The numerical study of natural convection in a square porous\ncavity saturated by a Newtonian fluid is presented in this study. The\nvertical walls are subjected to temperatures varying sinusoidally in time and\nphase opposition while the upper and lower horizontal walls are thermally\nadiabatic. Darcy model is used, it is also assumed the fluid studied is\nincompressible and obeys the Boussinesq approximation. The focus is on\nthe effect of the modulation frequency (10 ââ?°Â¤ Ãâ?° ââ?°Â¤ 100) and the Rayleigh\nnumber (10 ââ?°Â¤ Ra ââ?°Â¤ 1000) on the structure of the flow and transfer thermal.\nThe results show that the extremal stream functions (ÃË?max and ÃË?min), the\naverage Nusselt number at the hot (Tc) and cold (Tf) walls respectively\nNucmoy and Nufmoy are periodic and periods equal to that excitatory\ntemperatures to the range of parameters considered in this study. The\nresults show also that oscillatory heating causes the appearance of\nsecondary flow, whose amplification depends on the frequency of\nmodulation of the imposed temperature. The results are shown in terms of\nstreamlines and isotherms during a flow cycle.
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