Investigation on the stability of natural convection in an annular cavity with non-isothermal walls

• Published in: Experimental thermal and fluid science 2020-07, Vol.115, p.110053, Article 110053
• Main Authors: Sondur, Sneha, Mescher, Ann M.
• Format: Article
• Language: English
• Subjects: Air flow; Airflow; Bifurcations; Boundary conditions; Chaotic flow; Convection; Convection cells; Free convection; Instability; Intermittent flow; Natural convection; Non-isothermal walls; Periodic flow; Prandtl number; Quasi-chaotic flow; Quasi-periodic flow; Rayleigh number; Stability; Steady flow; Swirling; Unsteady flow; Walls
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2020.110053

•Experimental study of natural convection in non-isothermal annular cavity.•3D asymmetric oscillatory instability modes observed.•Frequency/amplitude of thermal oscillations mapped.•Routes to chaotic flow reported for different thermal boundary conditions.•Flow bifurcations observed by monitoring temperature data. The onset and nature of unsteady natural convection in a tall, closed annular cavity with non-isothermal walls is investigated experimentally. In the first of a sequence of experiments, thermal boundary conditions imposed on the inner and outer cylinders promote steady bi-cellular natural convection airflow inside the cavity. As the buoyant potential of the upper convection cell is increased, steady flow inside the cavity first bifurcates into mono-periodic flow and then follows a quasi-periodic route to chaotic flow. Similarly, when the buoyant potential of the lower convection cell is increased, steady flow bifurcates into mono-periodic flow and then follows an intermittent route to chaos. All of the observed unsteady airflows inside the annular cavity were three-dimensional, with all of the periodic flows exhibiting a gentle swirling motion in the azimuthal direction.