Sandbars in alluvial channels: their formation processes and interaction with groins

2014 ◽  
Vol 11 (5) ◽  
pp. 473-480
Author(s):  
M. Alauddin ◽  
T. Tsujimoto
Keyword(s):  
Initial Conditions ◽  
Periodic Boundary Conditions ◽  
Main Channel ◽  
Low Flow ◽  
Formation Processes ◽  
River Engineering ◽  
Alluvial Channels ◽  
Dimensional Model ◽  
Inland Waterways ◽  
Lowland Rivers

Large sandbars resulted from the instability of loose sedimentary materials are very common in lowland rivers. These, not only, interrupt the inland waterways at low flow, but also make the channels highly unstable forming anabranches, influencing bank erosion, and so on. Groins have key roles to play in such cases. Formation processes of sandbars and their interactions with groins become very urgent to learn for better management of river engineering. RIC-Nays, a two-dimensional model for flow and morphology, is utilized in this study. Computation results reveal that different initial conditions lead to different equilibrium states, and periodic boundary conditions with a small computation domain tend to stabilize multiple bars. Intrusion of groins accelerates the flow in the main channel, which triggers the sediment movement there. Thus the bars move downstream reducing their scale and finally they disappear from the main channel.

Orientation of groins for wide and dynamic lowland rivers

2014 ◽  
Vol 11 (4) ◽  
pp. 431-440
Author(s):  
M. Alauddin ◽  
T. Tsujimoto
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Bank Erosion ◽  
Main Channel ◽  
High Flow ◽  
Local Scour ◽  
Low Flow ◽  
Alluvial Rivers ◽  
Lowland Rivers ◽  
2D Numerical Model

Alluvial rivers at lowland are very complex in nature. Severe bank erosion at high flow and undue sedimentation at low flow are very common there. Groins are not functioning successfully with their present arrangements. This study investigates various orientations of groins to identify the optimum one for the effective functioning at high flow and low flow both. A 2D numerical model, RIC-Nays is utilized upon confirmation through detailed experimental data. Two types of groins: non-permeable and permeable, and four orientations: 100°, 90°, 80° and 70° to the bank line downstream are considered. Computation reveals that smaller angled groins function better through deepening the main channel and minimizing the local scour, except deposition near bank reduces.

scholarly journals EXACT SOLUTION OF AN IRREVERSIBLE ONE-DIMENSIONAL MODEL WITH FULLY BIASED SPIN EXCHANGES

1996 ◽  
Vol 10 (25) ◽  
pp. 3451-3459 ◽  
Author(s):  
ANTÓNIO M.R. CADILHE ◽  
VLADIMIR PRIVMAN
Keyword(s):  
Exact Solution ◽  
Domain Wall ◽  
Nearest Neighbor ◽  
Spin Exchange ◽  
Initial Conditions ◽  
Strong Dependence ◽  
Zero Temperature ◽  
Dimensional Model ◽  
One Dimensional ◽  
Temperature Dynamics

We introduce a model with conserved dynamics, where nearest neighbor pairs of spins ↑↓ (↓↑) can exchange to assume the configuration ↓↑ (↑↓), with rate β(α), through energy decreasing moves only. We report exact solution for the case when one of the rates, α or β, is zero. The irreversibility of such zero-temperature dynamics results in strong dependence on the initial conditions. Domain wall arguments suggest that for more general, finite-temperature models with steady states the dynamical critical exponent for the anisotropic spin exchange is different from the isotropic value.

Sensitivity analysis of non-point sources in a water quality model applied to a dammed low-flow-reach river

2008 ◽  
Vol 57 (8) ◽  
pp. 1295-1300
Author(s):  
Nayana G. M. Silva ◽  
Marcos von Sperling
Keyword(s):  
Water Quality ◽  
Sensitivity Analysis ◽  
Initial Conditions ◽  
Quality Parameters ◽  
Water Quality Model ◽  
Point Sources ◽  
Low Flow ◽  
Treated Wastewater ◽  
Quality Model ◽  
River Bed

