Universiti Teknologi PETRONAS Civil Engineering Program in partial fulfillment of the requirement for Bachelor of Engineering (Hons). The geometric dimensions of the drainage system, vegetation properties and flow parameters such as flow depth, velocity and discharges will be measured for different flow scenarios in the drainage system. It is important to understand the hydraulics of flow over vegetation to manage the process.
In a half-channel with different densities, slope, flow velocity, height of natural vegetation and flow transition between vegetated and unvegetated belt in different flow regimes. All glory to the Almighty for His mercy in giving the author the strength and ability to complete the final year project. The author takes great pleasure in acknowledging all those individuals and organizations who helped make this book possible.
Firstly, the author would like to acknowledge her project leader, Assok Prof Hj Khamaruzaman B Wan Yusof for the valuable advice and supervision of the progress of the research. The author also wishes to dedicate this appreciation to Dr Izma and Dr Raza for their assistance and guidance and to a number of people for their cooperation in facilitating the learning process.
INTRODUCTION
- Background of Study
- Problem Statement
- Objectives of Project
- Scope of Project
- Relevancy of Project
The aquatic vegetation in open channel faces the problem of resistance formed by concentrated colonies of vegetation. However, the presence of vegetation in open channel flows is sometimes considered a problem because it can reduce flow capacity, with implications for flooding. The study of the impact of vegetation on water flow in an open channel has its particular importance.
Unrestrained growth of such vegetation in an open channel can lead to the complete loss of the hydraulic capacity that has the potential to generate floods. The presence of open channel vegetation is sometimes considered a problem because it can reduce flow capacity, with implications for flooding. Manning's equation will be used in modeling the hydraulic properties of flow through the vegetated open channel flow.
In this study, the influence of vegetation on the flow characteristics in an open channel is being experimentally investigated. The presence of aquatic vegetation in an open channel and in rivers significantly affects the velocity, depth of flow and magnitude of discharge.
LITERATURE REVIEW
Application of Aquatic Vegetation
Effects of Vegetation in Open-channel Flow
The proposed equations for modeling the vegetative coverage of the flow will be the basic equations developed for open channels according to Manning's equation as equation 1.1. Based on Equation 2, the author can conclude that the higher the density of the vegetation, the higher the value of Manning's roughness coefficient, n, and hence the lower the value of the flow rate, Q, because it is inversely proportional. The Manning roughness coefficient, n, represents the roughness of the friction exerted on the flow by the channel.
In many flow conditions, the choice of a Manning's roughness coefficient can have a large influence on calculation results. The results obtained from the laboratory experiment were then analyzed to obtain the Manning's roughness value, n. The Manning's roughness of vegetation shows the higher the density of vegetation, the value of Manning's roughness coefficient, n is higher; so the value of flow rate, Q will be lower as it is inversely proportional.
According to Manning's vegetation roughness below, the value of the flow rate depends on the value of n, which is the roughness coefficient. Results show that the value of Manning's roughness is higher in the vegetated zone compared to the non-vegetated zone. According to the calculated data, the author can conclude that the value of Manning's roughness is higher when there is varying roughness and alignment.
The highest value of Manning's roughness is for extremely poor alignment, deep pools, and vegetation or riverways with heavy timber and scrub. With the smallest value of this, Manning's roughness shows the very smooth and true surfaces without protrusions. Manning's roughness value increases with the increase in flow depth of vegetation in an open channel.
It is also found that increasing Manning's n value depends on increasing flow depth. The values of velocity and flow rate are inversely proportional to Manning's n. The Manning's vegetation roughness was calculated for different flow rates and vegetation densities. From the expected result, the author can conclude that the higher the density of vegetation, the value of Manning's roughness coefficient, n is higher; so the value of flow rate, Q will be lower as it is inversely proportional.
Experimental Conditions of Previous Studies
METHODOLOGY
- Study Methodology
- Experimental Methodology
- Materials
- Methods
- Gantt Chart FYP I
- Gantt Chart FYP II
Experimental approach will be used using a field open channel to investigate the hydrodynamics associated with natural vegetation instead of artificial vegetation. The present study will use an experimental approach using a field channel to investigate the hydrodynamics associated with natural vegetation, using the principles of open channel flow. Below is the proposed experimental approach where the experimental tests and measurements of the flow in an open channel were carried out using vegetation in a flood.
