Analysis of the stirring process of water bath contained in a rotating cylindrical vessel with particle imaging velocimetry

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