Author(s): Raphael Frey; Michael Güdel; Jurg Dual; Thomas Staubli
Keywords: Frequency domain; impedance method; pipeline; polymer; viscoelasticity
Abstract: This research paper describes an experimental method and the corresponding theory which enables the characterization of small viscoelastic pipes. The experimental set-up is a reservoir–pipeline–oscillating-valve configuration, where valve opening and pressure just upstream of the valve were measured. This allows the extraction of pressure amplitude and phase at this point. This configuration can be analytically modelled in the frequency domain with help of the impedance method. The viscoelastic behaviour of the pipe is modelled with a multi-element Kelvin–Voigt model whose moduli are estimated with a least squares method to fit the recorded complex-valued pressure data with the modelled one. Extracting amplitude and phase of the pressure signal is doubling the amount of data which can be used in the estimation algorithm. This and the use of an analytical model provides a robust and fast method to calibrate the viscoelastic properties of a pipe in the frequency domain.