Characterization of the flow resistance (friction factors) due to the flexible roughness of the vegetation for different plant parameters was achieved. The depth gauge is an accurate measuring instrument, specially designed and used by engineers to measure flow depths. This scale is placed at the end of the open fairway to measure and calibrate the mass of water flowing through the aquatic plants.
The principle of operation is based on the proportionality between the velocity of the water and the resulting angular velocity of the meter rotor. Next, various runoff will be allowed to pass through the submerged vegetation where the upstream depth of water will be measured by depth gauge, similarly the depth of the downstream. The trial will begin by planting natural vegetation at the center of the rectangular embankment covering 1m length, which will be allowed to grow.
Also, in each run the inlet discharge as well as the outlet discharges will be determined using current meter with the rectangular current chute held horizontally. Crewing coefficient was highly correlated with vegetation density and inflow rate with empirical equations suggested. The Manning's equation is an empirical equation that applies to uniform flow in open channels and is a function of the channel velocity, flow area and channel slope.
The vegetation in gullies results in the loss of energy form and the slowing down of flowing water. According to Chen and Kao (2010), vegetated channels have recently been used to improve surface water quality and reduce sediment and nutrient inputs to rivers and open channels. Accurate discharge estimates, flow patterns and hydraulic characteristics in vegetated channels can be obtained by studying their velocity distribution.
RESULTS AND DISCUSSION
The water flow has a consistent value for any given point along the flume and few measurements have been made for comparison. Flow predictions in open channels generally assume that the flow is parallel and has a uniform velocity distribution (steady-uniform flow). As the speed varies, the author can conclude that with the available slope in the flume, the speed becomes faster, while the water depth decreases both upstream and downstream of the flume.
When analyzing flow through open channels of regular cross-sectional shape and hydraulic roughness, it is generally sufficient to use the total hydraulic radius as a parameter characterizing the cross-sectional properties. The results show that the depth of water flow in the vegetated area is much greater compared to the non-vegetated area. In this condition, the water surface is parallel to the bottom of the channel or S = Sw.
Channel slope can be expressed as an angle, percentage, or fraction. At a slope of 1:500, the flow depth value increases as the water flow flows through the vegetated area. From the graph below, it can be seen that the roughness value increases as the flow depth increases.
It was also found that the value of n increases with increasing flow depth. These results agree with the statement of Jarvel (2002) that the value of the roughness coefficient depends on the flow depth, where the Manning roughness coefficient increases while the frictional velocity decreases. The expected result will be able to determine the effect of vegetation on stream characteristics and may establish a relationship between Manning's vegetative roughness and stream depth.
It is expected that the determination of the velocity distribution at the end of this research will serve as an indicator for sediment deposition based on the degree of vegetation roughness. For the vegetated zone, the author decided to save 1 m length out of 10 m length of the flood. However, the results still show a positive value where it fully follows the concept of previous studies where the value of Manning's roughness should be higher where there is a varying roughness and alignment.
CONCLUSION AND RECOMMENDATION
The presence of vegetation in streams has numerous impacts by at least changing the magnitude and direction of the flow, which will affect the shape of the velocity profile, turbulence structures and sediment transport in an open channel flow. As the velocity of the channel increases, the aquatic vegetation slows down the flow at the bottom of the channel. Therefore, aquatic vegetation protects the bottom of the channel and reduces erosion. 2003), "Performance of A Sustainable Urban Drainage System in Malaysia", thesis of PhD from Universiti Sains Malaysia, Nibong Tebal, Seberang Prai Selatan.
Flow through Rigid Vegetation Hydrodynamics”, Master of Science Thesis, Virginia Polytechnic Institute and State University. Laboratory Experiments and Numerical Modeling of Wave Attenuation by Artificial Vegetation”, MSc, Ocean Engineering, Texas A&M University. 2009), “Laboratory Modeling of Open-Channel Flow Beyond Emerging Vegetation”, University of Manchester Master's Thesis.
