Swirl Switching in bent pipes studied by numerical simulation

Philipp Schlatter, Lorenz Hufnagel, Jacopo Canton, Elia Merzari, Oana Marin, Ramis Orlu

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Turbulent flow through pipe bends has been extensively studied, but several phenomena still miss an exhaustive explanation. Due to centrifugal forces, the fluid flowing through a curved pipe forms two symmetric, counter-rotating Dean vortices. It has been observed, experimentally and numerically, that these vortices change their size, intensity and location in a quasi-periodic, oscillatory fashion, a phenomenon known as swirl-switching. These oscillations are responsible for failure due to fatigue in pipes, and their origin has been attributed to a recirculation bubble, disturbances coming from the upstream straight section and others. The present study tackles the problem by direct numerical simulations (DNS) of turbulent pipe flow at moderate Reynolds number, analysed, for the first time, with three-dimensional proper orthogonal decomposition (POD) in an effort to distinguish between the spatial and temporal contributions to the oscillations. The simulations are performed at a friction Reynolds number of about 360 with a divergence-free synthetic turbulence inflow, which is crucial to avoid the interference of low-frequency oscillations generated by a standard recycling method. Two different bends are considered, with curvature 0.1 and 0.3, preceded and followed by straight pipe segments. Our results indicate that a single low-frequency, three-dimensional POD mode is responsible for the swirl-switching. This mode represents a travelling wave, and was previously mistaken by 2D POD for two different modes. Low-order reconstruction clearly shows that the upstream turbulent flow does not play a role for the swirl-switching.

Original languageEnglish (US)
Title of host publication10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
PublisherInternational Symposium on Turbulence and Shear Flow Phenomena, TSFP10
ISBN (Electronic)9780000000002
StatePublished - Jan 1 2017
Event10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017 - Chicago, United States
Duration: Jul 6 2017Jul 9 2017

Publication series

Name10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
Volume2

Conference

Conference10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017
CountryUnited States
CityChicago
Period7/6/177/9/17

All Science Journal Classification (ASJC) codes

  • Atmospheric Science
  • Aerospace Engineering

Fingerprint Dive into the research topics of 'Swirl Switching in bent pipes studied by numerical simulation'. Together they form a unique fingerprint.

  • Cite this

    Schlatter, P., Hufnagel, L., Canton, J., Merzari, E., Marin, O., & Orlu, R. (2017). Swirl Switching in bent pipes studied by numerical simulation. In 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017 (10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017; Vol. 2). International Symposium on Turbulence and Shear Flow Phenomena, TSFP10.