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Numerical simulation of three-dimensional flows in water storage tanks - Application to Norra Ugglarps Reservoirs in South Sweden

Jaunâtre, Julien LU (2013) In TVVR13/5010 VVR820 20131
Division of Water Resources Engineering
Abstract
The main purpose of this thesis was to simulate the three-dimensional flow patterns in tanks for water storage. The practical intentions of the simulations were to identify water-quality problems related to insufficient water exchange. The water storage reservoirs at Norra Ugglarp in South Sweden were investigated as a special case study. In this thesis, the open source CFD software OpenFoam was chosen to simulate flow features in tanks.
The first part of this thesis focused on developing an understanding of the case study; that is, the distribution of water in West Skåne and especially the functioning of Norra Ugglarps reservoirs. An overview of possible mixing problems in the tank was detailed and presented.
As modelling was chosen... (More)
The main purpose of this thesis was to simulate the three-dimensional flow patterns in tanks for water storage. The practical intentions of the simulations were to identify water-quality problems related to insufficient water exchange. The water storage reservoirs at Norra Ugglarp in South Sweden were investigated as a special case study. In this thesis, the open source CFD software OpenFoam was chosen to simulate flow features in tanks.
The first part of this thesis focused on developing an understanding of the case study; that is, the distribution of water in West Skåne and especially the functioning of Norra Ugglarps reservoirs. An overview of possible mixing problems in the tank was detailed and presented.
As modelling was chosen to identify mixing problems, mechanisms and equations about flow modelling were first discussed before going into the OpenFOAM software itself. The modelling strategy in OpenFoam do not differs from other CFD software; nevertheless, setting up the case and post processing the results were quite unusual and discussed in some detail.
When it came to the modelling itself, in order to become familiar with the software, some simple test setups were first explored in two-dimensional tanks of simple geometry. Then, the simulations were extended to three-dimensional situations, still for rectangular tanks. Finally, the software was employed to simulate the flow in the reservoirs at Norra Ugglarp.
From the modelling results, it was possible to derive the following conclusions. The incoming velocity is a key parameter as injection of water should be powerful enough to reach the surface and renew the upper layer water. Water level range is another important parameter to renew more volume in the tanks. All conclusions tend to prove that the reservoirs at Norra Ugglarp suffer from insufficient mixing, mainly due to both the weak incoming velocity of new water and the limited water level range in use.
Thus, solutions to alleviate poor mixing are presented, such as increasing the water level range or monitoring existing valves to ameliorate the filling regarding water circulation. (Less)
Abstract (Swedish)
Det huvudsakliga syftet med detta arbete var att simulera tredimensionella flödesmönster i tankar för lagring av vatten. De praktiska avsikter med simuleringarna var att identifiera vattenkvalitetsproblem relaterade till bristande vattenutbyte. De vattenmagasin som reservoarer vid Norra Ugglarp i Skåne utgör undersöktes i en särskild fallstudie. I denna avhandling har den öppna CFD källkoden OpenFOAM valts för att simulera cirkulationen i tankarna.
Den första delen av rapporten fokuserar på en detaljerad förståelse av fallstudien, som omfattar fördelningen av vatten i västra Skåne och särskilt funktionen hos Norra Ugglarps reservoarer. En översikt över möjliga omblandningsproblem i reservoarerna studerades i detalj och sammanfattades.
... (More)
Det huvudsakliga syftet med detta arbete var att simulera tredimensionella flödesmönster i tankar för lagring av vatten. De praktiska avsikter med simuleringarna var att identifiera vattenkvalitetsproblem relaterade till bristande vattenutbyte. De vattenmagasin som reservoarer vid Norra Ugglarp i Skåne utgör undersöktes i en särskild fallstudie. I denna avhandling har den öppna CFD källkoden OpenFOAM valts för att simulera cirkulationen i tankarna.
Den första delen av rapporten fokuserar på en detaljerad förståelse av fallstudien, som omfattar fördelningen av vatten i västra Skåne och särskilt funktionen hos Norra Ugglarps reservoarer. En översikt över möjliga omblandningsproblem i reservoarerna studerades i detalj och sammanfattades.
