**ABSTRACT**

The present numerical investigation aims to analysis the enhancement heat transfer in the nanofluid filled-complex geometries saturated with a partially layered porous medium. The vertical walls of the cavity are taken as complex wavy geometries. The horizontal walls of the cavity are flat with insulated temperature. The complex wavy cavity is filled with a nanofluid and the upper half of the wavy cavity is saturated with the porous medium. In the analysis, the governing equations are formulated for natural convection under the Boussinesq approximation in various environments including pure-fluid, nanofluid, and porous medium. In this investigation, the effects of the Rayleigh number (103≤Ra≤105), Darcy parameter (10−6≤ Da ≤10−3), thermophoresis parameter (0.1≤ Nt ≤0.5), nanofluid buoyancy ratio (0.1≤ Nr ≤0.5), Brownian motion parameter (0.1≤Nb≤0.5), inclination angle (0°≤ γ ≤90°), and geometry parameters α1 and R have been studied on the streamlines, temperature, nanoparticles volume fraction, local Nusselt number Nu and the local Sherwood number Sh. It is found that, the performance of the heat transfer can be improved by adjusting the geometry parameters of the wavy surface. Overall, the results showed that the nanofluid parameters enhance the convection heat transfer and the obtained results provide a useful insight for enhancing heat transfer in two separate layers of nanofluid and porous medium inside complex-wavy cavity.

**KEYWORDS**

PAPER SUBMITTED: 2018-12-18

PAPER REVISED: 2019-04-05

PAPER ACCEPTED: 2019-04-11

PUBLISHED ONLINE: 2019-05-12

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