Letters to ESEX
Bridging the gap between turbulence and larger scales of flow motions in rivers
Article first published online: 10 FEB 2011
Copyright © 2011 John Wiley & Sons, Ltd.
Earth Surface Processes and Landforms
Volume 36, Issue 4, pages 563–568, April 2011
How to Cite
Marquis, G. A. and Roy, A. G. (2011), Bridging the gap between turbulence and larger scales of flow motions in rivers. Earth Surf. Process. Landforms, 36: 563–568. doi: 10.1002/esp.2131
- Issue published online: 10 MAR 2011
- Article first published online: 10 FEB 2011
- Manuscript Accepted: 13 DEC 2010
- Manuscript Revised: 9 DEC 2010
- Manuscript Received: 4 AUG 2010
- gravel-bed river;
Although flow turbulence in rivers is of critical importance to earth scientists, ecologists and engineers, its relations with larger flow scales are not well understood, thus leaving a fundamental gap in our knowledge. From an analysis of a long time series of the streamwise and vertical flow velocity fluctuations measured in a gravel-bed river, we show that the signature of the fundamental turbulent flow structures (e.g. ejections and sweeps) is embedded within increasingly larger flow scales in a self-similar manner. The imbrication of turbulent structures into large flow pulsations of flow acceleration and deceleration covers more than two-orders of magnitude from a few seconds to nearly 10 minutes. This property is explained by the clustering of turbulent events creating an emergent pattern at larger scales. The size of the larger flow pulsations scales with the spacing of the pools and riffles in the river. This implies a mutual adjustment between turbulence generation mechanisms and long pulsations of flow acceleration and deceleration controlled by the bed morphology. These results bridge a gap in our understanding of flows in rivers and offer a new perspective on the interactions between the turbulent flow with larger scales of flow motion that are critical for sediment transport, habitat selection and fish behaviour. Copyright © 2011 John Wiley & Sons, Ltd.