This document summarizes a study that used computational fluid dynamics (CFD) to simulate flow patterns around six types of triangular porous weirs with various upstream and downstream slopes. The study examined flow depth, discharge through the porous media, and velocity fields. Key findings include:
- Weirs with steeper upstream slopes produced lower upstream water levels and higher ratios of flow passing through the weir.
- The weir with a 30° downstream slope produced the highest upstream head and lowest discharge coefficient.
- Flow through the porous weirs reduced upstream water levels and vortex areas compared to solid weirs.
The Effect of Geometry Parameters and Flow Characteristics on Erosion and Sed...Dr. Amarjeet Singh
One of the most critical problems in the river
engineering field is scouring, sedimentation and morphology
of a river bed. In this paper, a finite volume method
FORTRAN code is provided and used. The code is able to
model the sedimentation. The flow and sediment were
modeled at the interception of the two channels. It is applied
an experimental model to evaluate the results. Regarding the
numerical model, the effects of geometry parameters such as
proportion of secondary channel to main channel width and
intersection angle and also hydraulic conditionals like
secondary to main channel discharge ratio and inlet flow
Froude number were studied on bed topographical and flow
pattern. The numerical results show that the maximum
height of bed increased to 32 percent as the discharge ratio
reaches to 51 percent, on average. It is observed that the
maximum height of sedimentation decreases by declining in
main channel to secondary channel Froude number ratio. On
the assessment of the channel width, velocity and final bed
height variations have changed by given trend, in all the
ratios. Also, increasing in the intersection angle accompanied
by decreasing in flow velocity variations along the channel.
The pattern of velocity and topographical bed variations are
also constant in any studied angles.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
The Effect of Geometry Parameters and Flow Characteristics on Erosion and Sed...Dr. Amarjeet Singh
One of the most critical problems in the river
engineering field is scouring, sedimentation and morphology
of a river bed. In this paper, a finite volume method
FORTRAN code is provided and used. The code is able to
model the sedimentation. The flow and sediment were
modeled at the interception of the two channels. It is applied
an experimental model to evaluate the results. Regarding the
numerical model, the effects of geometry parameters such as
proportion of secondary channel to main channel width and
intersection angle and also hydraulic conditionals like
secondary to main channel discharge ratio and inlet flow
Froude number were studied on bed topographical and flow
pattern. The numerical results show that the maximum
height of bed increased to 32 percent as the discharge ratio
reaches to 51 percent, on average. It is observed that the
maximum height of sedimentation decreases by declining in
main channel to secondary channel Froude number ratio. On
the assessment of the channel width, velocity and final bed
height variations have changed by given trend, in all the
ratios. Also, increasing in the intersection angle accompanied
by decreasing in flow velocity variations along the channel.
The pattern of velocity and topographical bed variations are
also constant in any studied angles.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and Development is an international premier peer reviewed open access engineering and technology journal promoting the discovery, innovation, advancement and dissemination of basic and transitional knowledge in engineering, technology and related disciplines.
We follow "Rigorous Publication" model - means that all articles appear on IJERD after full appraisal, effectiveness, legitimacy and reliability of research content. International Journal of Engineering Research and Development publishes papers online as well as provide hard copy of Journal to authors after publication of paper. It is intended to serve as a forum for researchers, practitioners and developers to exchange ideas and results for the advancement of Engineering & Technology.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Experimental flow visualization for flow around multiple side-by-side circula...Santosh Sivaramakrishnan
This paper deals with Flow visualization of multiple side by side circular cylinders of varying cross sections at Reynolds numbers from 50-200. An experimental setup for this purpose has been designed and described in the paper.
A Revisit To Forchheimer Equation Applied In Porous Media FlowIJRES Journal
A brief reference to various non-linear forms of relation between hydraulic gradient and velocity of
flow through porous media is presented, followed by the justification of the use of Forchheimer equation. In
order to study the nature of coefficients of this equation, an experimental programme was carried out under
steady state conditions, using a specially designed permeameter. Eight sizes of coarse material and three sizes
of glass spheres are used as media with water as the fluid medium. Equations for linear and non-linear
parameters of Forchheimer equation are proposed in terms of easily measurable media properties. These
equations are presented in the form of graphs as quick reckoners.
