Abstract
The decay of a far wake and its turbulent fluctuations behind two thin discs of the same diameter D, oriented normal to the incident flow, have been studied using the Particle Image Velocimetry (PIV). The experimental study was carried out in a water flume (Re ≈ 2·105) with varying distances between the discs (L х = 4–8D) and their axes shift relative to each other (0, 0.5D and 1D). It is found that the velocity deficit behind two discs depends weakly on L x , and at L х > 40D, it becomes indistinguishable from the level of turbulent fluctuations of the incident flow. It is found that the decay of the average velocity deficit and its turbulent fluctuations in a wake of a tandem of discs can be described by the same analytical dependence with exponent–2/3 as for the wake decay of a single disc. However, at the same distance downstream, the value of deficit behind two discs is substantially higher than the corresponding value behind a single disc. Velocity fluctuations in a far wake behind a pair of discs depend weakly on longitudinal dimension L x , but at the same time, in contrast to the velocity deficit, their level does not differ significantly from the level of fluctuations behind a single disc.
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References
M.M. Zdravkovich, Review of flow interference between two circular cylinders in various arrangements, Trans. ASME. J. Fluids Engng, 1977, Vol. 99, No. 4, P. 618–633.
F. Auteri, M. Belan, G. Gibertini, and D. Grassi, Normal flat plates in tandem: An experimental investigation, J. Wind Engng Ind. Aerodyn., 2008, Vol. 6, No. 96, P. 872–879.
H. Hacışevki and A. Teimourian, Comparison of flow structures in the wake region of two similar normal flat plates in tandem and a square cylinder, Exp. Therm. Fluid Sci., 2015, Vol. 69, P. 169–177.
F. Porté-Agel, Y.T. Wu, and C.H. Chen, Numerical study of the effects of wind direction on turbine wakes and power losses in a large wind farm, Energies, 2013, Vol. 6, No. 10, P. 5297–5313.
X. Yang, S. Kang, and F. Sotiropoulos, Computational study and modeling of turbine spacing effects in infinite aligned wind farms, Physics of Fluids, 2012, Vol. 24, No. 11, P. 115107–1–115107-28.
S. Aubrun, S. Loyera, P.E. Hancock, and P. Hayden, Wind turbine wake properties: Comparison between a nonrotating simplified wind turbine model and a rotating model, J. Wind Engng Ind. Aerodyn., 2013, Vol. 120, P. 1–8.
A. Roshko, On the wake and drag of bluff bodies, J. Aeronautical Sci., 1955, Vol. 2, P. 124–132.
J. Yang, M. Liu, G. Wu, W. Zhong, and X. Zhang, Numerical study on coherent structure behind a circular disk, J. Fluids Struct., 2014, Vol. 51, P. 172–188.
B.G. Novikov, Effect of small total pulse on development of a wake behind the self-propelled bodies, Thermophysics and Aeromechanics, 2009, Vol. 16, No. 4, P. 561–583.
P.B. Johansson, W.K. George, and M.J. Gourlay, Equilibrium similarity, effects of initial conditions and local Reynolds number on the axisymmetric wake, Phys. Fluids, 2003, Vol. 15, No. 3, P. 603–617.
P.B. Johansson and W.K. George, The far downstream evolution of the high-Reynolds number axisymmetric wake behind a disk. Part 1. Single-point statistics, J. Fluid Mech., 2006, Vol. 555, P. 363–385.
I.V. Naumov, I.V. Litvinov, R.F. Mikkelsen, and V.L. Okulov, Investigation of a wake decay behind a circular disc in a hydro channel at high Reynolds numbers, Thermophysics and Aeromechanics, 2015, Vol. 22, No. 6, P. 657–665.
Y.N. Nakamura, Vortex shedding from bluff bodies and a universal Strouhal number, J. Fluids Struct., 1996, Vol. 10, P. 159–171.
J.P. Bentley and A.R. Nichols, The mapping of vortex fields around single and dual bluff bodies, Flow Meas. Instrum., 1990, Vol. 1, P. 278–286.
V.L. Okulov, I.V. Naumov, R.F. Mikkelsen, I.K. Kabardin, and J.N. Sørensen, A regular Strouhal number for large-scale instability in the far wake of a rotor, J. Fluid Mech., 2014, Vol. 747, P. 369–380.
I.V. Naumov, V.V. Rahmanov, V.L. Okulov, K.M. Velte, K.E. Mayer, and R.F. Mikkelsen, Flow diagnostics downstream of a tribladed rotor model, Thermophysics and Aeromechanics, 2012, Vol. 19, No. 2, P. 171–181.
I.V. Naumov, R.F. Mikkelsen, V.L. Okulov, and J.N. Sørensen, PIV and LDA measurements of the wake behind a wind turbine model, J. Phys.: Conference Series, 2014, Vol. 524, No. 1, P. 12168–12177.
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Research is financially supported by the Russian Foundation for Basic research grant (Project No. 14-29-00093).
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Naumov, I.V., Litvinov, I.V., Mikkelsen, R.F. et al. Experimental investigation of wake evolution behind a couple of flat discs in a hydrochannel. Thermophys. Aeromech. 23, 657–666 (2016). https://doi.org/10.1134/S0869864316050048
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DOI: https://doi.org/10.1134/S0869864316050048