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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling 1 Miguel R. Silva MSc Student, IST António N. Pinheiro Full Professor, IST

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Introduction Throughout the design and planning for hydraulic structures as, engineers and researchers are increasingly integrating computational fluid dynamics () into the process. Throughout the design and planning for hydraulic structures as spillways, engineers and researchers are increasingly integrating computational fluid dynamics (CFD) into the process. Velocity magnitude in a labyrinth weir (Lan, 2010) Despite reports of success in the past, there is still no comprehensive assessment that assigns ability to CFD models to simulate a wide range of different spillways configurations. In this study, the applicability of CFD model (FLOW-3D) to simulate the flow into a geometry complex spillway was reviewed. 1

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Case study Salamonde dam, located in the north of Portugal in river Cávado, Peneda Gerês National Park, is a double-curved arch dam in concrete with maximum height of 75 m from foundations. The present spillway is composed by four surface orifices controlled by gates. Salamonde Dam (from INAG and CNPGB) Present spillway in Salamonde Dam (from origens.pt) After safety analysis from (EDP, 2006), it was concluded that it would be necessary an additional discharge structure - complementary spillway for Salamonde dam (under construction), which is the case study in this presentation. 2

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Case study The complementary spillway of Salamonde dam (under construction), is a gated spillway, controlled by an ogee crest, followed by a tunnel with rather complex geometry, designed for free surface flow, and a ski jump structure which directs the jet into the river bed. Inlet structure (from AQUALOGUS) The ogee crest is divided into two spans controlled by radial gates, 6.5 m wide. Design characteristics: Design discharge – 1233 m 3 /s 1 Inlet structure (from AQUALOGUS) 3

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Inlet sctructure Tunnel Cross section AA Cross section CC Cross section BB Case study 4

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Outlet structure Cross section AA Cross section BB Case study The outlet structure is a ski jump, producing a free jet with impinging region in the center of the river bed. Along the last 28 m of the outlet structure, the flow section is progressively reduced. 5

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Objectives Calibrating the computational model, providing a sensitive analysis for some of the main parameters/models in FLOW-3D such as: Momentum advection model ( 1 st order vs 2 nd order with monotonicity preserving) VOF method (Defaut One fluid, free surface vs Split Lagragian Method) Turbulence mixing length (TLEN) parameter Cell size Validating the computational model using physical model discharge and flow depths measurements Assessing the computational model results for design conditions, and compare them with physical model. The assessed results were: Fluid depth Velocity Pressure at outlet structure Free jet impinging region 6

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Physical Model Inlet structure from upstream view (from LNEC) The spillway was primarily tested and developed in a physical model built in Portuguese National Laboratory for Civil Engineering (LNEC), where discharge and flow depth were measured in ten cross-sections for five different gate openings. Additionally, the pressure at some points of the bottom and side walls of the outlet structure were measured. Inlet structure from downstream view (from LNEC) 7

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Physical Model Location of the ten cross-sections for flow depth measurements (from LNEC) 8

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Numerical Model 5 components: 1.Terrain 2.Inlet structure 3.Gates 4.Tunnel (hole component) 5.Outlet structure Geometry 1 flux surface baffle: 1 flux surface baffle downstream of tunnel (aligned with x axis) for discharge calculation Initial conditions: - Hydrostatic pressure in z direction - Initial fluid elevation at reservoir and river bed river bed 9 hole component

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Numerics: Volume-of-fluid advection: Default VOF and Split Lagrangian VOF Momentum advection: 1st order and 2nd order monotonicity preservingPhysics: Gravity g = m/s 2 in z direction Viscosity and turbulence: RNG model No-slip Model setup Numerical Model 10 Main features of the computer used in simulations: Processor: Intel® Core i QM 2.30GHz 8GB DDR Memory

