CIVIL ENGINEERING SOFTWARE (BFC 43201) PDF

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UNIVERSITI TUN HUSSEIN ONN MALAYSIAASSINGNMENT 1SEMESTER ISESSION 2021/COURSE NAME : HEC-RAS SOFTWARECOURSE CODE : BFC 43201 (S7)NAME : KEANE ALDRIGE ANAK LAWINLECTURER : Ts DR SABARIAH MUSADATE : 15 DECEMBER 2021EVALUATION : MARK TOTAL10- CHANNEL DESIGN -CIVIL ENGINEERING SOFTWARE (BFC 43201)SEMEST...

Description

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

ASSINGNMENT 1 SEMESTER I SESSION 2021/2022 COURSE NAME

:

HEC-RAS SOFTWARE

COURSE CODE

:

BFC 43201 (S7)

NAME

:

KEANE ALDRIGE ANAK LAWIN

LECTURER

:

Ts DR SABARIAH MUSA

DATE

:

15 DECEMBER 2021

EVALUATION

:

MARK

TOTAL

10

- CHANNEL DESIGN -

CIVIL ENGINEERING SOFTWARE (BFC 43201) SEMESTER 1 SESSION 2021/2022 ASSIGNMENT 1 - INDIVIDUAL

ANSWER ALL QUESTIONS 1.

Explain clearly, four main application of HECRAS in Hydraulic Engineering

User Interface A graphical user interface allows the user to communicate with HEC-RAS (GUI). The major goal of the interface design was to make the programme simple to use while retaining a high degree of efficiency for the user. The following functions are available through the interface: -

File Management

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Data Entry and Editing

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Hydraulic Analyses

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Tabulation and Graphical Displays of Input and Output Data

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Inundation mapping and animations of water propagation

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Reporting Facilities

-

Context Sensitive Help Hydraulic Analysis Components Several river analysis components are included in the HEC-RAS system, including: (1) steady flow water surface profile computations; (2) one- and two-dimensional unsteady flow simulations; (3) moveable boundary sediment transport calculations; and (4) water quality analysis. The usage of a single geometric data structure and shared geometric and hydraulic computing methods by all four components is a crucial feature. The system also includes various hydraulic design aspects that may be used once the fundamental water surface profiles have been calculated.

Steady Flow Water Surface Profiles This part of the modelling system calculates water surface profiles for a constant but progressively changing flow. A whole network of channels, a dendritic system, or a single river reach may all be handled by the system. The steady flow component can describe water surface profiles in subcritical, supercritical, and mixed flow regimes.

The solution of the one-dimensional energy equation is the foundation of the computational technique. Friction (Manning's equation) and contraction/expansion are used to calculate energy losses (coefficient multiplied by the change in velocity head). In instances where the water surface profile is quickly changing, the momentum equation might be applied. Mixed flow regime calculations (hydraulic leaps), bridge hydraulics, and assessing profiles at river confluences are examples of these circumstances (stream junctions).

One- and Two-Dimensional Unsteady Flow Simulation This component of the HEC-RAS modelling system can simulate unsteady flow in one dimension, two dimensions, and a combination of one and two dimensions over a network of open channels, floodplains, and alluvial fans. In the unsteady flow computations module, the unsteady flow component may be utilised to conduct subcritical, supercritical, and mixed flow regime (subcritical, supercritical, hydraulic leaps, and drawdowns) calculations. The steady flow component's hydraulic computations for cross-sections, bridges, culverts, and other hydraulic structures were merged into the unstable flow module. The unstable flow component has a number of unique features, including significant hydraulic structural capabilities. Pumping stations; navigation dam operations; pressured pipe systems; automatic calibration features; User set rules; and integrated one and two-dimensional unsteady flow modelling

Steady Transport/Movable Boundary Computations

This part of the modelling system is used to simulate one-dimensional sediment movement and moveable boundary calculations caused by scour and deposition over long periods of time (typically years, although applications to single flood events are possible). The sediment transport potential is calculated by grain size fraction, allowing hydraulic sorting and armoring to be simulated. The capacity to model a comprehensive network of streams, channel dredging, multiple levee and encroachment options, and the use of many distinct equations for sediment transport calculation are all notable features.

The model is intended to mimic long-term scour and deposition patterns in a stream channel as a result of changing the frequency and duration of water discharge and stage, as well as changing the channel shape. This approach may be used to estimate maximum feasible scour during significant flood events, design channel contractions necessary to maintain navigation depths, anticipate the effect of dredging on the rate of deposition, and analyse sedimentation in permanent channels.

Water Quality Analysis The user can do riverine water quality evaluations with this component of the modelling system. This version of HEC–RAS includes an advection-dispersion module, which allows you to model water temperature. This new module solves the onedimensional advection-dispersion equation utilising a control volume technique with a fully integrated heat energy budget using the QUICKEST-ULTIMATE explicit numerical scheme. HEC-RAS now includes transport and fate of a restricted set of water quality elements. Dissolved Nitrogen (NO3-N, NO2-N, NH4-N, and Org-N); Dissolved Phosphorus (PO4-P and Org-P); Algae; Dissolved Oxygen (DO); and Carbonaceous Biological Oxygen Demand are the currently accessible water quality elements (CBOD).