Large eddy simulation of the flow over a circular cylinder at high reynolds n...Jesús Martínez
The issue of numerical study of turbulent flow over a circular cylinder for different Reynolds numbers has been studied over almost 20 years. During those two decades, there have been successes and failures in the numerical models. This paper presents the implementation of the method of large eddy simulation (LES) to solve the problem of the external flow over a cylinder under a subcritical Reynolds number (Re = 1.4E +5). The purpose is to evaluate the performance of a computational method and complement experimental and numerical data presented in the literature, this as part of a research work which attempts to explain a method of passive drag reduction.
Effect of Height and Surface Roughness of a Broad Crested Weir on the Dischar...RafidAlboresha
Weir is usually incorporated as control or regulation devices in hydraulic systems,
with flow measurement as their secondary. It is normally intended for use in the field and thus
to regulate broad discharges. Broad-Crested weir is among the oldest common weir types. In this
paper, the effect of height and surface roughness for different Board Crested weirs models were
studied on discharge coefficient (Cd) in a horizontal open channel. In the crest of the weir,
certain materials may be combined with concrete (e.g., boulders) or may be used as cladding to
minimize the effect of water overflow (e.g. stone). The weir surface should not be considered
smooth in this case, and the discharge coefficient (Cd) must be re-estimated. For these purposes, laboratory flume was used to study the effect of height and surface roughness on the discharge coefficients with four of the different weir models dimensions of the concrete blocks. In this study, the flow conditions were considered to be free water flow and the viscosity effect was neglected. In all cases, the weir height effect was directly proportional to the discharge coefficient while the surface roughness effect was found to be inversely proportional to the coefficient Cd of the case study.
Topics:
1. Introduction to Fluid Dynamics
2. Surface and Body Forces
3. Equations of Motion
- Reynold’s Equation
- Navier-Stokes Equation
- Euler’s Equation
- Bernoulli’s Equation
- Bernoulli’s Equation for Real Fluid
4. Applications of Bernoulli’s Equation
5. The Momentum Equation
6. Application of Momentum Equations
- Force exerted by flowing fluid on pipe bend
- Force exerted by the nozzle on the water
7. Measurement of Flow Rate
a). Venturimeter
b). Orifice Meter
c). Pitot Tube
8. Measurement of Flow Rate in Open Channels
a) Notches
b) Weirs
Flow around multiple_inline_circular_cylindersAmey Vasulkar
The following paper deals with the visualization of flow around multiple inline circular cylinders. The conclusions from the visualizations are noted. Paper will serve has the base for further numerical investigations on the topic.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Multiphase flow is a phenomena of simultaneous flow of mixtures of phases such as gases (like bubbles) in a liquid, or liquid (like droplets) in gases and similar such flows. By multiphase flow we mean that its a mixture of phase and each phase in it has a distinct velocity field.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and TechnologyIJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Comparison of flow analysis of a sudden and gradual change of pipe diameter u...eSAT Journals
Abstract This paper describes an analytical approach to describe the areas where Pipes (used for flow of fluids) are mostly susceptible to damage and tries to visualize the flow behaviour in various geometric conditions of a pipe. Fluent software was used to plot the characteristics of the flow and gambit software was used to design the 2D model. Two phase Computational fluid dynamics calculations, using K-epsilon model were employed. This simulation gives the values of pressure and velocity contours at various sections of the pipe in which water as a media. A comparison was made with the sudden and gradual change of pipe diameter (i.e., expansion and contraction of the pipe). The numerical results were validated against experimental data from the literature and were found to be in good agreement. Index Terms: gambit, fluent software.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Experimental flow visualization for flow around multiple side-by-side circula...Santosh Sivaramakrishnan
This paper deals with Flow visualization of multiple side by side circular cylinders of varying cross sections at Reynolds numbers from 50-200. An experimental setup for this purpose has been designed and described in the paper.
A Revisit To Forchheimer Equation Applied In Porous Media FlowIJRES Journal
A brief reference to various non-linear forms of relation between hydraulic gradient and velocity of
flow through porous media is presented, followed by the justification of the use of Forchheimer equation. In
order to study the nature of coefficients of this equation, an experimental programme was carried out under
steady state conditions, using a specially designed permeameter. Eight sizes of coarse material and three sizes
of glass spheres are used as media with water as the fluid medium. Equations for linear and non-linear
parameters of Forchheimer equation are proposed in terms of easily measurable media properties. These
equations are presented in the form of graphs as quick reckoners.
