Experimental and numerical study on transient air–water mixing flows in viscoelastic pipes

ABSTRACT

Air–water mixing flows are commonly formed in pressurized water supply pipes due to dissolved air from the water under low pressure conditions, and air injected through system controls and associated valves and pumps. This paper investigates transient behaviours of air–water mixing flows in viscoelastic pipes through laboratory experimental tests, numerical modelling and theoretical analysis. Two numerical schemes – the discrete vaporous cavity model (DVCM) and the discrete gas cavity model (DGCM), which are firstly calibrated and validated by the experimental data gained in this study, are adopted for comparative study for their validity and accuracy for modelling transient air–water mixing flows in viscoelastic pipes. With the validated model, the results of systematic analysis show that the effect of pipe-wall viscoelasticity on transient amplitude damping decreases with the increase of air content, and the frequency shifting rate of viscoelastic effect is negligible in comparison with that of air content.

Keywords:

• Air content
• air–water mixing flow
• transients
• unsteady friction
• viscoelasticity

Acknowledgments

I would like to express my gratitude to all those who helped me do the experiments again and again in Heilongjiang Institute of Construction Technology.

ORCID

Huan-Feng Duan http://orcid.org/0000-0002-9200-904X

Additional information

Funding

This work was financially supported by the Hong Kong Research Grants Council (RGC) [grants 25200616, 15201017 and T21-602/15-R], Hong Kong Polytechnic University [grants 1-ZVCD and 1-ZVGF], and National Natural Science Foundation of China [grant 51178141].