TY - JOUR
T1 - The role of velocity, pressure, and bed stress fluctuations in bed load transport over bed forms
T2 - Numerical simulation downstream of a backward-facing step
AU - Schmeeckle, Mark
N1 - Publisher Copyright:
© 2014 Author(s).
PY - 2015/2/9
Y1 - 2015/2/9
N2 - Bed load transport over ripples and dunes in rivers exhibits strong spatial and temporal variability due to the complex turbulence field caused by flow separation at bedform crests. A turbulence-resolving flow model downstream of a backward-facing step, coupled with a model integrating the equations of motion of individual sand grains, is used to investigate the physical interaction between bed load motion and turbulence downstream of separated flow. Large bed load transport events are found to correspond to low-frequency positive pressure fluctuations. Episodic penetration of fluid into the bed increases the bed stress and moves grains. Fluid penetration events are larger in magnitude near the point of reattachment than farther downstream. Models of bed load transport over ripples and dunes must incorporate the effects of these penetration events of high stress and sediment flux.
AB - Bed load transport over ripples and dunes in rivers exhibits strong spatial and temporal variability due to the complex turbulence field caused by flow separation at bedform crests. A turbulence-resolving flow model downstream of a backward-facing step, coupled with a model integrating the equations of motion of individual sand grains, is used to investigate the physical interaction between bed load motion and turbulence downstream of separated flow. Large bed load transport events are found to correspond to low-frequency positive pressure fluctuations. Episodic penetration of fluid into the bed increases the bed stress and moves grains. Fluid penetration events are larger in magnitude near the point of reattachment than farther downstream. Models of bed load transport over ripples and dunes must incorporate the effects of these penetration events of high stress and sediment flux.
UR - http://www.scopus.com/inward/record.url?scp=84941353371&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84941353371&partnerID=8YFLogxK
U2 - 10.5194/esurf-3-105-2015
DO - 10.5194/esurf-3-105-2015
M3 - Article
AN - SCOPUS:84941353371
SN - 2196-6311
VL - 3
SP - 105
EP - 112
JO - Earth Surface Dynamics
JF - Earth Surface Dynamics
IS - 1
ER -