The flow pattern created by a pitched blade turbine was calculated using a sliding I mesh method for various Reynolds numbers, mostly in the laminar regime. This method allows flow pattern calculations without the use of any experimental boundary conditions. The results compared favourably with experimental data obtained by laser-Doppler velocimetry. At low Reynolds number, the impeller creates a radial flow pattern rather than axial and the pumping number decreases with decreasing Reynolds number. It is concluded that the sliding mesh method is suitable for the prediction of flow patterns in stirred tanks.