0
Research Papers: Flows in Complex Systems

Experimental and Numerical Investigation of the Precessing Helical Vortex in a Conical Diffuser, With Rotor–Stator Interaction

[+] Author and Article Information
A. Javadi

Division of Fluid Dynamics,
Department of Applied Mechanics,
Chalmers University of Technology,
Göteborg SE-412 96, Sweden
e-mail: ardalan.javadi@chalmers.se

A. Bosioc

Assistant Professor
Department of Hydraulic Machinery,
University Politehnica Timişoara,
Bv. Mihai Viteazu, No. 1,
Timişoara Ro-300222, Romania
e-mail: alin.bosioc@upt.ro

H. Nilsson

Professor
Division of Fluid Dynamics,
Department of Applied Mechanics,
Chalmers University of Technology,
Göteborg SE-412 96, Sweden
e-mail: hani@chalmers.se

S. Muntean

Center for Advanced Research in
Engineering Sciences,
Romanian Academy—Timişoara Branch,
Bv. Mihai Viteazu, No. 24,
Timişoara Ro-300223, Romania
e-mail: seby@acad-tim.tm.edu.ro

R. Susan-Resiga

Professor
Department of Hydraulic Machinery,
University Politehnica Timişoara,
Bv. Mihai Viteazu, No. 1,
Timişoara Ro-300222, Romania
e-mail: romeo.resiga@upt.ro

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received May 12, 2015; final manuscript received April 5, 2016; published online June 8, 2016. Assoc. Editor: Bart van Esch.

J. Fluids Eng 138(8), 081106 (Jun 08, 2016) (13 pages) Paper No: FE-15-1323; doi: 10.1115/1.4033416 History: Received May 12, 2015; Revised April 05, 2016

The flow unsteadiness generated in a swirl apparatus is investigated experimentally and numerically. The swirl apparatus has two parts: a swirl generator and a test section. The swirl generator which includes two blade rows, one stationary and one rotating, is designed such that the emanating flow at free runner rotational speed resembles that of a Francis hydroturbine operated at partial discharge. The test section consists of a conical diffuser similar to the draft tube cone of a Francis turbine. Several swirling flow regimes are produced, and the laser Doppler anemometry (LDA) measurements are performed along three survey axes in the test section for different runner rotational speeds (400–920 rpm), with a constant flow rate, 30 l/s. The measured mean velocity components and its fluctuating parts are used to validate the results of unsteady numerical simulations, conducted using the foam-extend-3.0 CFD code. Furthermore, phase-averaged pressure measured at two positions in the draft tube is compared with those of numerical simulations. A dynamic mesh is used together with the sliding general grid interfaces (GGIs) to mimic the effect of the rotating runner. The delayed detached-eddy simulation method, conjugated with the Spalart–Allmaras turbulence model (DDES–SA), is applied to achieve a deep insight about the ability of this advanced modeling technique and the physics of the flow. The RNG kε model is also used to represent state-of-the-art of industrial turbulence modeling. Both models predict the mean velocity reasonably well while DDES–SA presents more realistic flow features at the highest and lowest rotational speeds. The highest level of turbulence occurs at the highest and lowest rotational speeds which DDES–SA is able to predict well in the conical diffuser. The special shape of the blade plays more prominent role at lower rotational speeds and creates coherent structures with opposite sign of vorticity. The vortex rope is captured by both turbulence models while DDES–SA presents more realistic one at higher rotational speeds.

Copyright © 2016 by ASME
Your Session has timed out. Please sign back in to continue.