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Boundary Conditions: Specified Pressure at reservoir mesh block (Y Max, X Max and X Min)Specified Pressure at reservoir mesh block (Y Max, X Max and X Min) Specified Pressure upstream of the river (X Max)Specified Pressure upstream of the river (X Max) Outflow downstream of the river (X Min and Y Min)Outflow downstream of the river (X Min and Y Min) Symmetry between mesh blocksSymmetry between mesh blocks 5 Mesh blocks: Cubic cellsCubic cells 1 Nested block at inlet structure and tunnel1 Nested block at inlet structure and tunnel 4 auxiliary solids to block unnecessary active cells4 auxiliary solids to block unnecessary active cells Meshing Numerical Model 11 auxiliary solids Nested block

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Notes: Every simulations were considered with a 1,0 m cell size* and for 200 seconds (exception in Cell size analysis).Every simulations were considered with a 1,0 m cell size* and for 200 seconds (exception in Cell size analysis). Results of flow rate presented are calculated as a average value after steady state was reachedResults of flow rate presented are calculated as a average value after steady state was reached Laminar regime was considered until TLEN parameter analysisLaminar regime was considered until TLEN parameter analysis VOF default method was considered until VOF method analysisVOF default method was considered until VOF method analysis The model configurations under analysis were: 1.Momentum advection model ( 1 st order vs 2 nd order with monotonicity preserving (MP)) 2.VOF method (Default One fluid, free surface vs Split Lagragian Method) 3.Turbulence mixing length (TLEN) parameter 4.Cell size Sensitive analysis - Discharge 3 flow conditions were considered by setting the level in the reservoir: * Coarsest mesh to start 12

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Momentum advection model (1 st order vs 2 nd order with MP) VOF method (Default One fluid, free surface vs Split Lagragian Method) 2 nd order with monotonicity preserving Default VOF method One fluid, free surface Sensitive analysis - Discharge 13

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 For a 1,0 m cell size, spillway discharge didnt appear to be very sensitive to TLEN parameter, although it influences the duration and stability of the simulation Turbulence mixing length (TLEN) parameter TLEN 7% of hydraulic diameter 0.4 m Region not relevant to the spillway flow Sensitive analysis - Discharge 14 Dynamically computed TLEN

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Cell size For somehow accurate flow rate results, 0.50 m cell size is enough *Restart Simulation of 30 seconds from 1.0m cell size simulation Computational real time was drastically increased with 0.25 m cell size. For flow rate results, the increase in computational time didn't justify the increased accuracy of a 0.25 m mesh. Sensitive analysis - Discharge 15

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Sensitive analysis - Fluid depth The model configurations under analysis were: 1.Cell size 2.VOF method (Default One fluid, free surface vs Split Lagragian Method) 3.Turbulence mixing length (TLEN) parameter 1 flow condition was considered by enabling the gates solid component for a 2.0 m opening Notes: 1.TLEN parameter considered was 0.4m 2.The presented results are related to Restart Simulations from steady state conditions Q Physical Model = m 3 /s 16

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Cell size Section 1 Section 2 Section 3 Section 4 Section 5 Section 6 Sensitive analysis - Fluid depth Physical Model 1.00 m cell size 0.50 m cell size 0.25 m cell size

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Conclusion: 0.25 m cell size to represent with greater detail the free surface and flow rate accuracy for gate opening conditions Cell size Cell size = 1.00 m: Q FLOW-3D (m 3 /s) = % errorQ FLOW-3D (m 3 /s) = % error Computational time 2 hoursComputational time 2 hours Cell size = 0.50 m: Q FLOW-3D (m 3 /s) = % errorQ FLOW-3D (m 3 /s) = % error Computational time 2 hours*Computational time 2 hours* Cell size = 0.25 m: Q FLOW-3D (m 3 /s) = % errorQ FLOW-3D (m 3 /s) = % error Computational time 61 hours*Computational time 61 hours* *Restart Simulation of 30 seconds Section 7 Section 8 Section 9 Section 10 Sensitive analysis - Fluid depth m cell size; 0.50 m cell size 0.25 m cell size

