Wind and Structures

  • 제7권5호
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  • Pages.317-332
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  • 2004
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  • 1226-6116(pISSN)
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  • 1598-6225(eISSN)
테크노프레스 (Techno-Press)
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Unsteady 2-D flow field characteristics for perforated plates with a splitter

  • Yaragal, Subhash C. (Department of Civil Engineering, National Institute of Technology Karnataka)
  • 투고 : 2003.11.15
  • 심사 : 2004.06.25
  • 발행 : 2004.10.25
⟨ 이전 논문 다음 논문 ⟩

초록

Wind tunnel experiments were conducted under highly turbulent and disturbed flow conditions over a solid/perforated plate with a long splitter plate in its plane of symmetry. The effect of varied level of perforation of the normal plate on fluctuating velocities and fluctuating pressures measured across and along the separation bubble was studied. The different perforation levels of the normal plate; that is 0%, 10%, 20%, 30%, 40% and 50% are studied. The Reynolds number based on step height was varied from $4{\times}10^3$ to $1.2{\times}10^4$. The shape and size of the bubble vary with different perforation level of the normal plate that is to say the bubble is reduced both in height and length up to 30% perforation level. For higher perforation of the normal plate, bubble is completely swept out. The peak turbulence value occurs around 0.7 to 0.8 times the reattachment length. The turbulence intensity values are highest for the case of solid normal plate (bleed air is absent) and are lowest for the case of 50% perforation of the normal plate (bleed air is maximum in the present study). From the analysis of data it is observed that $\sqrt{\overline{u^{{\prime}2}}}/(\sqrt{\overline{u^{{\prime}2}}})_{max}$, (the ratio of RMS velocity fluctuation to maximum RMS velocity fluctuation), is uniquely related with dimensionless distance y/Y', (the ratio of distance normal to splitter plate to the distance where RMS velocity fluctuation is half its maximum value) for all the perforated normal plates. It is interesting to note that for 50% perforation of the normal plate, the RMS pressure fluctuation in the flow field gets reduced to around 60% as compared to that for solid normal plate. Analysis of the results show that the ratio [$C^{\prime}_p$ max/$-C_{pb}(1-{\eta})$], where $C^{\prime}_p$ max is the maximum coefficient of fluctuating pressure, $C_{pb}$ is the coefficient of base pressure and ${\eta}$ is the perforation level (ratio of open to total area), for surface RMS pressure fluctuation levels seems to be constant and has value of about 0.22. Similar analysis show that the ratio $[C^{\prime}_p$ max/$-C_{pb}(1-{\eta})]$ for flow field RMS pressure fluctuation levels seems to be constant and has a value of about 0.32.

키워드

참고문헌

  1. Arndt, R.E.A. and Nilsen, A.W. (1971), "On the measurement of fluctuating pressure in the mixing zone of a round jet", Fluid Engineering Division, ASME, Paper no. 71-FE-31.
  2. Castro, I.P. and Haque, A. (1987), "The structure of a turbulent shear layer bounding a separation region", J. Fluid Mech., 179, 439-468. https://doi.org/10.1017/S0022112087001605
  3. Cherry, N.J., Hillier, R. and Latour, M.E.M.P. (1984), "Unsteady measurements in a separated and reattaching flow", J. Fluid Mech., 144, 13-46. https://doi.org/10.1017/S002211208400149X
  4. Eaton, J.K. and Johnston, J.P. (1981), "A review of research on subsonic turbulent flow reattachment", AIAA Journal, 19, 1093-1100. https://doi.org/10.2514/3.60048
  5. George, W.K., Benther, P.D. and Arndt, R.E.A. (1984), "Pressure spectra in turbulent free shear flows", J. Fluid Mech., 148, 155-191. https://doi.org/10.1017/S0022112084002299
  6. Govinda Ram, H.S. and Arakeri, V.H. (1990), "Studies on unsteady pressure fields in the region of separating and reattaching flows", J. Fluids Eng., 112, 402-408. https://doi.org/10.1115/1.2909417
  7. Gupta, V.P. and Ranga Raju, K.G. (1987), "Separated flow in lee of solid and porous fences", J. Hyd. Eng., 113, 1264-1276. https://doi.org/10.1061/(ASCE)0733-9429(1987)113:10(1264)
  8. Jenkins, R.C. (1987), "Effects on pitot shape on measurement of flow turbulence", AIAA J. 25, 889-892. https://doi.org/10.2514/3.9719
  9. Kiya, M. and Sasaki, K. (1983), "Structure of turbulent separation bubble", J. Fluid Mech., 137, 83-113. https://doi.org/10.1017/S002211208300230X
  10. Kiya, M. and Sasaki, K. (1985), "Structure of large scale vortices and unsteady reverse flow in the reattaching zone of a turbulent separation bubble", J. Fluid Mech., 154, 463-491. https://doi.org/10.1017/S0022112085001628
  11. Kraichnan, R. (1956), "Pressure field within homogeneous anisotropic turbulence", J. Acoust. Soc. of America, 28(1), 64-72. https://doi.org/10.1121/1.1908224
  12. Mabey, D.G. (1972), "Analysis and correlation of data on pressure fluctuations in separated flow", J. Aircraft, 9(9), 642-645. https://doi.org/10.2514/3.59053
  13. Roshko, A. and Lau, J.C. (1965), "Some observations on transition and reattachment of a free shear layer in incompressible flow", Proc. Heat Transfer, Fluid Mech. Institute., 18, 157-167.
  14. Ruderich. R. and Fernholz, H.H. (1986), "An experimental investigation of a turbulent shear flow with separation, reverse flow, and reattachment", J. Fluid Mech., 163, 283-322. https://doi.org/10.1017/S0022112086002306
  15. Suzuki,Y. and Kiya, M. (1985), "Effect of free stream turbulence on separated reattching flows for different angles of separation", Bulletin of JSME., 28(243), 1887-1892. https://doi.org/10.1299/jsme1958.28.1887
  16. Tsai, G.L. and Yang, J.T. (1993), "Pressure fluctuation in correlation with velocity fluctuations in turbulent wake flow", J. Fluids Eng., 462-463.
  17. Willmarth, W.W. (1975), "Pressure fluctuations beneath a turbulent boundary layer", Ann. Rev. Fluid Mech., 7, 13-38. https://doi.org/10.1146/annurev.fl.07.010175.000305

피인용 문헌

  1. Wind loads for high-solidity open-frame structures vol.14, pp.1, 2011, https://doi.org/10.12989/was.2011.14.1.001