References

Clausen, P. , Koh, S. , and Wood, D. , 1993, “ Measurements of a Swirling Turbulent Boundary Layer Developing in a Conical Diffuser,” Exp. Therm. Fluid Sci., 6(1), pp. 39–48. [CrossRef]
Dörfler, P. , Sick, M. , and Coutu, A. , 2013, Flow-Induced Pulsation and Vibration in Hydroelectric Machinery, Springer-Verlag, Berlin.
Escudier, M. P. , and Keller, J. , 1985, “ Recirculation in Swirling Flow—A Manifestation of Vortex Breakdown,” AIAA J., 23(1), pp. 111–116. [CrossRef]
Shtern, V. , and Hussain, F. , 1999, “ Collapse, Symmetry, Breaking, and Hysteresis in Swirling Flow,” Annu. Rev. Fluid Mech., 31(1), pp. 537–566. [CrossRef]
Javadi, A. , and Nilsson, H. , 2014, “ A Comparative Study of Scale-Adaptive and Large-Eddy Simulations of Highly Swirling Turbulent Flow Through an Abrupt Expansion,” IOP Conf. Ser.: Earth Environ. Sci., 22, p. 022017.
Javadi, A. , and Nilsson, H. , 2015, “ LES and DES of Strongly Swirling Turbulent Flow Through a Suddenly Expanding Circular Pipe,” Comput. Fluids, 107, pp. 301–313. [CrossRef]
Guo, B. , Langrish, T. , and Fletcher, D. , 2002, “ CFD Simulation of Precession in Sudden Pipe Expansion Flows With Low Inlet Swirl,” Appl. Math. Model, 26(1), pp. 1–15. [CrossRef]
Zohir, A. , Aziz, A. A. , and Habib, M. , 2011, “ Heat Transfer Characteristics in a Sudden Expansion Pipe Equipped With Swirl Generators,” Int. J. Heat Fluid Flow, 32(1), pp. 352–361. [CrossRef]
Robinson, S. , Kline, S. , and Spalart, P. , 1988, “ Quasi-Coherent Structures in the Turbulent Boundary Layer: Part II. Verification and New Information From a Numerically Simulated Flat-Plate Layer,” Zoran Zaric Memorial International Seminar on Near-Wall Turbulence, Dubrovnik, Yugoslavia, May 16–20.
Kim, J. , and Lee, M. , 1991, “ The Structure of Pressure Fluctuations in Turbulent Shear Flows,” Turbulent Shear Flows 7, Springer-Verlag, Berlin, pp. 87–99.
Javadi, A. , Krane, E. , and Nilsson, H. , 2015, “ Exploration of Rotation/Curvature Correction Method in Hydropower Application,” 8th International Symposium on Turbulence Heat and Mass Transfer 8 (THMT15), Sarajevo, Bosnia and Herzegovina, Sept. 15–18.
Gyllenram, W. , and Nilsson, H. , 2008, “ Design and Validation of a Scale-Adaptive Filtering Technique for LRN Turbulence Modeling of Unsteady Flow,” ASME J. Fluids Eng., 130(5), p. 051401. [CrossRef]
Javadi, A. , and Nilsson, H. , 2014, “ LES and DES of Swirling Flow With Rotor–Stator Interaction,” Progress in Hybrid RANS-LES Modeling (Notes on Numerical Fluid Mechanics and Multidisciplinary Design, Vol. 130), Springer International Publishing, Berlin, pp. 457–468.
Spalart, P. , Deck, S. , Shur, M. , Squires, K. , Strelets, M. , and Travin, A. , 2006, “ A New Version of Detached-Eddy Simulation, Resistant to Ambiguous Grid Densities,” Theor. Comput. Fluid Dyn., 20(3), pp. 181–195. [CrossRef]
Spalart, P. , 2009, “ Detached-Eddy Simulation,” Annu. Rev. Fluid Mech., 41(3), pp. 181–202. [CrossRef]
Javadi, A. , and Nilsson, H. , 2015, “ Time-Accurate Numerical Simulations of Swirling Flow With Rotor–Stator Interaction,” Flow, Turbul. Combust., 95(4), pp. 755–774. [CrossRef]
Bosioc, A. , Susan-Resiga, R. , Muntean, S. , and Tănasă, C. , 2012, “ Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone,” ASME J. Fluids Eng., 134(8), p. 081104. [CrossRef]
Susan-Resiga, R. , Muntean, S. , and Bosioc, A. , 2008, “ Blade Design for Swirling Flow Generator,” 4th German–Romanian Workshop on Turbomachinery Hydrodynamics (GROWTH-4), Stuttgart, Germany, June 12–15, pp. 1–16.
