Vitor Sousa IST UTL Inês Meireles UA Jorge Matos IST UTL Maria do Céu Almeida LNEC OUTLINE Introduction Experimental study Numerical code Numerical model implementation Conclusions 1 INTRODUCTION ID: 830519
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Slide1
NUMERICAL MODELLING OF AIR-WATER FLOW IN A VERTICAL DROP MANHOLE
Vitor SousaIST, UTLInês MeirelesUAJorge MatosIST, UTLMaria do Céu AlmeidaLNEC
Slide2OUTLINE
IntroductionExperimental studyNumerical codeNumerical model implementationConclusions
Slide31. INTRODUCTION
Dissolved oxygen concentration is one of the most relevant parameters used in water quality assessments, both in natural and artificial streams.In sewer drops, the presence, or absence, of dissolved oxygen is of significance in relation to the build-up or persistence of sulphides.Only a limited number of prototype or model studies involved the use of vertical drops in circular channels, conveying either clean water, polluted river water or wastewater.Up to date, numerical modelling of turbulence and air entrained generated aeration has been mainly focused on artificial aerators, such as bubble plums.
CFD –
Computer Fluid Mechanics
has emerged as na alternative research tool in several fields:
increasingly complete models and more efficient models
increase of the computational capability of personal computers
Slide42. EXPERIMENTAL STUDY
Slide52. EXPERIMENTAL STUDY
Slide63. NUMERICAL CODE
The commercial code FLOW-3D®, developed by Flow-Science, Inc, was selected for this research due to its particularly efficient, robust and accurate method to simulate free-surface flows.The Reynolds-Averaged Navier-Stokes (RANS) mixture equations are used in the theoretical model:
Slide73. NUMERICAL CODE
The code allows for independent mesh and geometry definition due to the FAVOR method. Single- or multi-block grids can be used to define the domain in FLOW-3D, where the geometry can be incorporated through: a “solid modeler,” which allows for the use of general quadratic functionsComputer-Aided-Design (CAD) filestopographic dataUnlike other codes, the FLOW-3D does not need to simulate the air flow over the free surface due to the
TruVOF
method. The
TruVOF
requires three key elements to be implemented, centred in the resolution of the function of the fraction of fluid through:
Slide84. NUMERICAL MODEL IMPLEMENTATION
RUN DRUN E
RUN F
Turbulence model
RNG
RNG
RNG
Model of air-entrainment activated
No
No
Yes
Number of active cells
9.9E+05
13.1E+05
9.3E+05
Minimum size of cells (mm)
2.5x2.5x5.0
2.5x2.5x2.0
1.9x2.5x2.0
Slide95. RESULTS
Slide109. CONCLUSIONS
The simulations performed in this study show that the use of a RNG model combined with the TruVOF method allows for an adequate overall representation of the flow features in terms of water depth and pressure headThe activation of the model of air-entrainment was found crucial for the accuracy of the simulation of the pressure head of the air-water flow along the invert of the outlet channel.The model chosen for this stage of the research is a simplified representation of many drainage systems where free drops exist at the manholes, particularly in older systems.The results show that the code seems to simulate air-water flows down vertical drops correctly, particularly its effect in terms of pressure head.
Slide11RISK ASSESSMENT OF SEWER CONDITION USING ARTIFICIAL INTELLIGENCE TOOLS Application to the SANEST sewer system
Vitor SousaIST, UTLJosé Pedro MatosIST, UTLNuno Marques AlmeidaIST, UTLJosé Saldanha MatosIST, UTL
http://www.toledoblade.com/Police-Fire/2013/07/06/Sewer-repairs-start-after-intersection-collapse-Copy.html