Complementary spillway of Salamonde dam. Physical and 3D numerical modeling 1 Miguel R. Silva MSc...

Complementary spillway of Salamonde dam.Physical and 3D numerical modeling

1

Miguel R. SilvaMSc Student, IST

[email protected]

António N. PinheiroFull Professor, IST

[email protected]

mailto:[email protected]


Complementary spillway of Salamonde dam. Physical and 3D numerical modeling

Miguel R. Silva; António N. Pinheiro

June 13, 2013

Introduction

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.

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June 13, 2013

Case studySalamonde 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.

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June 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 m3/s

• 1

Inlet structure (from AQUALOGUS)

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June 13, 2013

Inlet sctructure

Tunnel

Cross section AA’ Cross section CC’Cross section BB’

Case study

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June 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.

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June 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 ( 1st order vs 2nd 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

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June 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)

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June 13, 2013

Physical Model

Location of the ten cross-sections for flow depth measurements (from LNEC)

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June 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

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hole component



June 13, 2013

Numerics:

Volume-of-fluid advection:

Default VOF and

Split Lagrangian VOF

Momentum advection:

1st order and

2nd order monotonicity preserving

Physics:

Gravity g = -9.81 m/s2 in z direction

Viscosity and turbulence: RNG model

No-slip

Model setup

Numerical Model

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Main features of the computer used in simulations:

• Processor: Intel® Core™ i7-36010QM CPU @ 2.30GHz

• 8GB DDR3-1600 Memory



June 13, 2013

Boundary Conditions:

• Specified Pressure at reservoir mesh block (Y Max,

X Max and X Min)

• Specified Pressure upstream of the river (X Max)

• Outflow downstream of the river (X Min and Y Min)

• Symmetry between mesh blocks

5 Mesh blocks:

• Cubic cells

• 1 Nested block at inlet

structure and tunnel

• 4 auxiliary solids to “block”

unnecessary active cells

Meshing

Numerical Model

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auxiliary solids

Nested block



June 13, 2013

Notes:

• 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 reached

• Laminar regime was considered until TLEN parameter analysis

• VOF default method was considered until VOF method analysis

The model configurations under analysis were:

1. Momentum advection model ( 1st order vs 2nd 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:

Reservoir level

QPhysical Model

(m) (m3/s)

260.43 100.0262.47 250.0267.05 750.0

* Coarsest mesh to start

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June 13, 2013

Momentum advection model (1st order vs 2nd order with MP)

VOF method (Default → One fluid, free surface vs Split Lagragian Method)

Reservoir level

1st order Mom. Adv

2nd order Mom. Adv with MP

(m)

260.43 01:22:48 01:30:03262.47 01:08:01 01:21:07267.05 01:48:32 02:05:46

(hours:minutes:seconds)

Reservoir level

QPhysical Model

(m) (m3/s)QFLOW-3D

(m3/s)Error (%)

QFLOW-3D

(m3/s)Error (%)

260.43 100.0 81.9 -18.1 83.3 -16.7262.47 250.0 223.1 -10.8 224.9 -10.0267.05 750.0 690.3 -8.0 696.9 -7.1

1st order Mom. Adv2nd order Mom.

Adv with MP

2nd order with monotonicity preserving

Reservoir level

QPhysical Model

(m) (m3/s)QFLOW-3D

(m3/s)Error (%)

QFLOW-3D

(m3/s)Error (%)

260.43 100.0 83.3 -16.7 84.2 -15.8262.47 250.0 224.9 -10.0 223.6 -10.6267.05 750.0 696.9 -7.1 698.7 -6.8

One fluid, free surface VOF (Deafult)

Split Lagragian VOF

Reservoir level

One fluid, free surface VOF (Deafult)

Split Lagragian VOF

(m)

260.43 01:30:03 02:58:56262.47 01:21:07 01:48:41267.05 02:05:46 04:23:15


Default VOF method → One fluid, free surface


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June 13, 2013

For a 1,0 m cell size, spillway discharge

didn’t 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


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TLEN Computational real time TLEN Computational real time

(m) (hours:minutes:seconds) (m) (hours:minutes:seconds)

Dyn. Computed 02:04:54 0.8 02:36:410.3 01:33:04 0.9 03:31:110.4 01:42:41 1.0 04:00:440.5 03:21:07 1.1 04:08:120.6 04:48:27 1.5 07:47:13

Dynamically computed TLEN



June 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.