Large eddy simulation of the flow over a circular cylinder at high reynolds n...Jesús Martínez
The issue of numerical study of turbulent flow over a circular cylinder for different Reynolds numbers has been studied over almost 20 years. During those two decades, there have been successes and failures in the numerical models. This paper presents the implementation of the method of large eddy simulation (LES) to solve the problem of the external flow over a cylinder under a subcritical Reynolds number (Re = 1.4E +5). The purpose is to evaluate the performance of a computational method and complement experimental and numerical data presented in the literature, this as part of a research work which attempts to explain a method of passive drag reduction.
Effect of Height and Surface Roughness of a Broad Crested Weir on the Dischar...RafidAlboresha
Weir is usually incorporated as control or regulation devices in hydraulic systems,
with flow measurement as their secondary. It is normally intended for use in the field and thus
to regulate broad discharges. Broad-Crested weir is among the oldest common weir types. In this
paper, the effect of height and surface roughness for different Board Crested weirs models were
studied on discharge coefficient (Cd) in a horizontal open channel. In the crest of the weir,
certain materials may be combined with concrete (e.g., boulders) or may be used as cladding to
minimize the effect of water overflow (e.g. stone). The weir surface should not be considered
smooth in this case, and the discharge coefficient (Cd) must be re-estimated. For these purposes, laboratory flume was used to study the effect of height and surface roughness on the discharge coefficients with four of the different weir models dimensions of the concrete blocks. In this study, the flow conditions were considered to be free water flow and the viscosity effect was neglected. In all cases, the weir height effect was directly proportional to the discharge coefficient while the surface roughness effect was found to be inversely proportional to the coefficient Cd of the case study.
Topics:
1. Introduction to Fluid Dynamics
2. Surface and Body Forces
3. Equations of Motion
- Reynold’s Equation
- Navier-Stokes Equation
- Euler’s Equation
- Bernoulli’s Equation
- Bernoulli’s Equation for Real Fluid
4. Applications of Bernoulli’s Equation
5. The Momentum Equation
6. Application of Momentum Equations
- Force exerted by flowing fluid on pipe bend
- Force exerted by the nozzle on the water
7. Measurement of Flow Rate
a). Venturimeter
b). Orifice Meter
c). Pitot Tube
8. Measurement of Flow Rate in Open Channels
a) Notches
b) Weirs
Flow around multiple_inline_circular_cylindersAmey Vasulkar
The following paper deals with the visualization of flow around multiple inline circular cylinders. The conclusions from the visualizations are noted. Paper will serve has the base for further numerical investigations on the topic.
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Multiphase flow is a phenomena of simultaneous flow of mixtures of phases such as gases (like bubbles) in a liquid, or liquid (like droplets) in gases and similar such flows. By multiphase flow we mean that its a mixture of phase and each phase in it has a distinct velocity field.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and TechnologyIJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Comparison of flow analysis of a sudden and gradual change of pipe diameter u...eSAT Journals
Abstract This paper describes an analytical approach to describe the areas where Pipes (used for flow of fluids) are mostly susceptible to damage and tries to visualize the flow behaviour in various geometric conditions of a pipe. Fluent software was used to plot the characteristics of the flow and gambit software was used to design the 2D model. Two phase Computational fluid dynamics calculations, using K-epsilon model were employed. This simulation gives the values of pressure and velocity contours at various sections of the pipe in which water as a media. A comparison was made with the sudden and gradual change of pipe diameter (i.e., expansion and contraction of the pipe). The numerical results were validated against experimental data from the literature and were found to be in good agreement. Index Terms: gambit, fluent software.
