ANSYS: Numerical and experimental analysis of pump intakes
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This document discusses numerical and experimental analyses of pump intakes. It describes how physical model studies and computational fluid dynamics (CFD) simulations can be used to analyze fluid flow patterns and identify undesirable vortices. The document presents a case study where different turbulence models in CFD simulations, including LES, DES, and RANS models with curvature correction, were compared to experimental data to validate their ability to predict flow features like velocities and turbulent kinetic energy. The SAS-CC model showed good agreement with LES and experimental measurements.
ANSYS: Numerical and experimental analysis of pump intakes
- 1. Numerical and Experimental Analyses of Pump Intakes ________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________ 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 ________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________ 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 ________________________________________________________________________________________________________________________ ________________________________________________________________________________________________________________________ Thank you for your attention!
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