Influence of nonlinear turbulent friction on the system frequency response in transient pipe flow modelling and analysis

Abstract

The system frequency response (SFR) based method has been widely developed and applied for the modelling of transient pipe flow and the assessment of pipeline system conditions. The linearization assumption is commonly imposed for the nonlinear turbulent friction term in the SFR model. Previous studies have demonstrated the impact of the linearization approximation on the accuracy of SFR-based modelling and analysis. This paper aims to improve the traditional SFR-based method by incorporating the nonlinear component of the friction term in a two-step analytical extension of the SFR expression. Numerical comparisons with the method of characteristic (MOC) highlight the improved accuracy that the extended SFR result provides over the traditional approach under various flow conditions.

Keywords:

• Nonlinear turbulent friction
• relative importance
• system frequency response
• transfer matrix
• transient

ORCID

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

Additional information

Funding

This research was supported by the research grants from: (1) the Hong Kong Polytechnic University (HKPU) under the projects no. 1-ZVCD, no. 1-ZVGF and no. 3-RBAB; and (2) Research Grants Council, University Grants Committee; the Hong Kong Research Grant Council (RGC) under the projects no. T21-602/15-R, no. 25200616 and no. 15201017.