Numerische und experimentelle Analyse von Pumpeneinlässen

1. Numerical and Experimental Analyses of Pump Intakes
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Numerical and Experimental Analyses
of Pump Intakes
Aljaž Škerlavaj
Turboinštitut, Ljubljana, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
25. April 2013, Wien

2. Numerical and Experimental Analyses of Pump Intakes
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________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 2 / 20
Fluid Flow in Pump Intakes
IMPELLER
Testing:
1.) vortices
2.) swirl angle
3.) axial velocity distr.
PUMP SUMP / INTAKE

3. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 3 / 20
IMPELLER
PUMP SUMP / INTAKE
Testing:
1.) vortices
2.) swirl angle
3.) axial velocity distr.
Rechannel, model, typical = 8000
Rebell, model, typical = 8E+04
PUMP BELL
Fluid Flow in Pump Intakes

4. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 4 / 20
Consequences of vortices
• Vibrations and noise
• Extreme consequences:
Case 1: submerged vortices Case 2: Air-entraining vortices

5. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 5 / 20
(Experimental) Model studies
• Initial geometry design: recommendations, based
on experience
• Properly conducted physical model study is
momentary the only reliable method to prove good
sump design or to identify unacceptable flow
patterns at the pump inlet for a given sump design
• Geometrical similarity, dynamic similarity – Froude
number
• Needs for model studies:
– Improving of existing ("old") pump sumps by introducing
the remedial measures
– Checking of new designs

6. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 6 / 20
Hydraulic model of pump sump

7. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 7 / 20
Hydraulic model - details

8. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 8 / 20
Numerical simulations
• Numerical simulations of pump intakes should be reliable
• Short-term perspective: to assist the physical models
• Long-term perspective: to replace physical model testing
• A prescription of a turbulence model has a large influence on
result of the simulation
• Majority of numerical simulations use k-ε or k-ω turbulence
models (lately some of them use LES)
• The first case of using (quality) LES: Tokyay and
Constantinescu (2005)
– SST steady state simulation vs. LES (unsteady simulation)
– unequal meshes: 1 million el. for SST, 5 million el. for LES
– LES: good agreement with measurement data (velocity, TKE),
measured by Yulin et al. (2000)

9. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 9 / 20
Governing equations
• Navier-Stokes equations (const. viscosity and density):
• Variable decomposition:
a) Time averaging – RANS equations:
b) Filtering – LES:
0 ,j
j
u
x



2
0
0
1i i i
j
j i j j
u u up
u
t x x x x
  
    
     
A A A 
0 ,j
j
u
x



2
0
0
1 i ji i i
j
j i j j j
u u up
u
t
u
x x x x
u
x
  
     
    
 


2
0
0 0
11
R
ij
j
i i i
j
j i j j
u u up
u
t x xx x x
  
     
    

 
0 ,j
j
u
x



     , , , d
D
A t G A t x r x x r r
0
0
1 t t
i it
A Adt
t


 

10. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 10 / 20
Geometry
Rebell = 1.7E+05
Repipe = 2.1E+05
D = 0.1298 m
Dbell = 0,16 m
Wduct = 0.193 m
H = 0.247 m
Ubell = 1.07 m/s
Two inlet channels with
unequal flow rates
Source: (Škerlavaj et al., 2011)

11. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 11 / 20
Setup of numerical model
• One computational mesh for all turbulence models
tested (block-structured, 35 million el.)
• Ansys CFX
• Steady-state and transient numerical simulations
• Turbulence models: SST, SAS (v. 2005 and 2007),
SSG RSM, BSL EARSM, DES, LES
• Curvature correction (CC): SST, SAS
• Time-step size: equal (i.e, small) in all simulations
Source: (Škerlavaj et al., 2011)

12. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 12 / 20
Computation time
Source: (Škerlavaj et al., 2011)

13. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 13 / 20
Results (velocity, TKE)
SST
SST-CC
SAS
SAS-CC
LES
Source: (Škerlavaj et al., 2011); Source of experiment: (Tokyay and Constantinescu, 2006), with permission from ASCE
Velocity TKE

14. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 14 / 20
SST
SAS
SST-CC
LES
SAS-CC
Results (vortical structures)
DES
Source: (Škerlavaj et al., 2011)
Q=50000 s-2 Q=500000 s-2
Q=50000 s-2 Q=500000 s-2
 1
2
ij ij ij ijQ S S Ω Ω

15. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 15 / 20
SAS-CC,25mil.el.
Results (SAS-CC)
Source: (Škerlavaj et al., 2011); Source of experiment: (Tokyay and Constantinescu, 2006), with permission from ASCE

16. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 16 / 20
L2 L1
L3 L4
SAS-CC, 25 mil. el.
Results (SAS-CC model)
Source: (Škerlavaj et al., 2011); Source of experiment: (Tokyay and Constantinescu, 2006), with permission from ASCE

17. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 17 / 20
Conclusions
• A combination of physical and numerical model (CFD)
seems an optimal combination for quality design of
pump intakes
• Benefits of experiment: easy to perform experiments
with geometry variations, easy to observe free-surface
vortices
• CFD: prediction of floor vortex can be very accurate
(depending on turbulence model):
– SAS-CC: good agreement with LES and with measurements
– DES: (less suitable for industrial cases than SAS), good result
– 2-eq. RANS: usage of CC is necessary
– SST-CC: in the upper part of the vortex the shape is not
predicted well
– RSM in EARSM: slow convergence rate, long computation time

18. Numerical and Experimental Analyses of Pump Intakes
________________________________________________________________________________________________________________________
________________________________________________________________________________________________________________________
www.turboinstitut.si info@turboinstitut.si,
1000 Ljubljana, Rovšnikova 7, Slovenia
ANSYS conference & CADFEM Austria Users’ Meeting
Wien, 25. April 2013 Slide 18 / 20
References
• Geometry and published measurements:
– Tokyay TE, Constantinescu SG (2006). Validation of large-eddy
simulation model to simulate flow in pump intakes of realistic
geometry. Journal of Hydraulic Engineering 132(12),1303-1315.
– Tokyay TE, Constantinescu SG (2005). Large eddy simulation and
Reynolds averaged Navier-Stokes simulations of flow in a realistic
pump intake: a validation study. Proceedings of the World Water and
Environmental Resources Congress. Anchorage, Alaska, USA.
• Measurements:
– Yulin W, Yong L, Xiaoming L (2000). PIV experiments on flow in a
model pump suction sump. Research report, Beijing: Tsinghua
University.
• Our results:
– Škerlavaj A, Škerget L, Ravnik J, Lipej A (2011). Choice of a
turbulence model for pump intakes. Proceedings of the IMechE, Part
A: Journal of Power and Energy 225(6),764-778.

19. Numerical and Experimental Analyses of Pump Intakes
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Thank you for your attention!

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