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Split Lagragian VOF: Q (m 3 /s) = 258.0Q (m 3 /s) = Relative error = -3.4 %Relative error = -3.4 % Computational time 107 hoursComputational time 107 hours Default VOF: Q (m 3 /s) = 258.2Q (m 3 /s) = Relative error = -3.3 %Relative error = -3.3 % Computational time 61 hoursComputational time 61 hours VOF method (Default One fluid, free surface vs Split Lagragian Method) Section 6 Section 1 Section 4 Conclusion: Default VOF method for lower computational time Sensitive analysis - Fluid depth Default VOF Split Lagragian VOF Physical Model

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Conclusion: TLEN adjusted in live simulation time (values lower than 0.4 m) for lower computational time Turbulence mixing length (TLEN) parameter Section 6 Section 1 Section 4 TLEN = dynamically computed: Q (m 3 /s) = % errorQ (m 3 /s) = % error Computational time 137 hoursComputational time 137 hours TLEN = 0.4 m: Q (m 3 /s) = % errorQ (m 3 /s) = % error Computational time 61 hoursComputational time 61 hours TLEN = 0.8 m: Q (m 3 /s) = % errorQ (m 3 /s) = % error Computational time 65 hoursComputational time 65 hours TLEN = 1.1 m: Q (m 3 /s) = % errorQ (m 3 /s) = % error Computational time 97 hoursComputational time 97 hours Sensitive analysis - Fluid depth 20 TLEN = 0.4 m TLEN = 0.8 m TLEN = 1.1 m TLEN = dyn. computed Physical Model

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Simulations and real computational time: 1 st simulation: cell size 0,50 m for 60 seconds -> Real time: 21 hours and 27 minutes1 st simulation: cell size 0,50 m for 60 seconds -> Real time: 21 hours and 27 minutes 2 nd simulation (Restart simulation): cell size 0,25 m for 10 seconds -> Real time: 17 hours and 5 minutes2 nd simulation (Restart simulation): cell size 0,25 m for 10 seconds -> Real time: 17 hours and 5 minutes FLOW-3D configurations: 2 nd order monotonicity preserving momentum advection2 nd order monotonicity preserving momentum advection Default VOF (One fluid, free surface)Default VOF (One fluid, free surface) RNG turbulence modelRNG turbulence model TLEN adjusted in real time (between 0,4 and 0,1 m)TLEN adjusted in real time (between 0,4 and 0,1 m) Cell size 0,50 m and 0,25 m for Restart simulationCell size 0,50 m and 0,25 m for Restart simulation Design conditions: Reservoir level = 270,64 mReservoir level = 270,64 m Q = 1233,0 m 3 /sQ = 1233,0 m 3 /s Results for Design Discharge Calculated flow in 60 seconds simulation Q FLOW-3D (m 3 /s) = % error 21

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Results for Design Discharge 22

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Section 9: V Dim. (m/s) = 25.88V Dim. (m/s) = V FLOW-3D (m/s) = % errorV FLOW-3D (m/s) = % error Velocity profiles: Section 4* Section 6* Section 9* Section 4: V Dim. (m/s) = 24.01V Dim. (m/s) = V FLOW-3D (m/s) = % errorV FLOW-3D (m/s) = % error Section 6: V Dim. (m/s) = 24.62V Dim. (m/s) = V FLOW-3D (m/s) = % errorV FLOW-3D (m/s) = % error Results for Design Discharge *Velocity profiles rendered from post-processing software EnSight

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Pressure diagrams: One of the greatest benefits of CFD models is the possibility to determine the main characteristics of the flow in any region of the computational domain. Pressure diagrams can be useful for the structural design of hydraulic structures. Section 5* Section 6* Section 10* Results for Design Discharge *Pressure diagrams rendered from post- processing software EnSight

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Pressure diagrams: The outlet structure has, naturally, higher values of pressure studied in Physical model. Pressure diagrams in the outlet structure (for each 5 m distance profile) – Rendered from EnSight Location of the pressure taps in the physical model (from LNEC) The pressure value was compared for 4 different points: 2 for the bottom wall and 2 for the right side wall P 2F P 1F P 2F P3P3P3P3 P1P1P1P1 P 1F Results for Design Discharge 25

