Surface Roughness Effects in Near-Bed Turbulence: Implications to Sediment Entrainment

Papanicolaou, A. N.; Diplas, Panayiotis; Dancey, Clinton L.; Balakrishnan, Mahesh

doi:10.1061/(asce)0733-9399(2001)127:3(211)

Cited by 179 publications

(107 citation statements)

References 28 publications

Supporting

Mentioning

105

Contrasting

Order By: Relevance

“…Using hydrogen bubble visualization technique, Best (1992) attempted to link the sweeps with sediment entrainment and bed defect. The studies of Krogstad et al (1992) and Papanicolaou et al (2001) provided further evidence that the bed-packing conditions in gravel bed streams affect the turbulence characteristics and, in turn, sediment entrainment. Also, the quadrant analysis by Papanicolaou et al (2001) showed that the ratio of the Reynolds shear stress to the streamwise turbulence intensity is smaller in the low-density packed beds than in the densely packed beds.…”

Section: Introductionmentioning

confidence: 86%

“…The studies of Krogstad et al (1992) and Papanicolaou et al (2001) provided further evidence that the bed-packing conditions in gravel bed streams affect the turbulence characteristics and, in turn, sediment entrainment. Also, the quadrant analysis by Papanicolaou et al (2001) showed that the ratio of the Reynolds shear stress to the streamwise turbulence intensity is smaller in the low-density packed beds than in the densely packed beds. Hence, the condition of the entrainment threshold based on the time-averaged bed shear stress criterion may give lower values, especially for the low-density packed beds.…”

Section: Introductionmentioning

confidence: 86%

See 1 more Smart Citation

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

2011

View full text Add to dashboard Cite

This experimental study is devoted to quantification of the near-bed turbulence characteristics at an entrainment threshold of noncohesive sediments. Near the bed, the departure in the distributions of the observed time-averaged streamwise velocity from the logarithmic law is more for immobile beds than for entrainment-threshold beds. In the Reynolds shear stress distributions, a damping that occurs near the bed for sediment entrainment is higher than that for immobile beds. Quadrant analysis reveals that in the near-bed flow zone, ejections and sweeps on immobile beds cancel each other, giving rise to the outward interactions, whereas sweeps are the dominant mechanism toward sediment entrainment. The bursting duration for entrainment-threshold beds is smaller than that for immobile beds. On the other hand, the bursting frequency for entrainment-threshold beds is larger than that for immobile beds. The third-order correlations indicate that during sediment entrainment, a streamwise acceleration associated with a downward flux and advection of streamwise Reynolds normal stress is prevalent. The streamwise and the downward vertical fluxes of turbulent kinetic energy (TKE) increase with sediment entrainment. The TKE budget proves that for sediment entrainment, the pressure energy diffusion changes drastically to a negative magnitude, indicating a gain in turbulence production.

show abstract

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 86%

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

2011

View full text Add to dashboard Cite

show abstract

“…A similar analogy in the linkage between large-and small-scale processes exist in turbulent flows. For example, large-scale flow structures such as macro-eddies that scale with reach depth and bulk velocity have been shown to affect the frequency of occurrence of smaller eddies (known as the cascade process) that are responsible for the sporadic movement of the bed surface and the overall reorganization of the bed structure (Cantwell, 1981;Jain, 1991;Papanicolaou et al, 2001). From a sediment transport perspective, reach-scale interactions such as those between sediment supply and river capacity also have a large impact on the local bed structure and, hence, flow-field characteristics (Dietrich et al, 1989;Hassan and Church, 2000).…”

Section: Methodological Frameworkmentioning

confidence: 99%

Occurrence of cluster microforms in mountain rivers

Strom

Papanicolaou

2008

Earth Surf Processes Landf

Self Cite

View full text Add to dashboard Cite

The occurrence of cluster microforms in natural rivers is examined using data collected from three mountain streams. The study was conducted under the premise that the occurrence of clusters is strongly tied to local reach-scale conditions, and that prediction of clustered sites therefore can be made through identification of particular reach conditions that are conducive to cluster development. For the study, reach-scale variables were measured at 50 sites and the presence or absence of clusters at each of these sites was recorded. A statistical analysis using logistic regression was performed to examine the correlation between the occurrence of clusters and various combinations of reach-scale parameters. It was found that clustering was best predicted by the bankfull channel width scaled with the d 84 of the bed sediment, w/d 84 , and the non-dimensional parameter wQ 2 /gd 6 84 . It is thought that these variables work best at predicting the presence of clusters because they are descriptive of the reach hydraulic and sedimentary conditions and work well at discriminating between reach morphology types. It was found that clustering was most strongly tied to riffle-pool type reaches. Observations from this study suggest that clusters can be described as bed features that form out of the structural organization of grains in cobble-size sediment within depositional mountain reaches, for which the majority of the sediment can become mobilized by yearly peak flows.

show abstract

“…Several other studies have attempted to gather evidence to correlate turbulent events to the grain initial movement. Some authors have stated that the pickup of sediments was found to be highly correlated to the instantaneous value of the streamwise velocity [Williams et al, 1989;Nelson et al, 1995;Papanicolaou et al, 2001;Schmeeckle and Nelson, 2003]. However, in all these studies, apart from Papanicolaou et al [2001], no direct observations were made between the fluid velocities and grain motion.…”

Section: Introductionmentioning

confidence: 99%

Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements

Bottacin‐Busolin

Tait

Marion

et al. 2008

Water Resources Research

View full text Add to dashboard Cite

[1] Experiments were carried out using a mobile gravel bed placed in a tilting flume with a modified particle image velocimetry (PIV) system. Individual grain movements were surveyed using data from time series of images. Near-bed velocity flow field measurements were made simultaneously above the same area of the sediment surface by applying cross-correlation techniques to the collected plan view images. Statistics of grain motions were collected through a semiautomatic procedure. Significant changes in the flow field were observed in the proximity of the entrained or deposited particles. A strong correlation is shown between the changes in the local streamwise and lateral velocity and the movement of the grains. The theory of Grass is revisited and developed based on the experimental results. The probability distribution of individual grain resistance has been derived from the statistics of the near-bed velocity field and of the entrainment risk.Citation: Bottacin-Busolin, A., S. J. Tait, A. Marion, A. Chegini, and M. Tregnaghi (2008), Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements, Water Resour. Res., 44, W09419,

show abstract

Surface Roughness Effects in Near-Bed Turbulence: Implications to Sediment Entrainment

Cited by 179 publications

References 28 publications

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

Near-Bed Turbulence Characteristics at the Entrainment Threshold of Sediment Beds

Occurrence of cluster microforms in mountain rivers

Probabilistic description of grain resistance from simultaneous flow field and grain motion measurements

Contact Info

Product

Resources

About