Interaction between curvature-driven width oscillations and channel curvature in evolving meander bends

2019 ◽  
Vol 876 ◽  
pp. 985-1017 ◽  
Author(s):  
F. Monegaglia ◽  
M. Tubino ◽  
G. Zolezzi
Keyword(s):  
Channel Width ◽  
Feedback Process ◽  
Remotely Sensed Data ◽  
Meandering River ◽  
Aspect Ratios ◽  
Meander Bends ◽  
Channel Curvature ◽  
Curvature Driven ◽  
Additional Equation ◽  
Insight Into

We study the morphodynamics of channel width oscillations associated with the planform development of river meander bends. With this aim we develop a novel planform evolution model, based on the framework of the classical bend theory of river meanders by Ikeda et al. (J. Fluid Mech., vol. 112, 1981), that accounts for local width changes over space and time, tied to the local hydro-morphodynamics through a two-way feedback process. We focus our attention on ‘autogenic’ width variations, which are forced by flow nonlinearities driven by channel curvature dynamics. Under the assumption of regular, sinusoidal width and curvature oscillations, we obtain a set of ordinary differential equations, formally identical to those presented by Seminara et al. (J. Fluid Mech., vol. 438, 2001, pp. 213–230), with an additional equation for the longitudinal oscillation of the channel width. The proposed approach gives insight into the interaction between autogenic width variations and curvature in meander development and between forcing and damping effects in the formation of width variations. Model outcomes suggest that autogenic width oscillations mainly determine wider-at-inflection meandering river patterns, and affect their planform development particularly at super-resonant aspect ratios, where the width oscillation reaches its maximum and reduces meander sinuosity and lateral floodplain size. The coevolution of autogenic width oscillation and curvature occurs through temporal hysteresis cycles, whereby the peak in channel curvature lags behind that of width oscillation. Width oscillation amplitudes predicted by the model are consistent with those extracted from remotely sensed data.

Bend theory of river meanders with spatial width variations

2011 ◽  
Vol 681 ◽  
pp. 311-339 ◽  
Author(s):  
ROSSELLA LUCHI ◽  
GUIDO ZOLEZZI ◽  
MARCO TUBINO
Keyword(s):  
Perturbation Expansion ◽  
Potential Interaction ◽  
Channel Width ◽  
Meandering Streams ◽  
Meandering River ◽  
Longitudinal Modes ◽  
Meandering Channels ◽  
Aspect Ratios ◽  
Meander Bends ◽  
Averaged Model

The present work revisits the classical, uniform-width bend theory with the aim to understand whether and how spatial width oscillations can affect the process of linear bend stability that initiates meander planform evolution. Although longitudinal oscillations of channel width are common along many meandering streams, little investigation of their properties and dynamic effects has been pursued so far. The theory therefore accounts for width variations as a geometrical forcing in a depth-averaged model of meander morphodynamics by assuming the potential interaction with the classical curvature forcing effect. A first quantification of width variations is made by referring to a freely evolving meandering river, which shows that the dimensionless amplitude of width variations is a ‘small’ parameter with comparable magnitude to that of curvature variations, thus suggesting the use of a two-parameter perturbation expansion. Moreover, it is reasonable to assume that channel width oscillates in space with a double frequency relative to curvature, which implies that one nonlinear interaction between the two forcing effects is enough to reproduce the effect of spatial width variations on the process of bend stability. Overall, width variations consistently promote the instability of shorter bends with respect to meanders with uniform width: on average, this predicted tendency is supported by analysis of field data referring to hundreds of natural meander bends. The effect on meander wavelength selection depends on the location of the widest section relative to the bend apex. Under typical formative conditions of gravel-bed rivers, with large-enough channel aspect ratios, two distinct most unstable longitudinal modes develop. Such behaviour is absent when the width is uniform, and suggests a mechanistic interpretation for the reach-scale occurrence of chute cutoffs that can be observed more frequently in wider-at-bends than in equiwidth meandering channels.

