Wind and Structures

  • 제12권1호
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  • Pages.49-61
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  • 2009
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  • 1226-6116(pISSN)
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  • 1598-6225(eISSN)
테크노프레스 (Techno-Press)
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Effect of blockage on the drag of a triangular cylinder

  • Yeung, W.W.H. (School of Mechanical and Aerospace Engineering, Nanyang Technological University)
  • 투고 : 2008.09.01
  • 심사 : 2008.12.09
  • 발행 : 2009.01.25
⟨ 이전 논문 다음 논문 ⟩

초록

A method is presented to estimate the form drag and the base pressure on a triangular cylinder in the presence of blockage effect. The Strouhal number, which is found to increase with the flow constriction experimentally by Ramamurthy & Ng (1973), may be decoupled from the blockage effect when re-defined by using the velocity at flow separation and a theoretical wake width. By incorporating this wake width into the momentum equation by Maskell (1963) for the confined flow, a relationship between the form drag and the base pressure is derived. Independently, the experimental data of surface pressure from Ramamurthy & Lee (1973) are found to be independent of the blockage effect when expressed in terms of a modified pressure coefficient involving the pressure at separation. Using the potential flow model by Parkinson & Jandali (1970) and its subsequent development in Yeung & Parkinson (2000) for the unconfined flow, a linear relation between the pressure at separation and the form drag is formulated. By solving the two equations simultaneously with a specified blockage ratio and an apex angle of the triangular cylinder, the predictions of the drag and the base pressure are in reasonable agreement with experimental data. A new theoretical relationship for the Strouhal number, pressure drag coefficient and base pressure proposed in this study allows the confinement effect to be appropriately taken into consideration. The present approach may be extended to three-dimensional bluff bodies.