Minakov, A. , Platonov, D. , Litvinov, I. , and Hanjalić, K. , 2015, “ Computer Simulation of Flow at Part Load in a Laboratory Model of Kaplan Hydroturbine by RANS, DES and LES,” 8th International Symposium on Turbulence Heat and Mass Transfer 8 (THMT15), Sarajevo, Bosnia and Herzegovina, Sept. 15–18.
Leclaire, B. , and Sipp, D. , 2010, “ A Sensitivity Study of Vortex Breakdown Onset to Upstream Boundary Conditions,” J. Fluid Mech., 645, pp. 81–119. [CrossRef]
Susan-Resiga, R. , Muntean, S. , Bosioc, A. , Stuparu, A. , Miloş, T. , Baya, A. , Bernad, S. , and Anton, L. , 2007, “ Swirling Flow Apparatus and Test Rig for Flow Control in Hydraulic Turbines Discharge Cone,” 2nd International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Timişoara, Romania, Oct. 24–26, pp. 203–217.
Tănasă, C. , Susan-Resiga, R. , Muntean, S. , and Bosioc, A. , 2013, “ Flow-Feedback Method for Mitigating the Vortex Rope in Decelerated Swirling Flows,” ASME J. Fluids Eng., 135(6), p. 061304. [CrossRef]
Muntean, S. , Bosioc, A. , Stanciu, R. , Tănasă, C. , Susan-Resiga, R. , and Vekas, L. , 2011, “ 3D Numerical Analysis of a Swirling Flow Generator,” 4th International Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Belgrade, Serbia, Oct. 26–28, pp. 115–125.
Susan-Resiga, R. , and Muntean, S. , 2009, “ Decelerated Swirling Flow Control in the Discharge Cone of Francis Turbines,” Fluid Machinery and Fluid Mechanics, J. Xu , Y. Wu , Y. Zhang , and J. Zhang , eds., Springer, Berlin, pp. 89–96.
Iliescu, M. , Ciocan, G. , and Avellan, F. , 2008, “ Analysis of the Cavitating Draft Tube Vortex in a Francis Turbine Using Particle Image Velocimetry Measurements in Two-Phase Flow,” ASME J. Fluids Eng., 130(2), p. 021105. [CrossRef]
Bosioc, A. , Muntean, S. , Tănasă, C. , Susan-Resiga, R. , and Vekas, L. , 2014, “ Unsteady Pressure Measurements of Decelerated Swirling Flow in a Draft Tube Cone at Lower Runner Speeds,” IOP Conf. Ser.: Earth Environ. Sci., 22(3), p. 032008. [CrossRef]
Javadi, A. , Bosioc, A. , Nilsson, H. , Muntean, S. , and Susan-Resiga, R. , 2014, “ Velocity and Pressure Fluctuations Induced by the Precessing Helical Vortex in a Conical Diffuser,” IOP Conf. Ser.: Earth Environ. Sci., 22(3), p. 032009. [CrossRef]
Susan-Resiga, R. F. , Muntean, S. , Avellan, F. , and Anton, I. , 2011, “ Mathematical Modelling of Swirling Flow in Hydraulic Turbines for the Full Operating Range,” Appl. Math. Modell., 35(10), pp. 4759–4773. [CrossRef]
van Leer, B. , 1979, “ Towards the Ultimate Conservative Difference Scheme. V. A Second-Order Sequel to Godunov's Method,” J. Comput. Phys., 32(1), pp. 101–136. [CrossRef]
ANSYS, 2013, “ ANSYS ICEM CFD®: Academic Research, Release 15, Help System, Coupled Field Analysis Guide,” ANSYS, Inc., Canonsburg, PA.
Beaudoin, M. , and Jasak, H. , 2008, “ Development of a Generalized Grid Interface for Turbomachinery Simulations With OpenFOAM,” Open source CFD International Conference, Berlin, Germany, Dec. 4–5.
Nilsson, H. , Page, M. , Beaudoin, M. , Gschaider, B. , and Jasak, H. , 2008, “ The OpenFOAM Turbomachinery Working Group, and Conclusions From the Turbomachinery Session of the Third OpenFOAM Workshop,” 24th IAHR Symposium on Hydraulic Machinery and Systems, Foz do Iguassu, Brazil, Oct. 27–31.
Javadi, A. , and Nilsson, H. , 2015, “ Active Flow Control of Vortex Rope in a Conical Diffuser,” IAHR WG Meeting on Cavitation and Dynamic Problems in Hydraulic Machinery and Systems, Ljubljana, Slovenia, Sept. 9–11, pp. 99–106.
Komerath, N. , Hegde, U. , and Strahle, W. , 1985, “ Turbulent Static Pressure Fluctuations Away From Flow Boundaries,” AIAA J., 23(9), pp. 1320–1326. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