Upstream and downstream morphodynamic influence in simulated and real meandering rivers

2021 ◽  
Author(s):  
Hossein amini ◽  
Guido Zolezzi ◽  
Federico Monegaglia ◽  
Emanuele Olivetti ◽  
Marco Tubino
Keyword(s):  
Migration Rate ◽  
Machine Learning Techniques ◽  
Stochastic Gradient Descent ◽  
Support Vector ◽  
Lateral Migration ◽  
Remotely Sensed Data ◽  
Meandering Rivers ◽  
Meandering River ◽  
Migration Rates ◽  
Meander Migration

<p>This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.</p><p>References </p><p>1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183–211. https://doi.org/10.1017/S002211200100427X</p><p>2- Monegaglia, F., Zolezzi, G., Güneralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171–186). https://doi.org/10.1016/j.envsoft.2018.03.028</p><p>3- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137–5157). https://doi.org/10.1002/2017wr020726</p><p>4- Benozzo, D.,  Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics. </p><p>https://doi.org/10.3389/fninf.2017.00068 </p><p>5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216. </p><p>https://arxiv.org/abs/2011.04216</p>

scholarly journals Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data

2018 ◽  
Vol 105 ◽  
pp. 171-186 ◽  
Author(s):  
Federico Monegaglia ◽  
Guido Zolezzi ◽  
Inci Güneralp ◽  
Alexander J. Henshaw ◽  
Marco Tubino
Keyword(s):  
Remotely Sensed ◽  
Automated Extraction ◽  
Remotely Sensed Data ◽  
Meandering River

Computational Analysis of Fiber Dynamics in Human Nasal Cavity

2020 ◽  
Author(s):  
Jiawei Ma ◽  
Jiyuan Tu ◽  
Lin Tian ◽  
Goodarz Ahmadi
Keyword(s):  
Nasal Cavity ◽  
Transport Processes ◽  
Upper Respiratory Tract ◽  
Governing Equations ◽  
Aspect Ratios ◽  
Model Predictions ◽  
Fiber Dynamics ◽  
Upper Respiratory ◽  
Rotational Motions ◽  
Insight Into

Abstract Elongated particles, such as asbestos and mineral fibers, are considered severe inhalation hazards due to their ability to penetrate into the deep lung. Frequently the dynamic behavior of the fibrous particles is attributed to their unique needle-like geometry. Therefore, understanding the interactions of the inhaled elongated particles with the airflow environment is of great significance. In this study, the transport and deposition of elongated micro-fibers in a realistic human nasal cavity is investigated numerically. The motion of the micro-fiber is resolved by solving the system of equations governing its coupled translational and rotational motions. The governing equations included the drag, the hydrodynamic torques that were evaluated using the Jeffrey model. The influence of the shear lift force was also included in these simulations. The no-slip wall boundary condition for airflow in the airways was used. Since the surface of airways is covered with mucus, when a fiber touches the surface, it was assumed to be deposited with no rebound. The study allows a close look at the non-spherical particle-flow dynamics with respect to the translation, rotation, coupling, and how the rotation affects the particle’s macroscopic transport and deposition properties. A series of simulations for different microfiber diameters and aspect ratios were performed. The simulation results are compared with the existing experimental data, and earlier computational model predictions and good agreements were obtained. The present study also seeks to provide additional insight into the transport processes of microfibers in the upper respiratory tract.

scholarly journals The Spatial Distribution of Bed Sediment on Fluvial System: A Mini Review of the Aceh Meandering River

2016 ◽  
Vol 5 (2) ◽  
Author(s):  
Muhammad Irham
Keyword(s):  
Spatial Distribution ◽  
Bed Load ◽  
Sieve Analysis ◽  
Left Bank ◽  
Fluvial System ◽  
Dynamic Interactions ◽  
Meandering River ◽  
River Bed ◽  
Meander Bends ◽  
Mechanical Weathering

