Japan Geoscience Union Meeting 2023

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS12] Geophysical fluid dynamics-Transfield approach to geoscience

Tue. May 23, 2023 1:45 PM - 3:00 PM 202 (International Conference Hall, Makuhari Messe)

convener:Keita Iga(Atmosphere and Ocean Research Institute, The University of Tokyo), Shigeo Yoshida(Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University), Takatoshi Yanagisawa(Research Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology), Hidenori AIKI(Nagoya University), Chairperson:Kensuke Nakajima(Department of Earth and Planetary Sciences,Flculty of Sciences,Kyushu University)

2:15 PM - 2:30 PM

[MIS12-03] Transient behavior of thermal turbulence in a rectangular vessel by imposing horizontal temperature gradient

*Kaito Yoda1, Yuji Tasaka1, Daisuke Noto2, Takatoshi Yanagisawa3, Yuichi Muraii (1.Faculty of Engineering, Hokkaido University, 2.University of Pennsylvania, 3.Research Institute for Marine Geodynamics, Japan Agency for Marine-Earth Science and Technology)

Keywords:Thermal turbulence, Horizontal conveciton , Baroclinic tourque, Flow structure

Various studies have conducted on Rayleigh-Bénard convection (RBC) caused by vertical temperature gradient as a basis for heat transfer and turbulence study. In addition, there exists horizontal convection (HC) driven by the baroclinic torque due to the imposition of a horizontal temperature gradient. The flow resulting from the superposition of RBC with HC is of fundamental interest and has potentially important applications in the environment.
We experimentally investigated transient behaviors from RBC to HC by imposing horizontal temperature gradients on forcing boundaries in addition to the vertical unstable temperature gradients. A rectangular vessel with an aspect ratio of two was used, and fixed vertical and horizontal temperature differences, 10°C, were imposed on the test fluid, water. Visualization of the temperature field and velocity distribution measurement were performed using thermosensitive liquid crystal particles as tracer particles and as temperature visualizer. We continuously observed flow fields for 120 min after imposing the horizontal temperature gradients to achieve quasi-steady states. Before the system being influenced by the horizontal forcing, thermal boundary layers were detached intermittently as thermal plumes leading to large-scale circulations (LSCs), which are variable in size and rotation direction. A LSC occupying the entire fluid layer was formed quickly, approximately 180 seconds after the horizontal forcing.
Instantaneous velocity vector fields were obtained by particle tacking velocimetry with nearest neighbor algorithm to quantify the transient behavior. Roughly 20,000 vectors were obtained on each snapshot of the sequential images. We thus calculated the probability density function of the velocity distributions and the angular momentum around the vessel center. Examining these time variations indicated that the LSCs in the thermal turbulence are modified by the horizontal temperature difference in time scales comparable to couple of circulation time scale of the LSCs.