 |
| Titel |
Secondary flow structures in large rivers |
| VerfasserIn |
H. Chauvet, O. Devauchelle, F. Métivier, A. Limare, E. Lajeunesse |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069700
|
|
|
|
|
|
| Zusammenfassung |
| Measuring the velocity field in large rivers remains a challenge, even with recent
measurement techniques such as Acoustic Doppler Current Profiler (ADCP). Indeed, due to
the diverging angle between its ultrasonic beams, an ADCP cannot detect small-scale flow
structures. However, when the measurements are limited to a single location for a sufficient
period of time, averaging can reveal large, stationary flow structures. Here we present
velocity measurements in a straight reach of the Seine river in Paris, France, where the
cross-section is close to rectangular. The transverse modulation of the streamwise velocity
indicates secondary flow cells, which seem to occupy the entire width of the river. This
observation is reminiscent of the longitudinal vortices observed in laboratory experiments
(e.g. Blanckaert et al., Advances in Water Resources, 2010, 33, 1062-1074). Although the
physical origin of these secondary structures remains unclear, their measured velocity is
sufficient to significantly impact the distribution of streamwise momentum. We
propose a model for the transverse profile of the depth-averaged velocity based on
a crude representation of the longitudinal vortices, with a single free parameter.
Preliminary results are in good agreement with field measurements. This model
also provides an estimate for the bank shear stress, which controls bank erosion. |
|
|
|
|
|
|