Evaluation of unsteady flow resistances by quasi-2D or 1D models

This note considers the evaluation of resistances in unsteady flow by means of a 1D unsteady friction model. The model is applied for the case of a water hammer, both in a single gravity pipeline and in a single pumped pipeline. Comparisons with experimental results show that the model does not predict the exact shape of the oscillation, but it gives, with high precision, the maximums and minimums of the pressure head oscillation if correct values of the parameter of the model are used. Because experimental evaluations can be made only for a few cases and can give rise to very different values depending on experimental conditions, the sensitivity of the model to physical and numerical parameters that influence the phenomenon is examined by comparison with the results of a quasi-2D model previously proposed.