Spatially varied flow over rockfill embankments

1993 ◽  
Vol 20 (5) ◽  
pp. 820-827 ◽  
Author(s):  
J. A. Kells
Keyword(s):  
Physical Model ◽  
Flow Regime ◽  
Control Point ◽  
Flow Analysis ◽  
Free Surface Flow ◽  
Seepage Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
Seepage Analysis ◽  
The One

A procedure for determining the flow conditions through and over a simple, rockfill embankment having a horizontal top surface is presented. In this situation, the free surface flow regime can be characterized as spatially varied and the seepage flow regime as non-Darcian. Included in the paper are a review of spatially varied flow theory and analysis, a brief description of the numerical method used to conduct the non-Darcy seepage analysis, a few comments with respect to the determination of the flow properties of the model rockfill, and a discussion of the application of the analysis procedure to a model rockfill embankment. Two flow conditions were tested. The one flow condition was for partial overtopping of the embankment, while the other involved complete overtopping. The spatially varied flow analysis was carried out using a spreadsheet, and it included the incorportion of Hinds' method for control point location. A modified version of a Darcian finite element seepage program was used for the seepage analysis. The computed results are compared with those obtained from a physical model. As shown in the paper, the results are generally supportive of the proposed modeling procedure. Key words: control point, non-Darcy seepage, numerical model, physical model, porous media, rockfill, spatially varied flow.

Computational Study of the Downpull Force on High-Head Slide Gates

2019 ◽  
Author(s):  
Juan C. Arango Escobar ◽  
David Calderon Villegas ◽  
Aldo Benavides Moran ◽  
Alejandro Molina Ochoa
Keyword(s):  
Computational Study ◽  
Maximum Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Cfd Simulations ◽  
Ansys Fluent ◽  
Flow Through ◽  
High Head ◽  
The One ◽  
Bottom Outlet

Abstract This paper presents CFD simulations of the flow through a real bottom outlet equipped with high-head slide gates. The operating head of the gates and the maximum flow rate are 70 m and 650 m3/s, respectively. The numerical simulations were performed in ANSYS-FLUENT version 19.2. VOF method was used to model the free surface flow downstream the slide gates. Hydrodynamic forces were calculated at nine gate openings for a standard 45° lip gate; the downpull coefficients obtained from the simulations were compared with estimates from Naudascher’s analytical method. According to the CFD results, the downpull force acting on the 45° lip gate is 5%–10% lower than the one estimated analytically for the analyzed gate positions. Additionally, the flow through an inverted 30° lip gate was simulated to estimate the downpull coefficient at various gate openings. These coefficients cannot be determined analytically. The methodology here described can easily be applied to different gate geometries for which design coefficients are not available.

scholarly journals Boulder Pickup by Tsunami Surge

2019 ◽  
Vol 13 (05n06) ◽  
pp. 1941006
Author(s):  
Samuel Harry ◽  
Margaret Exton ◽  
Harry Yeh
Keyword(s):  
Pore Water Pressure ◽  
Initial Conditions ◽  
Scale Effects ◽  
Traditional Approach ◽  
Water Pressure ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Flow Conditions ◽  
The Difference ◽  
The Impact

Study of boulder transport by tsunamis is challenging because boulder size, shape, and composition vary greatly; furthermore, flow conditions, topography, and initial conditions are generally unknown. To investigate the mechanism of boulder pickup, experiments of tsunami-like flow past spherical boulders partially buried in a sediment bed are conducted. The experiments are performed in a large centrifuge facility to reduce scale effects and the corresponding dynamic similitude is discussed. The traditional approach to determine boulder pickup is adapted for the case of a half-buried spherical boulder. The adapted model predicts that the boulders are transported, but does not accurately predict the timing of pick up. To investigate the difference in pickup timing, two physical phenomena are discussed: pore-water-pressure dissipation in the soil, and the impact of the free-surface flow on hydrodynamic forces. For a spherical shaped boulder, vertical forces (i.e. buoyant and lift forces) are critical for the initiation of boulder pickup. It was found that spherical boulders that are three-quarter buried in the soil are not transported, even when exposed to flow conditions that would otherwise predict transport.

