The objective of the work presented here was the development of a method of modeling the effect of an impeller on the velocity distribution in a stirred vessel. The developed model makes it possible to numerically investigate the flow field almost independently of any experimental data. The starting point was a force balance around an impeller blade, which took into consideration the lift and drag forces. The obtained volume forces were circumferentially averaged in the impeller region. The calculations were carried out time-averaged for the case of a pitched blade impeller. The results were compared with experimental data which were obtained by laser Doppler anemometry. The comparison of the axial velocity components shows a good agreement between numerical and experimental data. Furthermore some characteristic integral values were calculated, which demonstrate the efficiency of the impeller.