(a) Schematic view of experimental closed-loop test rig and (b) schematic view of swirl generator

Grahic Jump Location
Fig. 2

Sketch of the test section with survey axes W0, W1, and W2. Two wall pressure taps in draft tube: PT1 at throat and PT2 100 mm axially downstream of first tap.

Grahic Jump Location
Fig. 3

Characteristic m(q) dependence for the swirl apparatus

Grahic Jump Location
Fig. 4

(a) Swirl generator delivers swirling flows similar to Francis turbine and (b) mesh configuration used by DDES–SA computations

Grahic Jump Location
Fig. 5

Axial, W, and tangential, U, mean velocity compared with experimental results for 400 rpm: (a) W0, 400 rpm, (b) W1, 400 rpm, and (c) W2, 400 rpm. Solid line: DDES–SA, solid line with ×: RNG k−ε, and markers: experimental results.

Grahic Jump Location
Fig. 6

Axial, W, and tangential, U, mean velocity compared with experimental results for 600 rpm: (a) W0, 600 rpm, (b) W1, 600 rpm, and (c) W2, 600 rpm. Solid line: DDES–SA, solid line with ×: RNG k−ε, and markers: experimental results.

Grahic Jump Location
Fig. 7

Axial, W, and tangential, U, mean velocity compared with experimental results for 920 rpm: (a) W0, 920 rpm, (b) W1, 920 rpm, and (c) W2, 920 rpm. Solid line: DDES–SA, solid line with ×: RNG k−ε, and markers: experimental results.

Grahic Jump Location
Fig. 8

Axial, wrms′, and tangential, urms′, velocity fluctuation RMS: (a) W0, 400 rpm, (b) W0, 600 rpm, (c) W0, 920 rpm, (d) W1, 400 rpm, (e) W1, 600 rpm, and (f) W1, 920 rpm. Circle line: experimental tangential, star line: experimental axial, dash: DDES–SA tangential, and solid line: DDES–SA axial.

Grahic Jump Location
Fig. 9

Pressure fluctuation RMS by DDES–SA, p*=prms′/ρWthroat2: (a) W0 and (b) W1. Dashed dotted: 920 rpm, solid line: 400 rpm, and × line: 600 rpm.

Grahic Jump Location
Fig. 10

Axial vorticity at two cross sections in the runner by DDES–SA (close to the leading and trailing edges): (a) 400 rpm, (b) 600 rpm, and (c) 920 rpm. α: hub effect, β: shroud effect, γ: separation at suction side, and ζ: interaction of shroud effect and the blade wake. The arrow shows how the shroud effect intensifies in the runner.

Grahic Jump Location
Fig. 11

Phase-averaged pressure at 920 rpm from PT1 and PT2 in the draft tube compared with numerical results. Three profiles of PT1 are shifted 0.01 vertical unit downward for clarity.

Grahic Jump Location
Fig. 12

Isosurface of pressure by ((a) 400 rpm, (c) 600 rpm, and (e) 920 rpm) RNG k−ε and ((b) 400 rpm, (d) 600 rpm, and (f) 920 rpm) DDES–SA

Grahic Jump Location
Fig. 13

Temporal power spectral density (PSD) versus normalized frequency for a probe at the on-axis point of W1 captured by LDA: ((a)–(c)) tangential (U-component velocity PSD) velocity component: 400 rpm, 600 rpm, and 920 rpm; ((d)–(f)) axial (W-component velocity PSD) velocity component: 400 rpm, 600 rpm, and 920 rpm

Grahic Jump Location
Fig. 14

Temporal PSD of axial (W-component velocity PSD) and tangential (U-component velocity PSD) velocity components versus normalized frequency for a probe at the on-axis point of W1 using DDES–SA. Straight line is Kolmogorov −5/3 slope: (a) 400 rpm, (b) 600 rpm, and (c) 920 rpm. U-component velocity PSD is shifted 100 units downward for clarity.

Grahic Jump Location
Fig. 15

Vorticity magnitude at three cross sections in the draft tube by DDES–SA: (a) 400 rpm, (b) 600 rpm, and (c) 920 rpm

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In