RAS Mapper HEC-RAS can conduct inundation mapping of water surface profile findings straight from the HEC-RAS software. The RAS Mapper creates inundation depth and floodplain boundary information using the HEC-RAS geometry and calculated water surface profiles. For examination of velocity, shear stress, stream power, ice thickness, and floodway encroachment data, additional geographical data can be created. You'll need a terrain model in binary raster floating-point format to utilise the RAS Mapper for analysis (.flt). The resulting depth grid is saved as a.flt file, while the boundary dataset is saved as a Shapefile file for use with GIS tools.

Graphics and Reporting X-Y plots of the river system schematic, cross-sections, profiles, rating curves, hydrographs, and inundation mapping are all included in the graphics. There's also a three-dimensional visualisation of numerous cross-sections. In the HEC-RAS Mapper

section of the programme, inundation mapping is done. Flood maps can be dynamic and include numerous backdrop layers (terrain, aerial photos, etc.). There is a tabular output option. Users can choose from pre-made tables or create their own bespoke ones. All graphical and tabular output may be displayed on the screen, transmitted straight to a printer (or plotter), or copied to a word processor or spreadsheet via the Windows Clipboard.

Data Storage and Management The usage of "flat" files (ASCII and binary), the HEC-DSS (Data Storage System), and HDF5 are all used to store data (Hierarchical Data Format, Version 5). User input data is saved in flat files organised by project, plan, geometry, steady flow, unsteady flow, quasi-steady flow, sediment data, and water quality data. The majority of the output data is saved in separate binary files (HEC and HDF5). Using the HEC-DSS, data may be transmitted between HEC-RAS and other applications. The user interface is used to handle the information. For the project being produced, the modeller is asked to input a single filename. All additional files are automatically generated and named as needed by the interface after the project filename is supplied. On a project-by-project basis, the interface allows for file renaming, relocation, and deletion.

(12 marks) 2.

Discuss critical depth determination. (8 marks)

The critical depth is a number that is crucial to comprehending the flow characteristics. The flow is deemed "subcritical" if the actual depth is more than the critical depth. The term "subcritical flow" refers to "slow flow" that is influenced by downstream circumstances. Subcritical -

When the actual water depth is larger than the critical depth, subcritical occurs. Gravitational forces dominate subcritical flow, which acts slowly and consistently. It's characterised as having a Froude number of one or fewer.

Supercritical

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Inertial forces control supercritical flow, which acts as a fast or unstable flow. A hydraulic leap occurs when supercritical flow changes to subcritical, resulting in a large energy loss and erosive potential. It is defined as supercritical when the actual depth is less than the critical depth. The Froude number of supercritical flow is more than one.

Critical -

The transition or control flow with the least amount of energy for that flow rate is called critical flow. The Froude number for critical flow is one. When the Froude number equals one, the flow depth is one. The flow depth at which a particular discharge is maximal for a given specific energy, or the flow depth at which a given discharge occurs with the least amount of specific energy.

3.

Discuss energy, mass and momentum equation. Energy - In fluid mechanics, energy is expressed as velocity, pressure, and datum (Height). Despite the fact that they are distinct types of energy, they are measured in the same way. Bernoulli's theorem, which claims that these energies are conserved, is named after him.

-Energy in the form of Velocity is called Velocity head. -Energy in the form of Pressure is called Pressure head. -Energy in the form of Datum is called Potential head.

Mass -

The mass of any thing is equal to the volume of the object multiplied by its density. The density, volume, and form of a fluid (a liquid or a gas) can all change over time inside the domain.

Momentum equation -

The momentum equation is used in open channel flow problems to determine unknown forces (F) acting on the walls or bed in a control volume. In comparison to the energy equation that deals with scalar quantities such as mass (m), pressure (P), and velocity magnitude (V), the momentum equation deals with vector quantities such as velocity vector and forces (F). Therefore it is critical to write a momentum equation in a known direction and use the component of the forces within the defined direction. Using Newton’s second law of motion, which equates the rate of change of momentum (M=mV ) with the algebraic sum of all external forces, the momentum equation can be written as:

Further, the rate of change of momentum can be divided into two terms as:

(12 marks)

4.

An engineer is to analyze flow in an open channel. The channel is designed to be constricted by placing bridge embankment at both sides of the channel. Explain the consequences due to the constriction.

If there is no loss due to constriction, the specific energy at the constriction will be the same as upstream of it, and because the width of the constriction is reduced, the depth of the flow will increase to maintain the specific energy constant. Another consequence could be that if the reduced width is less than the minimum width to allow flow, the energy at the upstream will work as critical energy for the constriction section, and flow Depth can increase or decrease.

(8 marks) 5.

A spillway discharges a flood flow at a rate of q = 7.75 m3/s per meter width. At the downstream horizontal apron the depth of flow was found to be 0.50 m. What tail water depth, y2 is needed to form a hydraulic jump? If a jump is formed, find its (i) Type of jump, (ii) Energy loss, (iii) Percentage of energy loss to the initial energy (iv) Power dissipated per meter width of the channel (10 marks)...