Friction–Frequency Dependence for Oscillatory Flows in Circular Pipe

Measured data of velocity changes in oscillatory flows (0.16–0.36Hz) are presented. The actual wall shear stresses obtained from these measurements are compared to calculated values based on steady flow relations and Zielke’s model. A new model for the prediction of the wall shear stress as a function of velocity and acceleration changes is introduced. The proposed model may be a suitable basis for the prediction of friction data for one-dimensional flow analysis under nonsteady conditions.