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Reservoir level

QPhysical

Model

(m) (m3/s)QFLOW-3D

(m3/s)Error (%)

QFLOW-3D

(m3/s)Error (%)

QFLOW-3D

(m3/s)Error (%)

260.43 100.0 82.7 -17.3 85.5 -14.5 90.1 -9.9262.47 250.0 222.6 -11.0 228.4 -8.6 235.2 -5.9267.05 750.0 691.3 -7.8 701.1 -6.5 729.6 -2.7

Cell size: 1.0m Cell size: 0.50m Cell size: 0.25m

Reservoir level

Cell size: 1.0m Cell size: 0.50m Cell size: 0.25m

(m)

260.43 01:04:59 00:53:41* 20:18:21*262.47 01:22:20 01:35:02* 24:19:40*267.05 01:42:41 02:03:44* 45:07:14*




June 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

QPhysical Model = 267.0 m3/s

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June 13, 2013

Cell size

Section 1

Section 2

Section 3

Section 4

Section 5

Section 6


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104 5 63 87

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• Physical Model• 1.00 m cell size• 0.50 m cell size• 0.25 m cell size



June 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:

• QFLOW-3D (m3/s) = 207.8 → -22.2% error

• Computational time ≈ 2 hours

Cell size = 0.50 m:

• QFLOW-3D (m3/s) = 239.2 → -10.4% error

• Computational time ≈ 2 hours*

Cell size = 0.25 m:

• QFLOW-3D (m3/s) = 259.5 → -2.8% error

• Computational time ≈ 61 hours*

*Restart Simulation of 30 seconds

Section 7

Section 8

Section 9

Section 10


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104 5 63 87

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1.00 m cell size; 0.50 m cell size 0.25 m cell size



June 13, 2013

Split Lagragian VOF:

• Q (m3/s) = 258.0

• Relative error = -3.4 %


Default VOF:

• Q (m3/s) = 258.2

• Relative error = -3.3 %


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


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104 5 63 87

9

• Default VOF• Split Lagragian VOF

• Physical Model



June 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 (m3/s) = 260.7 → -2.4% error


TLEN = 0.4 m:

• Q (m3/s) = 258.2 → -3.3% error


TLEN = 0.8 m:

• Q (m3/s) = 259.5 → -2.8% error


TLEN = 1.1 m:

• Q (m3/s) = 257.8 → -3.5% error



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• TLEN = 0.4 m• TLEN = 0.8 m• TLEN = 1.1 m• TLEN = dyn. computed

• Physical Model

1 2 104 5 63 87 9



June 13, 2013

Simulations and real computational time:

• 1st simulation: cell size 0,50 m for 60 seconds -> Real

time: 21 hours and 27 minutes

• 2nd simulation (Restart simulation): cell size 0,25 m for

10 seconds -> Real time: 17 hours and 5 minutes

FLOW-3D configurations:

• 2nd order monotonicity preserving momentum advection

• Default VOF (One fluid, free surface)

• RNG turbulence model

• TLEN adjusted in real time (between 0,4 and 0,1 m)

• Cell size 0,50 m and 0,25 m for Restart simulation

Design conditions:

• Reservoir level = 270,64 m

• Q = 1233,0 m3/s

Results for Design Discharge

Calculated flow in 60 seconds simulationQFLOW-3D (m3/s) = 1206.5 → -2.15% error

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June 13, 2013


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June 13, 2013

Section 9:

• VDim. (m/s) = 25.88

• VFLOW-3D (m/s) = 23.59 → -8.85 % error

Velocity profiles:

Section 4*

Section 6*

Section 9*

Section 4:

• VDim. (m/s) = 24.01

• VFLOW-3D (m/s) = 21.50 → -10.45 % error

Section 6:

• VDim. (m/s) = 24.62

• VFLOW-3D (m/s) = 21.88 → -11.13 % error


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1 210

4 5 63 87 9

*Velocity profiles rendered

from post-processing

software EnSight



June 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*


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1 210

4 5 63 87 9

*Pressure diagrams

rendered from post-

processing software

EnSight



June 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

P2F P1F

P2F

P3 P1

P1F


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June 13, 2013

Conclusion: FLOW-3D appears to give accurate

results of pressure

Pressure diagram at 10.20 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):

• PPhysical Modell (Pa) = 158181

• PFLOW-3D (Pa) = 158747 → 0.4 % error

Point 3:


• PFLOW-3D (Pa) = 120961→ -8.8 % error

Point 1F:


• PFLOW-3D (Pa) = 91585 → -5.8 % error

P2F

P3

P1

P1F

Point 1:


• PFLOW-3D (Pa) = 73220→ -23.3 % error


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June 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


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June 13, 2013

FLOW-3D results of free jet incidence:

• LFLOW-3D Min = 48.5 m → -1.0 % error

• LFLOW-3D Max = 68.4 m → -24.9 % error

Free jet:

In the physical model, the Min. and Max. of free jet impinging was registered :

• LPhysical Model Min = 49.0 m

• LPhysical Model Max = 91.0 m

*Rendered with EnSight

Conclusion: FLOW-3D appears to be

somehow accurate for free jet

impinging region


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*Rendered with EnSight



June 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 .


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June 13, 2013

1. A sensitive analysis for some main FLOW-3D configurations is quite important before

starting to predict flow characteristics:

1. 2nd order momentum advection model with monotonicity preserving was a good

choice for better accuracy without much more computational time

2. Split Lagragian VOF didn’t 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

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June 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

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June 13, 2013

Any Questions?

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Miguel R. SilvaMSc Student, IST

[email protected]

António N. PinheiroFull Professor, IST

[email protected]



Complementary spillway of Salamonde dam. Physical and 3D numerical modeling 1 Miguel R. Silva MSc...

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