Influence of viscoelasticity and unsteady friction of pipeline on surge tank oscillations in fast transient flows

This work presents a numerical study of a fast transient event in a pipeline system connected to a surge tank to attenuate high pressure waves, considering the viscoelastic effect of the pipe-wall and the unsteady friction separately. The momentum and continuity equations are solved by method of characteristic (MOC). The unsteady friction influence is investigated in both laminar and smooth wall turbulent flows. The effect of viscoelasticity of pipeline on pressure head at the downstream valve and the surge tank oscillations is investigated. In addition, via altering the location of the surge tank connected to the pipeline, the variation of the viscoelasticity effect on the surge tank oscillations is studied. The results show the more the distance between the surge tank and the downstream end is, the more the damping influence by viscoelasticity will be observed. In the last section, a reversed halfcone surge tank is used and the numerical results are compared with those deduced for a constant section area surge tank.

Keywords:

Waterhammer , viscoelasticity , unsteady friction , surge tank , liquid level oscillation