scholarly journals Effect of Sediment Supply on Morphodynamics of Free Alternate Bars: Insights from Hydrograph Boundary Layer

Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3437
Author(s):  
Huang Dai ◽  
Toshiki Iwasaki ◽  
Yasuyuki Shimizu
Keyword(s):  
Boundary Layer ◽  
Sediment Supply ◽  
Negligible Effect ◽  
River Morphology ◽  
Mobile Bed ◽  
Supply Condition ◽  
Alternate Bars ◽  
Limited Length ◽  
Dimensional Simulation ◽  
Specific Impact

Sediment supply plays an essential role in river morphology. However, the specific impact of sediment supply on river morphology is not apparent. According to the hydrograph boundary layer (HBL) concept, upstream riverbed changes caused by the imbalance between sediment supply and the capacity can propagate only a limited length and have a negligible effect on the riverbed beyond such a short length. We performed a two-dimensional morphodynamic calculation to test the concept of HBL, which was proposed under a one-dimensional simulation, meaning that the concept of HBL is still valid for plane changes in river morphology. We employed an unsteady flow with equilibrium or constant sediment supply in a straight, modeled gravel-bedded channel with an unerodible bank to simulate alternate bar morphodynamics. The results show that regardless of the sediment supply condition, the alternate bar features formed downstream of the HBL are considerably similar. This suggests that sediment disturbance at the upstream end has a negligible effect on the mobile-bed dynamic processes, including alternate bar formation and development downstream of the HBL.

Direct simulation of evolution and control of three-dimensional instabilities in attachment-line boundary layers

1995 ◽  
Vol 291 ◽  
pp. 369-392 ◽  
Author(s):  
Ronald D. Joslin
Keyword(s):  
Boundary Layer ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Computationally Efficient ◽  
Simulation Results ◽  
Dimensional Simulation ◽  
Attachment Line

The spatial evolution of three-dimensional disturbances in an attachment-line boundary layer is computed by direct numerical simulation of the unsteady, incompressible Navier–Stokes equations. Disturbances are introduced into the boundary layer by harmonic sources that involve unsteady suction and blowing through the wall. Various harmonic-source generators are implemented on or near the attachment line, and the disturbance evolutions are compared. Previous two-dimensional simulation results and nonparallel theory are compared with the present results. The three-dimensional simulation results for disturbances with quasi-two-dimensional features indicate growth rates of only a few percent larger than pure two-dimensional results; however, the results are close enough to enable the use of the more computationally efficient, two-dimensional approach. However, true three-dimensional disturbances are more likely in practice and are more stable than two-dimensional disturbances. Disturbances generated off (but near) the attachment line spread both away from and toward the attachment line as they evolve. The evolution pattern is comparable to wave packets in flat-plate boundary-layer flows. Suction stabilizes the quasi-two-dimensional attachment-line instabilities, and blowing destabilizes these instabilities; these results qualitatively agree with the theory. Furthermore, suction stabilizes the disturbances that develop off the attachment line. Clearly, disturbances that are generated near the attachment line can supply energy to attachment-line instabilities, but suction can be used to stabilize these instabilities.

scholarly journals Vertical distribution of Skewness and asymmetry in a boundary layer on a mobile bed. Experiment andk-ωmodel comparison

2014 ◽  
pp. 88-94 ◽  
Author(s):  
Leandro Suarez ◽  
Eric Barthelemy ◽  
Céline Berni ◽  
Julien Chauchat ◽  
Hervé Michallet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Mobile Bed

Study of Possibility of Simulation of Thick Turbulent Boundary Layer on a Flat Plate of Limited Length

2012 ◽  
Vol 7 (3) ◽  
pp. 44-56
Author(s):  
Vladimir Kornilov
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flat Plate ◽  
Effective Means ◽  
Leading Edge ◽  
Circular Cylinders ◽  
Mean Velocity ◽  
Velocity Scale ◽  
Limited Length ◽  
Fluctuation Boundary

The experiments directed to the study of possibility of simulation of thick equilibrium (according to Clauser) incompressible turbulent boundary layer on a flat plate of limited length have been performed. It is shown that the artificial generators manufactured from circular cylinders (pins) of adjustable height h, which were mounted normal to the wall in a staggered order in two rows in х in vicinity of the plate leading edge are quite effective means of artificial boundary layer thickening. In most cases both the averaged and fluctuation boundary-layer characteristics at a downstream distance about 530 cylinder diameters have values typical for naturally-developed turbulent boundary layer. Mean velocity profiles in the artificially thickened boundary layer taken in wall-law variables are approximated with a good accuracy by the wellknown velocity law valid for canonic boundary layer and they are generalized by a unified dependence using empirical velocity scale

scholarly journals Pattern formation and coarsening dynamics in three-dimensional convective mixing in porous media

2013 ◽  
Vol 371 (2004) ◽  
pp. 20120355 ◽  
Author(s):  
Xiaojing Fu ◽  
Luis Cueto-Felgueroso ◽  
Ruben Juanes
Keyword(s):  
Boundary Layer ◽  
Pattern Formation ◽  
Cellular Network ◽  
Gravitational Instability ◽  
Three Dimensional ◽  
Concentration Field ◽  
Convective Mixing ◽  
Long Term Storage ◽  
Diffusive Boundary ◽  
Dimensional Simulation

Geological carbon dioxide (CO 2 ) sequestration entails capturing and injecting CO 2 into deep saline aquifers for long-term storage. The injected CO 2 partially dissolves in groundwater to form a mixture that is denser than the initial groundwater. The local increase in density triggers a gravitational instability at the boundary layer that further develops into columnar plumes of CO 2 -rich brine, a process that greatly accelerates solubility trapping of the CO 2 . Here, we investigate the pattern-formation aspects of convective mixing during geological CO 2 sequestration by means of high-resolution three-dimensional simulation. We find that the CO 2 concentration field self-organizes as a cellular network structure in the diffusive boundary layer at the top boundary. By studying the statistics of the cellular network, we identify various regimes of finger coarsening over time, the existence of a non-equilibrium stationary state, and a universal scaling of three-dimensional convective mixing.

scholarly journals Impacts of Sand and Gravel Quarrying on the Stream Channel and Surrounding Environment

2017 ◽  
Vol 4 (1) ◽  
pp. 7-12
Author(s):  
Maharabam Anjali Devi ◽  
Lunghim Rongmei
Keyword(s):  
Remote Sensing ◽  
Remote Sensing And Gis ◽  
River Channel ◽  
Natural Process ◽  
Sediment Supply ◽  
River Morphology ◽  
Stream Channel ◽  
Gravel Mining ◽  
Surrounding Environment ◽  
Sand And Gravel

The longtime sustainability of river channel in the natural process depends on the gradient, volume of water, sediment supply and deposition in the river. Naturally, rivers maintain balance of river channel in all stage of the cycle of erosion. However, human activity mainly sand and gravel mining frequently disturb the balance that has much impact on the river morphology. The Imphal River between Motbung to Awang Leikinthabi is one of the worse sand and gravel-querying regions in Manipur. Hence, the main aim of this paper is to assess the impacts of querying on riverine landform and surrounding environment by using Remote Sensing and GIS.

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