Modellering valdes för att identifiera omblandningsproblem samt grundläggande mekanismer och ekvationer för flödesmodelleringen diskuteras först innan man går in på själva programvaran OpenFOAM. Modelleringsstrategin i OpenFOAM skiljer sig inte nämnvärt från annan CFD-programvara, även om upprättandet av det studerade fallet och efterbearbetningen av resultaten var ganska ovanligt, vilket speciellt diskuteras i rapporten.
Vad gäller själva modelleringen, för att bli bekant med programmet, har några enkla testuppställningar först utforskats omfattande två-dimensionella tankar av enkel geometri. Därefter utsträcktes simuleringarna till tre-dimensionella situationer för rektangulära tankar. Slutligen användes programvaran för att simulera flödet i Norra Ugglarps reservoarer.
Från modelleringsresultaten var det möjligt att erhålla följande slutsatser. Hastigheten hos den inkommande strålen är en viktig parameter och den bör vara tillräckligt hög så att strålen kan nå ytan och förnya övre vattenskikt. Variationen i vattennivå är en annan viktig parameter för att förnya volymen i tankarna. Resultaten från föreliggande beräkningar visar att Norra Ugglarps reservoirer lider av dålig omblandning, främst på grund av den låga hastigheten hos den inkommande strålen av nytt vatten och den begränsade variationen i vattennivå.
Lösningar för att förbättra omblandningen presenteras, till exempel att öka variationen i vattennivå och att övervaka befintliga ventiler för att förbättra fyllningsprocessen med avseende på vattencirkulationen. (Less)
Please use this url to cite or link to this publication:
author
Jaunâtre, Julien LU
supervisor
organization
course
VVR820 20131
year
type
H2 - Master's Degree (Two Years)
subject
keywords
drinking water storage tank, rectangular tank, Computational Fluid Dynamics (CFD), numerical modelling, 2D, 3D flow, cluster, Lunarc, dricksvatten ackumulatortank, rektangulär tank, numerisk modellering, 3D flöde, kluster, Lunarc.
publication/series
TVVR13/5010
report number
13/5010
ISSN
1101-9824
language
English
additional info
Examiner: Rolf Larsson
id
4172871
date added to LUP
2013-11-21 14:50:18
date last changed
2019-03-29 11:30:17
@misc{4172871,
  abstract     = {The main purpose of this thesis was to simulate the three-dimensional flow patterns in tanks for water storage. The practical intentions of the simulations were to identify water-quality problems related to insufficient water exchange. The water storage reservoirs at Norra Ugglarp in South Sweden were investigated as a special case study. In this thesis, the open source CFD software OpenFoam was chosen to simulate flow features in tanks. 
The first part of this thesis focused on developing an understanding of the case study; that is, the distribution of water in West Skåne and especially the functioning of Norra Ugglarps reservoirs. An overview of possible mixing problems in the tank was detailed and presented. 
As modelling was chosen to identify mixing problems, mechanisms and equations about flow modelling were first discussed before going into the OpenFOAM software itself. The modelling strategy in OpenFoam do not differs from other CFD software; nevertheless, setting up the case and post processing the results were quite unusual and discussed in some detail.
When it came to the modelling itself, in order to become familiar with the software, some simple test setups were first explored in two-dimensional tanks of simple geometry. Then, the simulations were extended to three-dimensional situations, still for rectangular tanks. Finally, the software was employed to simulate the flow in the reservoirs at Norra Ugglarp.
From the modelling results, it was possible to derive the following conclusions. The incoming velocity is a key parameter as injection of water should be powerful enough to reach the surface and renew the upper layer water. Water level range is another important parameter to renew more volume in the tanks. All conclusions tend to prove that the reservoirs at Norra Ugglarp suffer from insufficient mixing, mainly due to both the weak incoming velocity of new water and the limited water level range in use.
Thus, solutions to alleviate poor mixing are presented, such as increasing the water level range or monitoring existing valves to ameliorate the filling regarding water circulation.},
  author       = {Jaunâtre, Julien},
  issn         = {1101-9824},
  keyword      = {drinking water storage tank,rectangular tank,Computational Fluid Dynamics (CFD),numerical modelling,2D,3D flow,cluster,Lunarc,dricksvatten ackumulatortank,rektangulär tank,numerisk modellering,3D flöde,kluster,Lunarc.},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVVR13/5010},
  title        = {Numerical simulation of three-dimensional flows in water storage tanks - Application to Norra Ugglarps Reservoirs in South Sweden},
  year         = {2013},
}