Spatial averaging over a variable volume and its implications for simulation of open channel flows over permeable beds

A. Bello, D. Pokrajac, A. Leonardi

Research output: Chapter in Book/Report/Conference proceedingPublished conference contribution

Abstract

Double-averaging methodology is commonly used for investigating spatially heterogeneous flows such as boundary layer flows over rough permeable walls, for example natural streams flowing over gravel beds. However, spatial averaging volume suitable for open channel flows over rough beds is very thin in the bed-normal direction, whereas for porous media flows within the bed, similar length in all three directions is more ideal. This scale mismatch can be addressed by allowing the averaging volume to vary in space, so that its size can be adjusted to the physical characteristics of particular flow regions. This paper revisits the double-averaged continuity and momentum equations for a spatially variable averaging volume derived by Pokrajac & de Lemos (2015). Compared to the conventional double-averaged continuity and Navier-Stokes equations, the new equations contain an additional term which accounts for the spatial variation of the averaging volume. The new averaging procedure is illustrated using an example from the literature, which involves a 3-dimensional Large Eddy Simulation (LES) of open channel flow over a porous bed consisting of 5 layers of uniform size spheres.

Original languageEnglish
Title of host publicationRiver Flow 2020 - Proceedings of the 10th Conference on Fluvial Hydraulics
EditorsWim Uijttewaal, Mario J. Franca, Daniel Valero, Victor Chavarrias, Claudia Ylla Arbos, Ralph Schielen, Ralph Schielen, Alessandra Crosato
PublisherCRC Press/Balkema
Pages13-21
Number of pages9
ISBN (Electronic)9780367627737
Publication statusPublished - 2020
Event10th Conference on Fluvial Hydraulics, River Flow 2020 - Virtual, Online, Netherlands
Duration: 7 Jul 202010 Jul 2020

Publication series

NameRiver Flow 2020 - Proceedings of the 10th Conference on Fluvial Hydraulics

Conference

Conference10th Conference on Fluvial Hydraulics, River Flow 2020
Country/TerritoryNetherlands
CityVirtual, Online
Period7/07/2010/07/20

Bibliographical note

Publisher Copyright:
© 2020 Taylor & Francis Group, London

Keywords

  • Double-averaging
  • Fluid-Porous interface
  • Large Eddy Simulation (LES)
  • Variable averaging volume

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