Precise measurements of the Earth's rotation have led to estimates of energy dissipation near the core-mantle boundary, revealing a mismatch between the observed and theoretical values. This discrepancy suggests that studying the Earth's rotational motion can offer insights into its internal physical processes. Turbulence and surface roughness in the boundary layer have been proposed as potential mechanisms to explain the discrepancy. However, there is still room for improvement in quantifying these effects due to the lack of appropriate experimental or numerical results. To address this, we employ a local box model to numerically investigate the boundary layer. This approach, compared to a global spherical model, allows for the exploration of more extreme parameter regimes, providing insights into the influence of turbulence. Additionally, surface roughness is modeled by introducing undulations on the boundary to assess its impact on viscous dissipation.