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Effect of free surface and froude number on the protection length and turbule...eSAT Journals
Abstract An experimental study was carried out to investigate the effect of free surface, Froude and Reynolds numbers on the protection length and turbulence through compound transitions using Laser Doppler, in a rectangular channel. Measurements of turbulence are carried out along the compound transition, at different contraction ratios, at different bed slopes. Vertical transition in the bed were also changed. From the results, the protection length increases with the increase of the incoming Froude number, and increases with the increase of the relative height, while it increases with the increase of the contraction ratio. The steep slope has a major effect on the protection length. Free surface has a unique role in governing the turbulence in open channel flows. Within and downstream of the transition, the turbulence occurs primarily in the wall region. Within the transition, flow tends towards the critical state (Fr approaches close to 1) with a rise in the turbulence intensities in the free surface and the wall region which may be attributed to the flow tending towards critical state. At small values of Froude number Fr ≤ 0.22, the effect of Froude number on turbulence intensities and the free surface waves negligible. Keywords: Turbulence intensities- Laser Doppler-Protection length-Free surface-Relative height-Contraction ratio-Bottom slope-Froude number
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Effect of inclined hump on the turbulence intensities and flow characteristic...eSAT Journals
Abstract In this paper, an experimental study was carried out to investigate the turbulence field and flow characteristics in the separated flow through inclined hump in water structures in rectangular channel using Laser. To study the variation of the turbulence, energy loss, relative energy (efficiency) and relative depth with main parameters affecting the inclined hump These parameters include the hump angle, relative height, upstream Froude number, bottom slope. Non-dimensional design curves are provided to relate the turbulence intensities and flow characteristics. The results show that, the variation of the energy loss increases till of hump angle about 45°. This rate of increase decreases about this value of angle of hump. The energy loss increases with the increasing of bed slope and relative height. The energy loss is quite high at a relative contraction of 0.3. Also, the results clearly showed the dependence of the hump inclination angle on the turbulence intensities. For hump angle ≥ 20°, the turbulence intensity in the separation zones was growing with increasing hump angles and the maximum was observed for hump inclination angles between 20° and 30°. The results indicated that, the most significant differences in flow structures occurred with hump angle less than 45°. Keywords: Energy loss-Turbulence intensities-Water structures- Hump-Laser Technique-Hump angle-Bottom slope-Relative height-Relative depth- Froude number-separation zones.
DSD-INT 2019 Fine sediments - transport in suspension, storage and supply - F...Deltares
Presentation by Prof. Dr. Mário J. Franca, IHE Delft & Delft University of Technology, The Netherlands, at the Delft3D - User Days (Day 3a: River morphodynamics), during Delft Software Days - Edition 2019. Wednesday, 13 November 2019, Delft.
Overbank Flow Condition in a River SectionIDES Editor
When the flows in natural or man made channel
sections exceed the main channel depth, the adjoining
floodplains become inundated and carry part of the river
discharge. Due to different hydraulic conditions prevailing in
the river and floodplain of a compound channel, the mean
velocity in the main channel and in the floodplain are different.
This leads to the transfer of momentum between the main
channel water and that of the floodplain making the flow
structure more complex. Results of some experiments
concerning the overbank flow distribution in a compound
channel are presented. Flow sharing in river channels is
strongly dependant on the interaction between flow in the
main channel and that in the floodplain. The influence of the
geometry on velocity and flow distribution and different
functional relationships are obtained. Dimensionless
parameters are used to form equations representing the over
bank flow sharing in the subsections. The equations agree
well with experimental discharge data and other published
data. Using the proposed method, the error between the
measured and calculated discharge distribution for the a
compound sections is found to be the minimum when compared
with that using other investigators.
LATTICE BOLTZMANN SIMULATION OF NON-NEWTONIAN FLUID FLOW IN A LID DRIVEN CAVITY IAEME Publication
Lattice Boltzmann Method (LBM) is used to simulate the lid driven cavity flow to explore the mechanism of non-Newtonian fluid flow. The power law model is used to represent the class of non-Newtonian fluids (shear-thinning and shear-thickening fluids) by considering a range of 0.8 to 1.6. Investigation is carried out to study the influence of power law index and Reynolds number on the variation of velocity profiles and streamlines plots. Velocity profiles and the streamline patterns
for various values of power law index at Reynolds numbers ranging 100 to 3200 are presented. Half way bounce back boundary conditions are employed in the numerical method.
