Pulsatile Turbulent Flow in Straight and Curved Pipes – Interpretation and Decomposition of Hot-Wire Signals

Abstract

Pulsatile turbulent flows in curved pipes at high Womersley and Reynolds numbers are prevalent in various components of internal combustion engines, in particular in the intake of the exhaust manifold. Despite their technological importance, there appears to be a lack of experimental data both with regard to straight and bent pipes. The present paper addresses this gap through phase-locked hot-wire anemometry measurements in a highly pulsatile turbulent flow through straight and bent pipes and compares the results with those obtained under steady flow conditions. The aim is to understand to some extent the effect of pulsations on the turbulent flow itself and for that purpose different decomposition methods are applied to the data in order to reveal the underlying turbulence from the pulsatile signal. Besides classical phase-averaging, also temporal filtering and singular value decomposition have been employed to investigate the decomposed turbulence statistics in terms of their pulsatile and turbulence contributions. Results show that—due to the large scale separation between the turbulence and pulsations—both decomposition techniques provide similar results and highlight, that the statistics from the turbulent part of the pulsatile flow resemble those of the steady one.