Dynamic interactions of hydrological and geomorphological processes in the fluvial system result in accumulated deposit on the bed because the capacity to carry sediment has been exceeded. The bed load of the Aceh fluvial system is primarily generated by mechanical weathering resulting in boulders, pebbles, and sand, which roll or bounce along the river bed forming temporary deposits as bars on the insides of meander bends, as a result of a loss of transport energy in the system. This dynamic controls the style and range of deposits in the Aceh River. This study focuses on the spatial distribution of bed-load transport of the Aceh River. Understanding the spatial distribution of deposits facilitates the reconstruction of the changes in controlling factors during accumulation of deposits. One of the methods can be done by sieve analysis of sediment, where the method illuminates the distribution of sediment changes associated with channel morphology under different flow regimes. Hence, the purpose of this mini review is to investigate how the sediment along the river meander spatially dispersed. The results demonstrate that channel deposits in the Aceh River are formed from four different type of materials: pebble deposited along upstream left bank; sand located on the upstream, downstream, and along meander belts; and silt and clay located along the cut bank of meander bends. Because of different depositional pattern, the distribution of the sediment along the river can be used as a surrogate to identify bank stability, as well as to predict critical geometry for meander bend initiation

scholarly journals PENGARUH PERGERAKAN MEANDER TERHADAP KESEIMBANGAN ALUR SUNGAI

2019 ◽  
Vol 1 (2) ◽  
pp. 45
Author(s):  
Siti Murniningsih
Keyword(s):  
Sediment Load ◽  
Low Impact Development ◽  
Channel Cross Section ◽  
Fluvial System ◽  
Outer Banks ◽  
Meandering River ◽  
Sediment Loads ◽  
Meander Bends ◽  
Minimum Velocity ◽  
Sedimentation Processes

<span><em>Most of the river in Indonesia has a meander area especially located at the lower reach. Since the pattern of </em><span><em>the community behaviour in Indonesia, people live in surrounding or along the river while the river plains </em><span><em>and delta consist of alluvial soils, thus, meander migration usually occurs as a response to natural or manmade disturbances of the fluvial system. Meander River in urban area usually encourage sediment transport </em><span><em>problem such as riverbed aggradations at the area surrounding inside of the bank then will decrease the </em><span><em>river capacity in retaining flood while simultaneously eroding on the outer banks of meander bends. </em><span><em>Regarding velocity distribution at the channel cross section, the minimum velocity is occurring on the inside </em><span><em>of the meander, therefore some of the sediment loads is deposited. Related with the phenomena, protection </em><span><em>against sedimentation and erosion along meandering river extremely needed. Previously, river adjustment </em><span><em>within meander area are continually being made, therefore, eventually the gradient of a stream is altered to </em><span><em>accommodate the volume of water and the velocity necessary to transport the sediment load. In this paper,</em><span><em>understanding of various phenomenon’s in the meander area due to the sedimentation processes are </em><span><em>described and propose the new concept of protection with low impact development (LID) approach.</em></span></span></span></span></span></span></span></span></span></span></span><br /><br class="Apple-interchange-newline" /></span>

scholarly journals Use of Multidimensional Models to Investigate Boundary Shear Stress through Meandering River Channels

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3506
Author(s):  
Timothy J. Randle
Keyword(s):  
Shear Stress ◽  
Three Dimensional ◽  
Field Studies ◽  
River Channels ◽  
Meandering River ◽  
Boundary Shear ◽  
Wide Range ◽  
Channel Curvature ◽  
Boundary Shear Stress ◽  
Multidimensional Models

Three-dimensional hydraulics were simulated through a wide range of synthetically generated meandering river channels to determine how channel curvature and width would correlate with the maximum boundary shear stress. Multidimensional models were applied, similar to a computational flume to simulate a wide range of 72 meandering channels, developed from sine-generated curves. Cannel sinuosity ranged from 1.1 to 3.0 and included five consecutive meander bends. Longitudinal slopes of the various channels spanned four orders of magnitude, while bankfull discharges spanned three orders of magnitude. Using results from one-half of the simulation sets, an empirical correlation was found to predict the maximum boundary shear stress as a function of dimensionless ratios of channel curvature and width. The remaining simulation sets were used for verification. Multidimensional models were used to simulate channel hydraulics to efficiently investigate a wide range of channel sinuosity, width/depth ratios, bankfull discharges, and valley slopes. When simulating such a wide range of channel conditions, multidimensional models offer a more efficiency method of generating consistent datasets than either field studies or physical modeling. This paper demonstrates how multidimensional models can be used to identify important hydraulic relationships that are otherwise difficult to determine.