scholarly journals Outlet Flow Velocity in Circular Culvert

2014 ◽  
Vol 61 (3-4) ◽  
pp. 193-203
Author(s):  
Wojciech Szpakowski
Keyword(s):  
Free Surface ◽  
Flow Velocity ◽  
Flow Regime ◽  
Free Surface Flow ◽  
Bank Erosion ◽  
Surface Flow ◽  
Flowing Water ◽  
Channel Parameters ◽  
Outlet Flow ◽  
Bed Scour

AbstractThe outlet flow velocity in the end section of the culvert barrel depends in most cases on the culvert geometry, including the barrel slope, as well as on upstream and downstream channel parameters. Flowing water can create pressure flow or free surface flow in the culvert barrel. In the case of an unsubmerged barrel outlet, the free-surface flow is more frequent than the full flow. Increased velocities can cause channel bed scour and bank erosion downstream of the culvert outlet. Different culvert flow cases in which the barrel outlet is unsubmerged are presented in this paper. The influence of the flow regime on the outlet velocity is also discussed.

scholarly journals Experimental and Numerical Analysis for Earth-Fill Dam Seepage

2020 ◽  
Vol 12 (6) ◽  
pp. 2490 ◽  
Author(s):  
Ahmed Mohammed Sami Al-Janabi ◽  
Abdul Halim Ghazali ◽  
Yousry Mahmoud Ghazaw ◽  
Haitham Abdulmohsin Afan ◽  
Nadhir Al-Ansari ◽  
...  
Keyword(s):  
Physical Model ◽  
Numerical Models ◽  
Seepage Flow ◽  
Water Levels ◽  
The Body ◽  
Silty Sand ◽  
Internal Erosion ◽  
Dam Failure ◽  
Seepage Analysis ◽  
Earth Fill

Earth-fill dams are the most common types of dam and the most economical choice. However, they are more vulnerable to internal erosion and piping due to seepage problems that are the main causes of dam failure. In this study, the seepage through earth-fill dams was investigated using physical, mathematical, and numerical models. Results from the three methods revealed that both mathematical calculations using L. Casagrande solutions and the SEEP/W numerical model have a plotted seepage line compatible with the observed seepage line in the physical model. However, when the seepage flow intersected the downstream slope and when piping took place, the use of SEEP/W to calculate the flow rate became useless as it was unable to calculate the volume of water flow in pipes. This was revealed by the big difference in results between physical and numerical models in the first physical model, while the results were compatible in the second physical model when the seepage line stayed within the body of the dam and low compacted soil was adopted. Seepage analysis for seven different configurations of an earth-fill dam was conducted using the SEEP/W model at normal and maximum water levels to find the most appropriate configuration among them. The seven dam configurations consisted of four homogenous dams and three zoned dams. Seepage analysis revealed that if sufficient quantity of silty sand soil is available around the proposed dam location, a homogenous earth-fill dam with a medium drain length of 0.5 m thickness is the best design configuration. Otherwise, a zoned earth-fill dam with a central core and 1:0.5 Horizontal to Vertical ratio (H:V) is preferred.

Free Surface Flow Analysis by Smoothed Particle Hydrodynamics

2006 ◽  
Author(s):  
Jun Imasato ◽  
Yuzuru Sakai
Keyword(s):  
Free Surface ◽  
Smoothed Particle Hydrodynamics ◽  
Particle Density ◽  
Flow Analysis ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Pressure Poisson Equation ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Marker And Cell Method

In this study a new computational algorithm to enforce incompressibility in free surface flow analysis using Smoothed Particle Hydrodynamics (SPH) is presented. The method uses two steps. The first step is a fractional step for solving velocity field forward in time without incompressibility. Then the second step is computed to compensate the pressure Poisson equation using the mass constant equation in a particle field. This method is composed of the above two steps and is similar to SMAC (Simplified Marker and Cell) method commonly used in CFD. However in SPH simulation, the introduction of incompressibility of fluid is easily realized using the particle density concept and the boundary of free surface of fluid is also controlled conveniently by the concept. In this study the algorithm is applied to sloshing problems of vessels with fluid. The numerical results using this algorithm show good results in the behaviors of free surface flow and the pressure evaluations at the wall of the vessels.

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