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Conclusion: FLOW-3D appears to give accurate results of pressure Pressure diagram at m from downstream outlet structure limit Pressure diagrams: Pressure diagram at 2.00 m from downstream outlet structure limit Point 2F (higher pressure value in physical model): P Physical Modell (Pa) = P Physical Modell (Pa) = P FLOW-3D (Pa) = % errorP FLOW-3D (Pa) = % error Point 3: P Physical Modell (Pa) = P Physical Modell (Pa) = P FLOW-3D (Pa) = % errorP FLOW-3D (Pa) = % error Point 1F: P Physical Modell (Pa) = 97184P Physical Modell (Pa) = P FLOW-3D (Pa) = % errorP FLOW-3D (Pa) = % error P 2F P3P3P3P3 P1P1P1P1 P 1F Point 1: P Physical Modell (Pa) = 95419P Physical Modell (Pa) = P FLOW-3D (Pa) = % errorP FLOW-3D (Pa) = % error Results for Design Discharge 26

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Free jet: One of the main objectives of building the physical model of the Salamonde spillway was analyzing the free jet impinging region at the river bed. View of free jet from left hill (physical and computational models) View of free jet from top (physical and computational models) View of free jet from right hill (physical and computational models) Conclusion: FLOW-3D represents accurately the free jet shape Results for Design Discharge 27

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 FLOW-3D results of free jet incidence: L FLOW-3D Min = 48.5 m -1.0 % errorL FLOW-3D Min = 48.5 m -1.0 % error L FLOW-3D Max = 68.4 m % errorL FLOW-3D Max = 68.4 m % error Free jet: In the physical model, the Min. and Max. of free jet impinging was registered : L Physical Model Min = 49.0 mL Physical Model Min = 49.0 m L Physical Model Max = 91.0 mL Physical Model Max = 91.0 m *Rendered with EnSight Conclusion: FLOW-3D appears to be somehow accurate for free jet impinging region Results for Design Discharge 28 *Rendered with EnSight

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Water level fluctuations against the slopes of the valley: One of the major concern of engineers during the design of spillways with free jet dissipation is the increase of the level in the river hills. FLOW-3D could help to decide the jet impinging region in the river bed in order to minimize erosion and water level fluctuations against the slopes of the valley. For Salamonde, a 12 m elevation above the maximum river level was expected. Results for Design Discharge 29

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, A sensitive analysis for some main FLOW-3D configurations is quite important before starting to predict flow characteristics: 1.2 nd order momentum advection model with monotonicity preserving was a good choice for better accuracy without much more computational time 2.Split Lagragian VOF didnt appear to be useful in this kind of extreme velocity flow conditions 3.TLEN parameter has a huge importance in simulation stability and duration 4.Finer cell size has higher importance if there are some geometric details such as radial gates 2.In general, FLOW-3D accurately represents the flow along the spillway with rather complex geometry 3.FLOW-3D could be very useful for structural design of hydraulic structures. Pressure diagrams and velocity profiles could be rendered with a post-processing software as EnSight and could be helpful in that design phase. Conclusions 30

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Flow Science, Inc. support team : Melissa Carter and Jeff Burnham Simulaciones y Proyectos, SL : Francisco Garachana and Raúl Martín Ensight support team, Distene support and ANALISIS-DSC support : Daniel Cuadra EDP AQUALOGUS LNEC: Lúcia Couto, Teresa Viseu and António Muralha Instituto Superior Técnico: Prof. António Pinheiro Acknowledgments 31

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Complementary spillway of Salamonde dam. Physical and 3D numerical modeling Miguel R. Silva; António N. PinheiroJune 13, 2013 Any Questions? 32 Miguel R. Silva MSc Student, IST António N. Pinheiro Full Professor, IST

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