Downstream of Capim Branco I hydroelectric dam (Minas Gerais state, Brazil), there is the need of keeping a minimum flow of 7 m3/s. This low flow reach (LFR) has a length of 9 km. In order to raise the water level in the low flow reach, the construction of intermediate dikes along the river bed was decided. The LFR has a tributary that receives the discharge of treated wastewater. As part of this study, water quality of the low-flow reach was modelled, in order to gain insight into its possible behaviour under different scenarios (without and with intermediate dikes). QUAL2E equations were implemented in FORTRAN code. The model takes into account point-source pollution and diffuse pollution. Uncertainty analysis was performed, presenting probabilistic results and allowing identification of the more important coefficients in the LFR water-quality model. The simulated results indicate, in general, very good conditions for most of the water quality parameters The variables of more influence found in the sensitivity analysis were the conversion coefficients (without and with dikes), the initial conditions in the reach (without dikes), the non-point incremental contributions (without dikes) and the hydraulic characteristics of the reach (with dikes).

scholarly journals Global Attractors of Sixth Order PDEs Describing the Faceting of Growing Surfaces

2015 ◽  
Vol 28 (1) ◽  
pp. 49-67 ◽  
Author(s):  
M. D. Korzec ◽  
P. Nayar ◽  
P. Rybka
Keyword(s):  
Boundary Conditions ◽  
Periodic Boundary ◽  
Initial Conditions ◽  
Periodic Boundary Conditions ◽  
Global Attractors ◽  
Sixth Order ◽  
Two Dimensional ◽  
One Dimensional ◽  
Crystalline Surface ◽  
Dimensional Version

Abstract A spatially two-dimensional sixth order PDE describing the evolution of a growing crystalline surface h(x, y, t) that undergoes faceting is considered with periodic boundary conditions, as well as its reduced one-dimensional version. These equations are expressed in terms of the slopes $$u_1=h_{x}$$ u 1 = h x and $$u_2=h_y$$ u 2 = h y to establish the existence of global, connected attractors for both equations. Since unique solutions are guaranteed for initial conditions in $$\dot{H}^2_{per}$$ H ˙ p e r 2 , we consider the solution operator $$S(t): \dot{H}^2_{per} \rightarrow \dot{H}^2_{per}$$ S ( t ) : H ˙ p e r 2 → H ˙ p e r 2 , to gain our results. We prove the necessary continuity, dissipation and compactness properties.

High Pressure Diesel Engine Modeling

2003 ◽  
Author(s):  
Riccardo Baudille ◽  
Gino Bella ◽  
Rossella Rotondi
Keyword(s):  
Liquid Fuel ◽  
Initial Conditions ◽  
Injection Velocity ◽  
Dimensional Model ◽  
Flow Conditions ◽  
One Dimensional ◽  
Engine Modeling ◽  
Fuel Jet ◽  
Initial Drop ◽  
The One

In multi hole Diesel injectors, cavitation can offer advantages in the development on the fuel spray, because the primary atomization of the liquid fuel jet can be improved due to the enhanced turbulence. Several multi dimensional models of cavitating nozzle flow have been developed in order to provide information about the flow at the exit of a cavitating orifice. In this paper an analytical one-dimensional model, by Sarre et al. [1], to predict the flow conditions at the exit of a cavitating nozzle, is analyzed. The results obtained are compared with the ones obtained using the multi dimensional code Fluent in order to investigate the predictive capability of the one-dimensional code. The model provides initial conditions for multidimensional spray modeling: the effective injection velocity and the initial drop or injected liquid ‘blob’ size. The simulations were performed using an improved version of the KIVA3V code, in which an hybrid break up model, developed by the authors, is used and the results in terms of penetrations and global SMD are compared with the experimental ones. The one dimensional model predicts reasonable discharge coefficient for sharp injector geometry. Where the r/d ratio increases and the cavitation effects appear not clearly marked there are same discrepancies between the one dimensional and the multidimensional approach.

Dissipative Solitons and Metastable States in a Chain of Active Particles

2018 ◽  
Vol 28 (08) ◽  
pp. 1830027 ◽  
Author(s):  
Alexandr P. Chetverikov ◽  
Konstantin S. Sergeev ◽  
Ezequiel del Rio
Keyword(s):  
Morse Potential ◽  
Initial Conditions ◽  
Periodic Boundary Conditions ◽  
Nonuniform Distribution ◽  
Metastable States ◽  
Active Particles ◽  
Dissipative Solitons ◽  
Random Initial Conditions ◽  
A Chain ◽  
Excitation Probability

The dynamics of a chain of interacting active particles of Rayleigh-type is studied. Particles are interconnected via Morse potential forces. The steady-state modes (attractors) of the chain with periodic boundary conditions look like cnoidal waves with a uniform distribution of the particles’ density maxima along the chain. However, if the system starts from random initial conditions, a metastable state with nonuniform distribution of density maxima is formed. Characteristics of metastable states, excitation probability of different modes and their lifetimes are studied by numerical simulation.

