Enhancement of mixed convection heat transfer in a square cavity via a freely moving elastic ring

A freely moving elastic ring is used to enhance mixed convection heat transfer in a two-dimensional square cavity with three different Richardson (Ri) numbers of 0.1, 1.0, and 10. The multiple-relaxation time lattice Boltzmann method combined with the immersed boundary method is employed to simulate the mixed convection heat transfer and its interaction with the elastic ring in the cavity. Two different thermal conditions for the elastic ring, i.e., with and without thermal interaction, are considered. The results are given in terms of streamlines, isotherms, temperature distribution, and Nusselt (Nu) number. It was found that at the steady state, the ring accords to one of the streamlines in the cavity. In addition, for each investigated case, the Nu number decreases as the Ri number increases. Besides, the presence of the ring leads to a much higher heat transfer (Nu number) and a much earlier steady state as compared to the case with no ring. Finally, the values of the Nu number for both thermal conditions of the ring are about the same being slightly higher for the ring with thermal interaction.