키워드

참고문헌

  1. Allen, H.J. and Vincenti, W.G. (1944), "Wall interference in a two-dimensional-flow wind tunnel, with consideration of the effect of compressibility", NACA Report 782.
  2. Barlow, J.B., Rae, W.H. and Pope, A. (1999), Low-speed Wind Tunnel Testing, 3rd edition, Wiley-Interscience.
  3. Bearman, P. W. (1967), "On the vortex street wakes", J. Fluid Mech., 28, 625-641. https://doi.org/10.1017/S0022112067002368
  4. Chen, Y.S. (1967), "Effect of confining walls on the periodic wake of 90-degree wedges", Master's thesis, University of Iowa. (See Richter, A. and Naudascher, E. (1976))
  5. Cigada, Malavasi and Vanali, M. (2006), "Effects of an asymmetrical confined flow on a rectangular cylinder", J. Fluids Struct., 22, 213-227. https://doi.org/10.1016/j.jfluidstructs.2005.09.006
  6. Csiba, A.L. and Martinuzzi, R.J. (2008), "Investigation of bluff body asymmetry on the properties of vortex shedding", J. Wind Eng. Ind. Aerod., 96, 1152-1163. https://doi.org/10.1016/j.jweia.2007.06.037
  7. El-Sherbiny, S. (1980), "Side walls in constrained flow", Proc. 4th Colloq. Industrial Aerodynamics, Fachhochschule Aachen, Germany.
  8. Griffin, O.M. (1981), "Universal similarity in the wakes of stationary and vibrating bluff structures", Trans. ASME, J. Fluids Eng., 103, 52-58. https://doi.org/10.1115/1.3240780
  9. Holmes, J.D. (2007), Wind loading of structures, 2nd edition, Taylor & Francis.
  10. Kong, L., Hameury, M. and Parkinson, G.V. (1998), "Unsteady-flow testing in a low-correction wind tunnel", J. Fluids Struct., 12, 33-45. https://doi.org/10.1006/jfls.1997.0126
  11. Lasher, W.C. (2001), "Computation of two-dimensional blocked flow normal to a flat plate", J. Wind Eng. Ind. Aerod., 89, 493-513. https://doi.org/10.1016/S0167-6105(00)00076-3
  12. Maskell, E.C. (1963), "Theory of the blockage effects on bluff bodies and stalled wings in a closed wind tunnel", Aeronautical Research Council, Report and Memorandum 3400.
  13. Meyer, O. and Nitsche, W. (2004), "Update on progress in adaptive wind tunnel wall technology", Progress in Aerospace Sciences, 40, 2004, 119-141. https://doi.org/10.1016/j.paerosci.2004.02.001
  14. Modi, V.J. and El-Sherbiny, S.E. (1977), "A free-streamline model for bluff bodies in confined flow", Trans. ASME, J. Fluids Eng., 99, 585-592. https://doi.org/10.1115/1.3448854
  15. Naudascher, E. (1991), Hydrodynamic forces, Taylor & Francis.
  16. Ota, T., Okamoto, Y. and Yoshikawa, H. (1994), "A correction formula for wall effects on unsteady forces of two-dimensional bluff bodies", Trans. ASME, J. Fluids Eng., 116, 414-418. https://doi.org/10.1115/1.2910292
  17. Parkinson, G.V. and Jandali, T. (1970), "A wake source model for bluff body potential flow", J. Fluid Mech., 40, 577-594. https://doi.org/10.1017/S0022112070000320
  18. Parkinson, G.V. (1984), "A tolerant wind tunnel for industrial aerodynamics", J. Wind Eng. Ind. Aerod., 16, 293-300. https://doi.org/10.1016/0167-6105(84)90012-6
  19. Parkinson, G.V. and Hameury, M. (1990), "Performance of the tolerant tunnel for bluff body testing", J. Wind Eng. Ind. Aerod., 33, 35-42. https://doi.org/10.1016/0167-6105(90)90018-8
  20. Ramamurthy, A.S. and Lee, P.M. (1973), "Wall effects on flow past bluff bodies", J. Sound Vib., 31(4), 443-451. https://doi.org/10.1016/S0022-460X(73)80259-7
  21. Ramamurthy, A.S. and Ng, C.P. (1973), "Effects of blockage on steady force coefficients", J. Eng. Mech., Div. ASCE, 99, 755-772.
  22. Ramamurthy, A.S., Balachandar, R. and Vo, D.N. (1989), "Blockage correction for sharp-edged bluff bodies", J. Eng. Mech., Div. ASCE, 115, 1569-1576. https://doi.org/10.1061/(ASCE)0733-9399(1989)115:7(1569)
  23. Ranga Raju, K.G. and Garde, R.J. (1970), "Resistance of an inclined plate placed on a plane boundary in twodimensional flow", Trans. ASME, J. Basic Eng., 92, 21-28. https://doi.org/10.1115/1.3424938
  24. Rehimi, F., Aloui, F., Nasrallah, S.B., Doubliez, L. and Legrand, J. (2008), "Experimental investigation of a confined flow downstream of a circular cylinder centred between two parallel walls", J. Fluids Struct., 24, 855-882. https://doi.org/10.1016/j.jfluidstructs.2007.12.011
  25. Richter, A. and Naudascher, E. (1976), "Fluctuating forces on a rigid circular cylinder in confined flow", J. Fluids Mech., 78, 561-576. https://doi.org/10.1017/S0022112076002607
  26. Roshko, A. (1954), "On the drag and shedding frequency of two-dimensional bluff bodies", NACA report 3169.
  27. Sahin, M. and Owens, R.G. (2004), "A numerical investigation of wall effects up to high blockage ratios on twodimensional flow past a confined circular cylinder", Phys. Fluids, 16, 1305-1320. https://doi.org/10.1063/1.1668285
  28. Simmons, J.E.L. (1975), "Effect of separation angle on vortex streets", J. Eng. Mech., 101, 649-661.
  29. Sumner, D. and Brundrett, E. (1995), "Testing three-dimensional bluff-body models in a low-speed twodimensional adaptive wall test section", Trans. ASME, J. Fluids Eng., 117, 546-551. https://doi.org/10.1115/1.2817299
  30. Toebes, G.H. (1971), "The frequency of oscillatory forces acting on bluff cylinders in constricted passages", Proc. of 14th Congress of International Hydraulic Research, Paris, France, 2(B-7), 58. (See Ramamurthy, A.S. and Ng, C.P. (1973))
  31. Twigg-Molecey, C.F.M. and Baines, W.D. (1973), "Aerodynamics forces on a triangular cylinder", J. Eng. Mech., Div. ASCE, 99, 803-818.
  32. Yeung, W.W.H. and Parkinson, G.V. (2000), "Base pressure prediction in bluff-body potential-flow models", J. Fluids Mech., 423, 381-394. https://doi.org/10.1017/S0022112000002044
  33. Yeung, W.W.H. (2008), "Self-similarity of confined flow past a bluff body", J. Wind Eng. Ind. Aerod., 96, 369-388. https://doi.org/10.1016/j.jweia.2007.10.001