lab 4 requermenrt.pdf
MECH202 – Fluid Mechanics – 2015 Lab 4
Fluid Friction Loss
Introduction
In this experiment you will investigate the relationship between head loss due to fluid friction and
velocity for flow of water through both smooth and rough pipes. To do this you will:
1) Express the mathematical relationship between head loss and flow velocity
2) Compare measured and calculated head losses
3) Estimate unknown pipe roughness
Background
When a fluid is flowing through a pipe, it experiences some resistance due to shear stresses, which
converts some of its energy into unwanted heat. Energy loss through friction is referred to as “head
loss due to friction” and is a function of the; pipe length, pipe diameter, mean flow velocity,
properties of the fluid and roughness of the pipe (the later only being a factor for turbulent flows),
but is independent of pressure under with which the water flows. Mathematically, for a turbulent
flow, this can be expressed as:
hL=f
L
D
V
2
2 g
(Eq.1)
where
hL = Head loss due to friction (m)
f = Friction factor
L = Length of pipe (m)
V = Average flow velocity (m/s)
g = Gravitational acceleration (m/s^2)
Friction head losses in straight pipes of different sizes can be investigated over a wide range of
Reynolds' numbers to cover the laminar, transitional, and turbulent flow regimes in smooth pipes. A
further test pipe is artificially roughened and, at the higher Reynolds' numbers, shows a clear
departure from typical smooth bore pipe characteristics.
Experiment 4: Fluid Friction Loss
The head loss and flow velocity can also be expressed as:
1) hL∝V −whe n flow islaminar
2) hL∝V
n
−whe n flow isturbulent
where hL is the head loss due to friction and V is the fluid velocity. These two types of flow are
seperated by a trasition phase where no definite relationship between hL and V exist. Graphs
of hL −V and log (hL) − log (V ) are shown in Figure 1,
Figure 1. Relationship between hL ( expressed by h) and V ( expressed by u ) ;
as well as log (hL) and log ( V )
Experiment 4: Fluid Friction Loss
Experimental Apparatus
In Figure 2, the fluid friction apparatus is shown on the right while the Hydraulic bench that
supplies the water to the fluid friction apparatus is shown on the left. The flow rate that the
hydraulic bench provides can be measured by measuring the time required to collect a known
volume.
Figure 2. Experimental Apparatus
Experimental Procedure
1) Prime the pipe network with water by running the system until no air appears to be discharging
from the fluid friction apparatus.
2) Open and close the appropriate valves to obtain water flow through the required test pipe, the four
lowest pipes of the fluid friction apparatus will be used for this experiment. From the bottom to the
top, these are; the rough pipe with large diameter and then smooth pipes with three successively
smaller diameters.
3) Measure head loss ...
1. Mohammad Tavakol- Sadrabadi- M.Sc. Student, Faculty of water Sciences Engineering, Shahid Chamran University of Ahvaz.
Prof .Manoochehr Fathi-moghaddam- Faculty of water Sciences Engineering, Shahid Chamran University of Ahvaz.
References
Introduction
.
through and overflow discharge:
velocity distribution and stream
lines:
Fig4. Relation between (
𝑸 𝒊𝒏
𝑸 𝒕𝒐𝒕𝒂𝒍
) and h/p
.
In upstream and close to solid weirs, the approach flow is separated in vertical plan and an adverse pressure gradient develops on front
face of the weir which makes an eddy in front of the solid weir. In the porous weir, a portion of upstream streamlines can pass through
the weir then pressure gradient is disappeared after weir.(Mohammadpour, Ghani et al. 2013)
Fig6. 2d velocity (left side) and stream wise velocity vectors (right side) around a&d) UsS30. b&e) UsS45. C&f) UsS60
Also results indicate that the flow inside porous domain is quite uniform and changes in velocity magnitude are small and negligible
mostly in weirs with downstream side slope.
In the present study, the flow pattern around rectangular porous weirs with various upstream and downstream slopes was simulated, using
a 3D numerical method. The VOF method and the (K-ε) Renormalized group (RNG) turbulence model was used to simulate fully three
dimensional flows. Results indicate that the DsS30° provides most upstream head and least to downstream. Also the ratio of through to
total flow discharge for constant h/p occurs in DsS30° is the lowest among investigated weirs and the reverse results occur in UsS60°.
The flow crosses through the weirs, weakens the vortex areas so more through discharge, causes smaller and weaker vortices around
weirs. Due to high through discharge, recirculation areas around DsS60° are completely disappeared. It should be noted that vortex areas
appeared only at downstream side of weirs with downstream side slope.
