Turbulent characteristics and evolution of sheet flow in an alluvial channel with downward seepage

Patel, Mahesh; Deshpande, Vishal; Kumar, Bimlesh

doi:10.1016/j.geomorph.2015.07.042

Cited by 25 publications

(11 citation statements)

References 67 publications

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“…Earlier, Patel et al . () also observed higher streamwise velocities over a coarse sand bed with the application of seepage.…”

Section: Linkage Between Flow and Bedform Developmentsmentioning

confidence: 74%

“…In this regard, Patel et al . () also observed the evolution of a sheet layer because of increased RSS in the presence of seepage. Here, increase in time‐averaged velocities and RSS values as shown in Figure to initiate sediment transport, which may result in initiation of bedforms with the application of downward seepage.…”

Section: Linkage Between Flow and Bedform Developmentsmentioning

confidence: 80%

“…More details of the experimental setup and parabolic cross‐section bed profile can be found in Patel et al . ().…”

Section: Experimental Set Up and Data Acquisitionmentioning

confidence: 97%

“…In earlier experimental studies, effect of seepage through porous boundaries is substantial on the turbulent flow characteristics, for example, streamwise time‐average velocities were found to be increased in the zone close to the channel bed with the application of downward seepage (Oldenziel and Brink, ; Maclean, ; Chen and Chiew, ). Literature suggests that downward seepage causes increase in tractive stresses, leading to increase in sediment movement in alluvial channels (Watters and Rao, ; Willetts and Drossos, ; Maclean, ; Rao and Sitaram, ; Sreenivasulu et al ., ; Rao et al ., ; Cao and Chiew, ; Patel et al ., ). Very few studies have reported in the context of the effect of seepage on bedforms geometry, for example, Harrison () performed experiments and observed that the angle of the lee face of bedform increases under the influence of downward seepage.…”

Section: Introductionmentioning

confidence: 97%

“…Seepage, being an integral part of alluvial flow, is needed to understand the morphology and hydrodynamics of fluvial systems. In our previous study, extensive research regarding the influence of seepage on channel morphology and flow turbulence has been pursued (Patel et al ., ; Deshpande and Kumar, ), while the effect of different percentages of seepage on the flow structure and celerity of migrating bedforms have not been discussed over fine sand bed channels. Taking this deficit into consideration, the objectives of this study are to analyse the effect of downward seepage on turbulent flow structure, geometry of bedforms, and celerity of developing bedforms on a curvilinear cross‐section threshold alluvial channel.…”

Section: Introductionmentioning

confidence: 99%

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This study, using an experimental approach, focuses on the effect of downward seepage on a threshold alluvial channel morphology and corresponding turbulent flow characteristics. In all the experiments, we observed that the streamwise time-averaged velocities and Reynolds shear stresses were increased under the influence of downward seepage. Scales of eddy length and eddy turnover time were significantly increased with the application of downward seepage, leading to sediment transport and initiation of bedforms along the channel length. As the amount of seepage discharge increased, eddy length and turnover time were further increased, causing the development of larger bedforms. It was revealed that the geometry of bedforms was linked with the size of eddies. In this work, statistics of bedform dynamics are presented in terms of multi-scalar bedforms in the presence of seepage. These multi-scalar ubiquitous bedforms cast a potential impact on flow turbulence as well as stream bed morphology in channels. We used wavelet to analyse temporally lagged spatial bed elevation profiles that were obtained from a set of laboratory experiments and synchronized the wavelet coefficients with bed elevation fluctuations at different length scales. A spatial crosscorrelation analysis, based on the wavelet coefficients, was performed on these bed elevation datasets to observe the effect of downward seepage on the dynamic behaviour of bedforms at different length scales. It was found that celerity of bedforms reduced with increase in seepage percentage. Bedform celerity was best approximated by a probability density function such as Rayleigh distribution under varying downward seepage. Further, statistical analysis of physical parameters of bedforms ascertained that the reduction in bedform celerity was a result of increased bedform size.

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“…Earlier, Patel et al . () also observed higher streamwise velocities over a coarse sand bed with the application of seepage.…”

Section: Linkage Between Flow and Bedform Developmentsmentioning

confidence: 74%

Section: Linkage Between Flow and Bedform Developmentsmentioning

confidence: 80%

“…More details of the experimental setup and parabolic cross‐section bed profile can be found in Patel et al . ().…”

Section: Experimental Set Up and Data Acquisitionmentioning

confidence: 97%