rhythm

Rhythmic behaviors can emerge in chemical, biological, and hydrodynamic systems under nonequilibrium conditions. Biological clocks, oscillatory chemical reactions, and hydrodynamic convective flows are well-known examples. Such rhythmic behaviors are stable against external perturbations and have characteristic amplitude and period. They are called nonlinear oscillations since nonlinear terms should be included in the model for such behaviors. We have studied several experimental systems in which nonlinear oscillations emerge. In the presentation, several experimental systems are introduced. First, we introduce the so-called density oscillator. A small chamber filled with higher-density liquid is put in a large chamber filled with lower-density liquid and a small pore is prepared at the bottom of the small chamber. The upward flow of the lower-density liquid and the downward flow of the higher-density flow alternate through the pore. We changed the density difference between the two liquids and found that the bifurcation occurs between the non-oscillatory state and the oscillatory state [1]. The numerical simulation considering the hydrodynamic equation reproduced the bifurcation [2]. Using the same model, we discussed the synchronization modes when several oscillators are coupled [3]. Next, we introduce the oscillatory breakup of the layer generated at the liquid surface. We prepared a camphor methanol solution. At the solution surface, a camphor layer was generated through the evaporation of the methanol. The temperature increase due to the decrease in evaporation makes the camphor layer dissolve. Once the camphor layer is dissolved and a liquid surface appears, the evaporation of methanol decreases temperature and the camphor layer is generated again. Through the repetition of these processes, we could observe the oscillation of the camphor layer generation [4,5].
[1] H. Ito, T. Itasaka, N. Takeda, and H. Kitahata, EPL, 129, 18001 (2020).
[2] N. Takeda, N. Kurata, H. Ito, and H. Kitahata, Phys. Rev. E, 101, 042216 (2020).
[3] N. Takeda, H. Ito, and H. Kitahata, Phys. Rev. E, 107, 034201 (2023).
[4] T. Sasaki, N. J. Suematsu, T. Sakurai, and H. Kitahata, J. Phys. Chem. B, 119, 9970 (2015).
[5] Y. Onishi, H. Kitahata, and N. J. Suematsu, Phys. Rev. E 109, 044801 (2024).