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Courses

CENV6164 River Engineering

Module Overview

River beds are often made of granular material that can be displaced by the water flow from one location to another, thus establishing areas of erosion and accumulation. Quantitative prediction of sediment erosion and accumulation rates is crucial for many applications in Civil and Environmental Engineering including, dam silting and bridge scouring to name just a few. Furthermore, fluvial sediment transport can result in the formation of large bed-forms (e.g. ripples, dunes, bars), which need to be accounted for to quantify flow resistance and hence to design river embankments to contain flood events. This module covers aspects of fluid and sediment dynamics that will allow you to critically assess the stability of a river bed and to address sediment mass balance as a function of flow characteristics. Teaching and learning activities include traditional lectures, seminars by external people and group discussion of relevant research papers. Pre-requisite module/s: CENV2008 Hydraulics

Aims and Objectives

Module Aims

• The general aim of this module is to introduce students to the theory of fluvial sediment transport and its application to solve relevant problems in hydraulic engineering. Studying sediment transport implies having a thorough knowledge of flow processes in rivers. For this reason the course is divided into two parts: part 1 covers aspects of open channel hydrodynamics, which are then used to address the topics of sediment transport theory and practice introduced in part 2.Covering all aspects of fluvial sediment transport that are relevant to hydraulic engineering is a task that goes well beyond the scope of this module. However, the emphasis here is to provide students with a set of “thinking tools” and an approach to studying that will allow them to address successfully any problem they may encounter as riverengineers.

Learning Outcomes

Knowledge and Understanding

Having successfully completed this module, you will be able to demonstrate knowledge and understanding of:

  • Incipient motion of sediment grains and channel stability
  • Sediment transport modelling approaches
  • Governing equations of turbulent open channel flows (Navier Stokes and Reynolds equations)
  • Sediment characterization
  • Sediment transport mechanics
Transferable and Generic Skills

Having successfully completed this module you will be able to:

  • Problem analysis and problem solving
  • Group work/team work
  • Report writing
  • Discussion of research papers
Subject Specific Practical Skills

Having successfully completed this module you will be able to:

  • Determine river bed/banks stability
  • Carry out and present engineering calculations
  • Identify different modes of sediment transport
  • Quantify bed-form and grain roughness effects on flow resistance
  • Choose the appropriate formula to estimate sediment transport rates in rivers and channels
  • Critically assess local and general scour around bridge foundations
  • Quantify general and local scour around bridge piers and abutments.
  • Critically assess the uncertainty of empirical methods used to address various sediment transport problems
  • Use Hec Ras for sediment transport assessment in rivers.
  • Exercise technical judgement and make decisions
Subject Specific Intellectual and Research Skills

Having successfully completed this module you will be able to:

  • Critically analyse local and integral equations governing momentum and mass balance in open channel flows. Appreciate the nature of shear stress in open channel flows.
  • Derive mean velocity profiles in turbulent open channel flows and appreciate their importance in determining sediment transport rates in rivers.
  • Identify the coupling between turbulence and sediment dynamics in fluvial environments.
  • Derive sediment-mass balance equations and use them to address 1-D morphodynamics problems of engineering interest.

Syllabus

OPEN CHANNEL FLOW HYDRODYNAMICS (12 lectures) - Uniform flow and bulk momentum balance equations (e.g. Manning, Chezy); Bed shear stress (1L) - Cauchy Equation, Newtonian fluids, Viscous shear stress, Navier-Stokes equation (2L) - Introduction to turbulence (Reynolds experiments); Reynolds decomposition (mean and fluctuating components); Reynolds equations (2L). - Turbulent shear stress (Physical meaning); Reynolds equations for uniform open channel flows; Shear stress distribution in uniform flows (2L) - 1-D Modelling: Saint-Venant equations (depth averaged Reynolds equations); brief introduction to 2-D modelling; Closure problem in turbulent flows (1L); - Qualitative description of coherent structures in open channel flows and discussion about their importance in sediment transport: Sweep, Ejections, hairpin vortices, secondary currents (1L). - Roughness length, viscous length scale, viscous sub-layer, roughness Reynolds number , Hydraulically smooth, transitionally-rough and hydraulically rough open channel flows; Nikuradse experiments, Strickler scaling for grain roughness (1L). - Derivation of the log law of the wall (via eddy viscosity and dimensional analysys) (1L). - Flow around spheres and sediment grains: concept of drag and lift. (1L); SEDIMENT TRANSPORT (24 lectures) - Definition of key terms (terminal velocity, sediment diameter, grain size distribution, uniform and non-uniform sediment) (1L) - Incipient motion (Critical shear stress, dimensional analysis and Shields criterion; critical mean velocity, Yang’s criterion) (1.5L) - Design of stable channels (1.5L) - Resistance to flow and bed-forms (Einstein’s approach) (2L) - Bed-load transport (description, Du-Boys, Meyer-Peter Muller) (3L) - Suspended load transport (3L) - Total load transport (3L) - 1-Dimensional sediment transport modelling: Exner equation (1-D equilibrium bed profiles); brief introduction to 2-D Exner equation (1L). - Non uniform sediment transport formulas (1L); - Sediment transport modelling in Hec-Ras (1L); - Introduction; engineering problems related to bridge scour (1L) - General scour in contractions caused by piers and abutments (1L) - Turbulent flows around piers and abutments(1L) - Dimensional analysis(1L) - Predictive empirical equations for pier and abutment local scour: experiments, data analysis and uncertainty estimation.(2L)

Special Features

None

Learning and Teaching

Teaching and learning methods

The module is divided into 12 lectures devoted to open channel flow hydrodynamics, and 24 lectures devoted to sediment transport theory and applications. Lectures are interspersed with tutorials where students will be supported in the solution of numerical examples.

TypeHours
External visits3
Preparation for scheduled sessions14
Follow-up work28
Completion of assessment task30
Tutorial13
Revision30
Seminar6
Lecture14
Wider reading or practice12
Total study time150

Resources & Reading list

Yang C.T. (1996). Sediment Transport Theory and Practice. 

MaysL.W (2001). Water Resources Engineering Wiley. 

Tritton D.J. (2007). Physical Fluid Dynamics. 

Assessment

Summative

MethodPercentage contribution
Coursework 20%
Exam 80%

Referral

MethodPercentage contribution
Exam 100%

Repeat Information

Repeat type: Internal & External

Linked modules

Pre-requisites

To study this module, you will need to have studied the following module(s):

CodeModule
CENV2008Hydraulics
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