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Draft Tube calculations using OpenFOAM-1.5devand validation with FLINDT data

C. Devals, Y. Zhang and F.GuibaultÉcole Polytechnique de Montréal, Canada

T. Vu and B. NennemannAndritz Hydro, Pointe-Claire, Canada

6th OpenFOAM Workshop, June 13-16 2011, PennState University, USA

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Viscous flow simulations for hydraulic turbo-machinery design

Runner

Draft-tube

Spiralcasing

Context

Distributor

7/15/2019 Draft Tube Calculations Using OpenFOAM-1.5dev and Validation With FLINDT Data

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Previous work: 25th IAHR Symposium on Hydraulic Machinery and Systems

September 20-24, 2010, Timisoara, Romania Steady and unsteady flow computation in an elbow draft tube with

experimental validationT.C. Vu, C. Devals, Y. Zhang, B. Nennemann and F. GuibaultInternational Journal of Fluid Machinery and SystemsVol 4, No 1, January-March 2011

Context

Lt=0.5%DthLt=1%Dth Lt=0.25%Dth

7/15/2019 Draft Tube Calculations Using OpenFOAM-1.5dev and Validation With FLINDT Data

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Understand why the recovery coefficient for Phi=0.368 shows an importantdecrease for Lt=0.5%Dth.

Validate OpenFOAM RANS simulations for draft tube on hexahedralmeshes

Compare recovery coefficient χ prediction with experimental data

Objectives

7/15/2019 Draft Tube Calculations Using OpenFOAM-1.5dev and Validation With FLINDT Data

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Model draft tube test: FLINDT FLINDT is for FLow INvestigation in Draft Tubes Project (LMH-EPFL Switzerland) Throat diameter: Dth = 0.4 m Rotational speed: N=1000 RPM

Angular velocity: ϖ=104.66 Hz

Flow coefficient ϕ: 0.340, 0.360, 0.368, 0.380, 0.390 and 0.410

corresponding swirl: 0.332, 0.242, 0.214, 0.198, 0.149 and 0.076

Recovery coefficient

∆pstat static pressure difference between inlet andoutlet

Aref reference section area Aref=0.17538m2

Test Case Description

3

th R

Q

πϖ ϕ =

2

2

1

 

 

 

 ∆=

ref 

stat 

 A

Q

P

 ρ 

 χ 

7/15/2019 Draft Tube Calculations Using OpenFOAM-1.5dev and Validation With FLINDT Data

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Steady state Reynolds averaged Navier-Stokes equations

Newtonian fluid

turbulence model

126

1

10.89257.0

kg.m997

−−

−

==

=

smlam ρ 

 µ ν 

 ρ 

ε −k 

turblam

T 

U 

U U  I  p

U U 

ν ν ν 

ν  ρ 

+=

=⋅∇

∇+∇+−⋅∇=⊗⋅∇

0

))(()(

r

rrrr

Physical Properties and Models

 ρ ε 

 ρ 

 µ ν 

2k C muturbturb ==

lam

turbrel

 µ 

 µ  µ  =

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Boundary Conditions

Inletpressure

type zeroGradient

U, k

type profile1DfixedValue

fileName "profil-rr.csv"

epsilontype

turbulentMixingLengthDissipationRateInlet

mixingLength 0.0003285

U profile k profile

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Boundary Conditions

Outletpressure

type fixedMeanValuemeanValue 0

value uniform 0

U, k and epsilon

type zeroGradient

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Boundary Conditions

pierU

type fixedValue

value uniform (0 0 0)

p, k and epsilon

type zeroGradient

No slip Wall condition

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Boundary Conditions

mainU

type fixedValue

value uniform (0 0 0)

p, k and epsilon

type zeroGradient

No slip Wall condition

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Boundary Conditions

extU

type fixedValue

value uniform (0 0 0)

p, k and epsilon

type zeroGradient

No slip Wall condition

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Steady state (RANS) calculations (10000 iterations) Solver: SimpleFOAM Convection term discretization: normalized variable diagram (NVD)

scheme GammaV (between 0 and 1) Linear solver: PBiCG for all variables except P,

GAMG for P Turbulence model: k-epsilon Velocity inlet BC : axi-symmetrically averaged velocity measures Turbulence inlet BC: axi-symmetrically averaged k measures

4 turbulence length scales tested (epsilon) Convergence: tolerance of 1.e-6, relTol of 0.01 for all variables

Monitoring variable: pressure recovery factor

Numerical Model

2

2

1

 

 

 

 

∆=

ref 

stat 

 A

Q

P

 ρ 

 χ 

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Mesh investigation

Scheme GammaV investigation: ψ =0, ψ =0.5 and ψ =1GammaV is the improved version of the NVD gamma scheme(ψ =0 best accuracy and ψ =1 more robust)

Mixing length investigation: Lt=0.25%Dth, 0.5%Dth, 1.0%Dth and 5%Dth

Initial conditions investigation

Test Cases

# nodes # elements

CRS 288744 276560

STD 782283 757968

FINE 1875470 1830884

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Mesh investigation

Scheme GammaV investigation

Mixing length investigation

Initial conditions investigation

Test Cases

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Mesh investigation – GammaV 1

Standard mesh Fine meshCoarse mesh

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Mesh investigation – GammaV 1

Standard meshCoarse mesh Fine mesh

Phi=0.368

X=-0.25

Phi=0.380

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Mesh investigation – GammaV 1 – Phi=0.380

StaticPressure

AxialComponent

RadialComponent

Energy

TangentialComponent

CFDExperimental Data

Steady probe CFDExperimental Data

Steady probe

Fine meshCoarse mesh

202

207203

205

209

208

213

211 214

ct2ct1

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Mesh investigation

Scheme GammaV investigation

Mixing length investigation

Initial conditions investigation

Test Cases

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GAMMAV 0.5 GAMMAV 1.0GAMMAV 0.0

Scheme investigation – GammaV – Coarse mesh

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Mesh investigation

Scheme GammaV investigation

Mixing length investigation

Initial conditions investigation

Test Cases

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Mixing length investigation – Standard mesh – GammaV 1

Lt=0.25%Dth Lt=0.50%Dth Lt=1.00%Dth Lt=5.00%Dth

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Relative Viscosity – Lt=0.50%Dth Relative Viscosity – Lt=5.00%Dth

X=0.25

X=-0.20

X=-0.25

X=0.20

X=0.25

X=-0.20

X=-0.25

X=0.20

X=0.00 X=0.00

Mixing length investigation – Standard mesh – GammaV 1

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Mesh investigation

Scheme GammaV investigation

Mixing length investigation

Initial conditions investigation

Test Cases

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Initial condition investigation – Std mesh – GammaV 1 – Lt=0.25%Dth

Initial conditionsfrom no previous calculation

Initial conditionsfrom previous calculation

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Conclusions

Results are quite good compared to experimental data Results are not so sensitive to mesh resolution except for Phi=0.368 Results are sensitive to scheme Results are sensitive to initialization

Perspectives

Validation and comparison with OpenFOAM-1.6ext Runner and Draft-Tube calculations Unsteady cases Wall function investigation

Conclusions and Perspectives

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Thank you for your listening

Any questions?