Simulation of Convective Flows in Sinusoidal Partitioned Enclosure

2009 ◽  
Author(s):  
S. H. Anilkumar ◽  
Biju T. Kuzhiveli
Keyword(s):  
Numerical Study ◽  
Valuable Insight ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Experimental Works ◽  
Isothermal Wall ◽  
Oriented Parallel ◽  
Rayleigh Numbers ◽  
Insight Into

A numerical study is carried out for natural convective flow and heat transfer in a two-dimensional enclosure with centrally located sinusoidal thin partition for a range of Rayleigh numbers, partition heights and aspect ratios. The partition is oriented parallel to the two vertical isothermal walls and the other surfaces are insulated. The flow and temperature distributions are taken to be two-dimensional. Transport equations are modeled by a stream function-vorticity formulation and are solved numerically by finite-difference approach. Comparisons with previously published numerical and experimental works are done and found to be in excellent agreement. The Rayleigh number varies from 103 to 106 and aspect ratio from 0.5 to 5. The results are presented for different fluids in the form of streamlines, vectors and isotherm plots. The variation of local Nusselt number over the sinusoidal partition and isothermal wall provide valuable insight into the physical processes.

Geometry and dynamics link form, function, and evolution of finch beaks

2021 ◽  
Vol 118 (46) ◽  
pp. e2105957118
Author(s):  
Salem al-Mosleh ◽  
Gary P. T. Choi ◽  
Arhat Abzhanov ◽  
L. Mahadevan
Keyword(s):  
Functional Form ◽  
Elementary Theory ◽  
Three Dimensional ◽  
Tissue Level ◽  
Cellular Level ◽  
Darwin's Finches ◽  
Aspect Ratios ◽  
Form Function ◽  
Darwin’S Finches ◽  
Curvature Driven

Darwin’s finches are a classic example of adaptive radiation, exemplified by their adaptive and functional beak morphologies. To quantify their form, we carry out a morphometric analysis of the three-dimensional beak shapes of all of Darwin’s finches and find that they can be fit by a transverse parabolic shape with a curvature that increases linearly from the base toward the tip of the beak. The morphological variation of beak orientation, aspect ratios, and curvatures allows us to quantify beak function in terms of the elementary theory of machines, consistent with the dietary variations across finches. Finally, to explain the origin of the evolutionary morphometry and the developmental morphogenesis of the finch beak, we propose an experimentally motivated growth law at the cellular level that simplifies to a variant of curvature-driven flow at the tissue level and captures the range of observed beak shapes in terms of a simple morphospace. Altogether, our study illuminates how a minimal combination of geometry and dynamics allows for functional form to develop and evolve.

scholarly journals Linear Error Dynamics for Turbulent Flow in Urban Street Canyons

2017 ◽  
Vol 56 (5) ◽  
pp. 1195-1208 ◽  
Author(s):  
K. Ngan ◽  
K. W. Lo
Keyword(s):  
Linear Theory ◽  
Free Atmosphere ◽  
Street Canyons ◽  
Urban Street ◽  
Eddy Simulation ◽  
Urban Street Canyons ◽  
Aspect Ratios ◽  
Large Eddy ◽  
Error Dynamics ◽  
Insight Into

AbstractThe ability to make forecasts depends on atmospheric predictability and the growth of errors. It has recently been shown that the predictability of urban boundary layers differs in important respects from that of the free atmosphere on the mesoscale and larger; in particular, nonlinearity may play a less prominent role in the error evolution. This paper investigates the applicability of linear theory to the error evolution in turbulent street-canyon flow. Using large-eddy simulation, streamwise aspect ratios between 0.15 and 1.50, and identical-twin experiments, it is shown that the growth rate of the error kinetic energy can be estimated from Eulerian averages and that linear theory provides insight into the spatial structure of the error field after saturation. The results should be applicable to cities with deep and closely spaced canyons. Implications for data assimilation and modeling are discussed.

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