A novel axial velocity profile integration method, obtained from ultrasonic perpendicular velocimetry, for flow estimation in curved tubes was validated. In an experimental set-up, physiologically relevant curved geometries and flows were considered. Axial velocity profile measurements were taken by applying particle imaging velocimetry-based methods to ultrasound data acquired by means of a linear array transducer positioned perpendicular to the axial velocity component. Comparison of the assessed asymmetric velocity profiles to computational fluid dynamics calculations showed excellent agreement. Subsequently, the recently introduced cos ?-integration method for flow estimation was compared to the presently applied poiseuille and womersley models. The average deviation between the cos ?-integration-based unsteady flow estimate and the reference flow was about 5%, compared to an average deviation of 20% for both the poiseuille and womersley approximation. Additionally, the effect of off-centre measurement was analysed for the three models. It was found that only for the cos ?-integration method, an accurate flow estimation is feasible, even when it is measured off centre.