One-Dimensional Nonlinear Parametric Instability of Inhomogeneous Plasma: Time Domain Problem

2021 ◽  
Vol 24 (3) ◽  
pp. 272-279
Author(s):  
N. V. Gerasimenko ◽  
F. M. Trukhachev ◽  
E. Z. Gusakov ◽  
L. V. Simonchik ◽  
A. V. Tomov
Keyword(s):  
Initial Conditions ◽  
Inhomogeneous Plasma ◽  
Parametric Instability ◽  
Analytical Models ◽  
Dimensional Model ◽  
One Dimensional ◽  
Proposed Model ◽  
Wide Range ◽  
Spatial And Temporal Characteristics ◽  
Good Agreement

A numerical one-dimensional model of convective parametric instability of inhomogeneous plasma is developed. By using this model, a numerical solution describing spatial and temporal characteristics of interacting waves is obtained. The results obtained are in a good agreement with known analytical models and substantially generalize them. In particular, an important advantage of the proposed model is the possibility of varying initial conditions, analyzing behavior of the system in the presence of incident wave fluctuations that is important for the future study of the absolute instability mode. The model is also provides possibility to simulate absolute parametric instability with a wide range of controllable parameters, as well as to study interacting wave transients.

Justification of Non-Dimensional Schemes and Identification of Parameters on Modelling Electrokinetic Transport Phenomena in Microchannels

2010 ◽  
Author(s):  
Zhanjie Shao ◽  
Gerry Schneider ◽  
Carolyn Ren
Keyword(s):  
Initial Conditions ◽  
Transport Phenomena ◽  
Concentration Field ◽  
Electrokinetic Transport ◽  
Dimensional Model ◽  
Applied Potential ◽  
Governing Equations ◽  
Numerical Studies ◽  
Electrokinetic Flows ◽  
On Chip

The electrokinetic transport phenomena are to be numerically studied based on cross-linked microchannel networks, which have been commonly employed for on-chip capillary electrophoresis applications. Applied potential field, flow field and concentration field should be solved to predict the species transport process under electrokinetic flows. Together with the well-designed channel geometry, a detailed physical model was firstly formulated through a series of governing equations and corresponding boundary/initial conditions, which was briefly re-presented from our previous publications. The emphasis of current work was to justify the simplest non-dimensional scheme and identify the most beneficial parameters so that an effective and simplified non-dimensional model was developed for numerical studies.

Experiments on Tube/Support Interaction With Feedback-Controlled Instability

1992 ◽  
Vol 114 (1) ◽  
pp. 23-32 ◽  
Author(s):  
J. Antunes ◽  
F. Axisa ◽  
M. A. Vento
Keyword(s):  
Heat Exchanger ◽  
Initial Conditions ◽  
Low Flow ◽  
Test Model ◽  
Actual Behavior ◽  
Heat Exchanger Tube ◽  
System Parameters ◽  
Tube Bundles ◽  
Fluidelastic Instability ◽  
Exchanger Tube

Due to tube-support gaps in heat-exchangers, low-frequency modes may develop and become unstable at comparatively low flow velocities. This kind of linear fluidelastic instability results in a negative modal damping value, which is a function of the flow velocity. The response amplitude of the unstable tubes increases steadily until tube-support impact becomes unavoidable. These extremely nonlinear vibratory motions have a high-risk potential, as tube velocities and impact forces can be of very considerable magnitude. This paper reports results on a series of laboratory experiments, intended to validate nonlinear calculations on vibro-impact dynamics of heat exchanger tube bundles under fluidelastic instability. The test model was designed for unidirectional motion and the results obtained should be fairly representative of the actual behavior of the U-bend portion of the heat exchanger tube bundles. The system instability is generated by a velocity feedback loop. This method presents significant advantages due to simplicity of the setup and the controllability of the system parameters, in particular concerning the negative damping ratio of the unstable model. A comparison of experimental and computed system dynamics is presented for several values of the instability growth rate and for various initial conditions of the motion. Influence of other parameters, such as tube-support gap magnitude and gap symmetry, is asserted for realistically ranged values. Results show that several steady motion regimes may arises, depending on the system parameters and initial conditions of the motion, which is a fact of engineering significance. Furthermore, a satisfactory qualitative and quantitative agreement was obtained between theoretical predictions and test data.

Sign in / Sign up

Export Citation Format

Share Document