Proper orthogonal decomposition of thermally-induced flow structure in an enclosure with alternately active localized heat sources.

The paper presents the structure of buoyancy-driven flow occurring in an enclosure with two alternately active discrete heat sources. For the analysis of the mixing of the fluid layer and its effect on heat transfer process, the flow information has been presented both in time and spectral domain. The inherent dynamics is also studied using the proper orthogonal decomposition (POD). POD technique is used here to assess the energy content in the different modes and the related coherent structures of flow considering different Rayleigh numbers (Ra = 103–106), switching frequencies (Z 1 with Z = 0.1–0.8) and air as working fluid of Prandtl number (Pr) of 0.71. The results reveal nonlinear characteristics of hydrodynamics and heat transfer at higher Ra for low frequency. Here, POD helps understanding the flow dynamics from information about the coherent structures of different energy modes.