The instantaneous velocity of laminar flow in a water bath contained in a cylindrical vessel, being initially at rest and then suddenly set in rotation, was measured with particle imaging velocimetry (PIV). The period from the start of rotation to the moment at which the flow in the bath reaches steady state is defined as the flow establishment time. The results for the establishment time were compared with previous empirical equations derived on the basis of velocity measurements with laser Doppler velocimetry (LDV), and an applicable range of the equations was evaluated. The measured values of the flow establishment time were underestimated by the equations. This is because the equations were obtained in a higher Reynolds number range. An empirical equation for the flow establishment time was newly proposed.
