The aspiration of the present problem is to investigate numerically the 2D unsteady buoyancy convection of cold water near its highest density value in an inclined square porous enclosed space. Left sidewall temperature varies in sinusoidal manner whereas the opposing right sidewall is sustained with constant lower temperature. The walls along x axis and parallel to x axis are kept in adiabatic condition. The range of angle of inclination is considered from 0 degree to 90 degree. The finite volume method (FVM) was applied to portray all mathematical equations. The special outcome of inclination angle, Darcy number, maximum density parameter and porosity are obtained in the present study with the use of Brinkmann–Forchheimer extended Darcy model. The change in the angle of inclination is noteworthy in the structure and direction of the flow of the fluid. The bicellular structure of the fluid is identified because of the higher density effect.