Governing Equations
Abstract
Gabion porous weirs are of environment friendly structures that are made from local materials and have least negative impact
on rivers. In this study a 3D-CFD code was utilized to simulate flow patterns about 6 types of Triangular porous weirs with
various upstream-downstream slopes in 6 discharges run the gamut from 3 to 30 liters per second. The porosity of all weirs was
constant and equal to 50% and also assumed to be made of spherical particles. Simulation results comprise flow surface profile;
velocity distribution around weirs, the ratio of through to overall flow discharge and vortex areas is presented. Results indicate
that the weir with upstream slope of 60° (UsS60°) provides least upstream water level and downstream speed and most ratio of
through to total flow for a constant discharge, and the reverse goes to the weir with downstream slope of 30° ( DsS30°).
Keywords: porous weir- CFD-velocity distribution- through flow discharge
A conventional weir typically consists of an impermeable body constructed of concrete, metal, rubber, etc., since its primary functions
are to collect water and efficiently regulate river flow. However, an impermeable body prevents the longitudinal movement of aquatic
life and transportation of physical and chemical substances in water, eventually having a negative impact on the river
environment.(Haneda 2005) The main characteristic of the materials used in ecological engineering methods is porosity. From the
viewpoint of water quality, physical and chemical substances such as sediments and suspended organic matter can pass downstream
through the permeable body. This eventually minimizes sedimentation and eutrophication in an impoundment. Between the stones,
bacteria inhabiting the granular surface may decompose organic matter. This biochemical reaction contributes to the purification of
river or canal water as it flows through the stones, just like in water purification and sewage water plants.(Mohamed 2010)
The objective of the present study is to investigate the effect of upstream and downstream slope of Triangular porous weirs on flow
depth, flow discharge in porous media and velocity fields in the vicinity of these weirs. Simulations were performed with a general-
purpose computational fluid dynamics (CFD) software, Flow-3D, which solves Reynolds’s average Navier- Stokes (RANS) equations.
The porosity of a porous medium is defined as the open volume divided by the total volume. By constructing a continuum model of the
porous material and applying averaging to each control volume, the usual conservation equations are obtained. Conservation of mass is
expressed as follows:
𝑉 𝑓
𝜕𝜌 𝑓
𝜕𝑡
+ ∇. 𝜌 𝑓
𝑈 = 0 (1)
This equation under assumption of incompressible flow can be expressed as:
𝜕𝑢
𝜕𝑥
+
𝜕𝑣
𝜕𝑦
+
𝜕𝑤
𝜕𝑧
= 0 (2)
Where U is the macroscopic flow velocity.
Momentum equations are as follows:
𝑢
𝜕𝑢
𝜕𝑥
+ 𝑣
𝜕𝑢
𝜕𝑦
+ 𝑤
𝜕𝑢
𝜕𝑧
= −
1
𝜌
𝜕𝑝
𝜕𝑥
+ 𝜗
𝜕2
𝑢
𝜕𝑥2 +
𝜕2
𝑢
𝜕𝑦2 +
𝜕2
𝑢
𝜕𝑧2 + 𝐺 𝑥 + 𝑓 𝑥
− 𝑏 𝑥 (3)
𝑢
𝜕𝑣
𝜕𝑥
+ 𝑣
𝜕𝑣
𝜕𝑦
+ 𝑤
𝜕𝑣
𝜕𝑧
= −
1
𝜌
𝜕𝑝
𝜕𝑦
+ 𝜗
𝜕2
𝑣
𝜕𝑥2 +
𝜕2
𝑣
𝜕𝑦2 +
𝜕2
𝑣
𝜕𝑧2 + 𝐺 𝑦 + 𝑓 𝑦
− 𝑏 𝑦 (4)
𝑢
𝜕𝑤
𝜕𝑥
+ 𝑣
𝜕𝑤
𝜕𝑦
+ 𝑤
𝜕𝑤
𝜕𝑧
= −
1
𝜌
𝜕𝑝
𝜕𝑧
+ 𝜗
𝜕2
𝑤
𝜕𝑥2 +
𝜕2
𝑤
𝜕𝑦2 +
𝜕2
𝑤
𝜕𝑧2 + 𝐺 𝑧 + 𝑓 𝑧
− 𝑏 𝑧 (5)
Where 𝜗 is the fluid kinematic viscosity; (u, v, w) are velocity components in three dimensions, ρ is the fluid density, (𝐺 𝑥,𝐺 𝑦,𝐺 𝑧) are
body accelerations, (fx, fy, fz) are viscous accelerations, (bx, by, bz) are flow losses in porous media.
