SEDIMENTATION BETWEEN PARALLEL PLATES By Yonas Kinfu Paulos BE, Anna University in ...

103 Pages·2010·4.46 MB·English

SEDIMENTATION BETWEEN PARALLEL PLATES
By
Yonas Kinfu Paulos
B. E., Anna University
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTERS OF APPLIED SCIENCE
in
THE FACULTY OF GRADUATE STUDIES
CIVIL ENGINEERING
We accept this thesis as conforming
to the required standard
THE UNIVERSITY OF BRITISH COLUMBIA
April 1991
© Yonas Kinfu Paulos, 1991
In presenting this thesis in partial fulfilment of th erequirements for an advanced
degree at the University o fBritish Columbia, I agree that the Librar yshall make it
freely available for reference an dstudy. I further agree that permission for extensive
copying of this thesis for scholarly purposes may be granted by the head of my
department or by his or her representatives. It iunsderstood that copying or
publication of this thesis for financial gain shall not be allowed without my written
permission.
Department of C\VJ\L € N G\C\)£EKUVlG|
The University of British Columbia
Vancouver, Canada
Date
DE-6 (2/88)
Abstract
Settling basins can be shortened by using a stack of horizonta lparallel plates which
develop boundary layers in which sedimentation can occur. The purpose of this study is
to examine the design parameters for such a system and to apply this approach to a fish
rearing channel in which settling length is strictly limited.
Flow between parallel rough and smooth plates has been modelled together with
sediment concentration profile. Accurate description o fboundary layer flow requires the
solution of Navier-Stokes equations, and due to the complexity of the equations to be
solved for turbulent flow some assumptions are made to relate the Reynold sstresses to
turbulent kinetic energy and turbulent energy dissipation rate. The simplified equations
are solved using a numerical method which uses the approach given by the TEACH
code. The flow parameters obtained from the turbulent flow model are used to obtain
the sediment concentration profile within the settling plates .Numerical solution of the
sedimentation process is obtained by adopting the general transport equation. The lower
plate is assumed to retain sediments reaching the bottom.
The design of a sedimentation tank for a fish rearing unit with high velocity of flow
has been investigated. The effectiveness of the sedimentation tank depends on th euni
formity of flow attained at the inlet, and experiments were conducted to obtain the most
suitable geometric system to achieve uniform flow distribution without affecting other
performances of the fish rearing unit. The main difficulties to overcome were the heavy
circulation present in the sedimentation tank and the clogging of the distributin gsys
tem by suspended particles. Several distributing systems were investigated, the best is
discussed in detail.
u
It was concluded that a stack o fhorizontal parallel plates can be used in fish rearing
systems where space is limited for settling sediments .Flow distribution along the vertical
at the entrance to the plates determines the efficiency of the sediment settling process and
a suitable geometrical configuration can be constructed to distribute the high velocity
flow uniformly across the vertical. Numerical modelling of sediment removal ratio for
flow between smooth and rough parallel plates has been calculated. The results show
that almost the same pattern of sediment deposition occurs for both the smooth-smooth
and rough-smooth plate arrangements.
m
Table of Contents
Abstract ii
List of Tables vii
List of Figures viii
List of Symbols x
Acknowledgement xiv
1 INTRODUCTION 1
2 THEORETICAL BACKGROUND 4
2.1 Fall Velocity 4
2.1.1 Factors affecting fall velocity 4
2.1.2 Theoretical equations 5
2.1.3 Empirical and Semi-empirical formulations 7
2.1.4 Experimental data for natural quartz grains 8
2.2 Sediment Transfer Coefficient 8
2.3 Flow and Sedimentation Models 13
2.3.1 Turbulent Flow Model 13
2.3.2 Sedimentation Model 1,7
3 PREVIOUS WORK ON SEDIMENTATION METHODS 23
3.1 High-rate Settlers 25
iv
3.1.1 Introduction 25
3.1.2 Different Types of High-rate Settlers 25
3.1.3 Discussion of Theoretical Study 28
3.2 Sedimentation Basins 28
3.2.1 Rectangular Sedimentation Basins 29
3.2.2 Vortex-type Sedimentation Basins 34
4 SETTING TANK FOR FISHERIES 37
4.1 Introduction 37
4.2 Components of the Sedimentation Unit 39
4.2.1 Inlet 39
4.2.2 Distributing System 41
4.2.3 The Settling Plate System 44
4.2.4 Control Weir Outlet 47
5 DEVELOPMENT OF THEORY 49
6 NUMERICAL MODELLING OF FLOW AND SEDIMENTATION 52
6.1 Physical Model and Boundary Conditions 52
6.2 Finite Difference Formulation 54
6.2.1 Control Volume Definition 54
6.2.2 Derivation of Finite Volume Equations 55
6.3 Solution Algorithm 58
6.4 Convergence Criteria ' 59
7 EXPERIMENTS 60
7.1 Objective of Experiments 60
7.2 Apparatus 61
v
7.3 Procedure 62
8 EXPERIMENTAL RESULTS 66
8.1 Computational result 69
9 CONCLUSIONS 78
Bibliography 82
Appendices ' 86
A Wall Function Treatment 86
A.l Smooth Wall 87
A.2 Rough Wall 88
B TEACH Code Solution Procedure 89
vi
List of Tables
2.1 The k-e model empirical constants . . 16
2.2 Transported quantity T and values 17
2.3 Sedimentation Model T and values 22
8.1 Experimental setup parameters 68
vn
List of Figures
2.1 Transport of sediment within elemental control volume 21
3.1 Ideal rectangular sedimentation basin 24
3.2 Tube Settlers 26
3.3 Tilted-Plate Separator 26
3.4 Lamella Separator 27
3.5 Salakhov-type Vortex Settling Basin 34
3.6 Cecen-type Vortex Settling Basin '. . . . 35
4.1 Side view of sedimentation unit 39
4.2 Inlet side view 40
4.3 Grated system side view . . .- 42
4.4 Sedimentation tank side view 43
4.5 Deflecting plate arrangement 43
6.1 Physical Model and Boundary Conditions 53
6.2 Control Volume Description 55
7.1 Experimental setup 63
7.2 Sediment feeding system 64
8.1 Deposition for free surface( 100mm) and smooth plate 70
8.2 Deposition for free surface( 100mm) and plate at mid depth 71
8.3 Deposition for free surface (50mm) and plate at mid depth 72
viii
8.4 Deposition for smooth and rough plates . . . 73
8.5 Deposition for different roughness plates 74
8.6 Flow between parallel plates 75
8.7 Flow between rough and smooth plate 76
8.8 Numerical result for sediment deposition 77
A.9 Grid point near wall 86
IX