Calculation method of estimating wind forces is studied using the concept of vortex shedding. The general theory based on a Fredholm type integral equation of the 2nd kind is introduced into the problem, in which the unknowns of both vortex and source distributions on the body surface are signified simultaneously, and this problem leads to the so-called well-posed problem differing from the usual Discrete Vortex Method. Furthermore, another calculation method of the pressure distribution on the body surface is proposed considering with the unsteadiness of vortex shedding. Numerical examples are shown for simple cases to confirm validity of this method.
Wind tunnel experiment still remains to be indispensable for estimating wind forces acting on certain structures such as tall buildings and long bridges etc., since the air flow behind the structure is accompanied by flow separation which leads to a complicated problem different from usual lifting problem. In recent years, four typical computational methods such as Finite Element Method (FEM)(Shimura et al.,1988; Donea et al., 1982), Boundary Element Method (BEM)(Hasegawa et a1.,1986;Tosaka et a1.,1987), