Basic bluff-body aerodynamics - Wind Loading of Structures - page 112

from Equation (4.24).
Then from Equation (4.30),
(4.31)
Thus, the mean-square total fluctuating force is directly proportional to the correlation
length, ℓ This is an important result that is applicable to structures such as slender towers.
4.7 Summary
This chapter has attempted to summarize the relevant aspects of bluff-body
aerodynamics, itself a large subject with applications in many fields, to wind loads on
structures. The basic fluid mechanics of stagnation, separation and wakes has been
described, and pressure and force coefficients are defined. The characteristics of
pressures and forces on the basic shapes of flat plates and walls, cubes and rectangular
prisms and circular cylinders have been described. The effect of turbulence and the
ground surface are covered.
Fluctuating pressures and forces, particularly those generated by upwind turbulence,
and the regular shedding of vortices by a bluff body are discussed. The concept of
correlation length and the averaging process by which fluctuating total forces on a body
can be calculated are described.
References
Baines, W.D. (1963) Effects of velocity distributions on wind loads and flow patterns on buildings.
Proceedings, International Conference on Wind Effects on Buildings and Structures,
Teddington UK, 26-28 June, pp. 198-225.
Bearman, P.W. (1971) An investigation of the forces on flat plates normal to a turbulent flow.
Journal of Fluid Mechanics, 46:177-98.
Bearman, P.W. and Trueman, D.H. (1972) An investigation of the flow around rectangular
cylinders. Aeronautical Quarterly, 23:229-37.
Chen, J.M. and Fang, Y.-C. (1996) Strouhal numbers of inclined flat plates. Journal of Wind
Engineering & Industrial Aerodynamics, 61:99-102.
Cook, N.J. (1990) The Designer's Guide to Wind Loading of Building Structures. Part 2 Static
Structures. Building Research Establishment and Butterworths, London.
ESDU (1970) Fluid forces and moments on flat plates. Engineering Sciences Data Unit (ESDU
International, London). ESDU data item 70015.
ESDU (1980) Mean forces, pressures and flow field velocities for circular cylindrical structures:
single cylinder with two-dimensional flow. Engineering Sciences Data Unit (ESDU
International, London). ESDU data item 80025.
Gartshore, I.S. (1973) The effects of freestream turbulence on the drag of rectangular two-
dimensional prisms. Boundary Layer Wind Tunnel Report, BLWT-4-73, University of Western
Ontario.
Jensen, M. (1958) The model law for phenomena in the natural wind. Ingenioren, 2:121-8.