Abstract: The traditional quasi-steady friction model can not be accurately described the real transient problems in transient pipe flow. The conventional quasi-steady friction model and the historical approaches proposed for improving the numerical modeling of transient events was summarized in the paper. The solutions of the several unsteady friction models with the well-known method of characteristics were presented. The models were verified for turbulent flows and the unsteady friction models indicated better agreement between measured and computed pressure heads than the conventional quasi-steady friction model. And finally, the more accurate unsteady friction models were applied to simulate transient pipe flow in other pipelines such as crude oil and product oil pipelines.

Key words: liquid, pipeline, transients, water hammer, friction losses, unsteady friction losses