Turbulence model:
The turbulence model used in this study is K-ε (RNG) method. The K-ε model is a sophisticated and widely used–model consists of two
transport equations for the turbulent kinetic energy 𝑘 𝑇 and its dissipation (𝜀 𝛵), the so-called k-ε model.(Harlow and Nakayama 1967)
Numerical modeling:
A steady state, incompressible and viscous flow was considered in this study with 6 discharges varying from 3 to 30 l/s. A first order
approximation of momentum equation and Power-Law scheme and the generalized minimum residual method (GMRES) was employed
to solve the computational domain. Fig.1 shows a sample of 3d mesh generation used to solve the computational domain.
Fig1-orthographic view of mesh quality and computational domain
6 types of weirs were investigated in total; 3 with upstream slope and 3 with downstream slopes of 30°, 45° and 60° with a constant
height of 16 cm. Porosity of all weirs is equal to 50% and is assumed to be formed of spherical particles of 32 mm diameter.
(K-ε) Renormalized group turbulence model was utilized to predict water surface profile and velocity distribution in the vicinity of
weirs.
Simulation Results and Analysis:
Water surface:
Water surface profile of flow over weirs with various upstream slopes in discharge of 3 l/s is presented in fig2. Based on simulation
results, the upstream head decreases by increasing in upstream/downstream slope. Also in all cases, the weirs with upstream slope
caused less upstream flow depth in comparison with the equal slope of downstream. The affiliation of upstream depth with minimum
downstream depth in all considered discharges for all investigated weirs is shown in fig 3.
Fig2. Water surface profile over porous weirs with various upstream/downstream slopes in discharge of 3 l/s
Results and Analysis
10th International River
Engineering Conference,19-21
Jan 2016, Ahvaz, Shahid
Chamran University.
Numerical Simulation of flow patterns around
Triangular porous weirs
irec10-03490305
0.00
0.05
0.10
0.15
0.20
0.25
0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
upstreamdepthofflow(m)
Downstream depth (m)
UsS 60° UsS 30° UsS 45°
DsS 60° DsS 30° DsS 45°
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4
Flowdepth(m)
Distance from weir's endpoint (m)
DsS 30 ° DsS 60 °
UsS 45° UsS60°
DsS45° UsS 30°
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
-0.1 0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5
Q(in)/Q(Total)
h/Lw
DsS 30 DsS 45
DsS 60 UsS 30
UsS 45 UsS 60
According to results, the weir with downstream slope of 30° (DsS30°)
produces maximum upstream head in all discharges. This means that
the (DsS30°) owns the least discharge coefficient (𝐶 𝑑).
The essence of flow about the gabion weirs is quite different from that of solid weirs. fraction of flow which crosses through the weir,
causes this discrepancy. This through discharge, results lower upstream level and its interaction with overflow causes more energy
dissipation. The definition of through and overflow discharges are of favorite topics for researchers. Fig 4. shows the dimensionless
graph of the ratio of through discharge to total discharge for various h/p conditions for each weir.
velocity distribution around porous weirs
with upstream and downstream slopes is
presented in fig.5. Simulation results
show that flow patterns and the velocity
vector around weirs are a function of
weir up/ downstream slope. Maximum
downstream X velocity at Q= 30 L/s
occurs on downstream slope of DsS30;
where the U component is about 1.5.
Also minimum U belongs to UsS 60;
which means this could be more effective
when the canal bed is susceptible to
erosion
Fig3. Relationship of Upstream-downstream
depth of flow over weirs in discharges of 3 to
30 l/s
Fig4. Relation between (
Qin
Qtotal
) and h/p
In the present study, recirculation areas around weirs are very
small to none because of high porosity ratio (50%) of
materials. To determine the probable circulations, a
comparison between 2d- velocity vectors and streamwise
velocity distribution around downsream slope weirs is
presented in fig 6. Based on simulation results, recirculation
flow, occurs at end of downstream slope of DsS30° and
DsS45°. The discharge crosses through the weirs, weakens the
vortex areas, so more through discharge causes less vorticity
and its shown in Fig7(c,f) where more through flow discharge
and velocity in DsS60 in comparison wih others, causes the
vortex to disappear.
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Fig5. Velocity distribution at upstream and downstream face of weirs with a) upstream slope and
Q=3l/s b) downstream slope Q= 3 l/s c) upstream slope at Q=30 l/s d) downstream slope at Q= 30
l/s
Conclusion