Steady velocity estimates for the core fluid make possible new input data to the boundary layer equations that describe a flow field at the core-mantle boundary (CMB). Low valued estimates of the core fluid viscosity are adopted to solve the equations with large dimensions of 3000--6000 km or, alternatively, smaller scale lengths of 10 m of CMB topography which are used to make boundary layer thickness estimates of 163.6 and 0.2988 m for the large and small models repectively. The laminar velocity flow field within the layer thickness is calculated according to a numerical method developed for parabolic equations and is slower and thicker than boundary layers modelled in the same way for alternate atmospheric and benthic conditions. The model uses a zero pressure gradient and a flat rigid wall for the calculations to simplify this analysis. The surface topography at the CMB may alter the velocity field and produce turbulence. ¿American Geophysical Union 1991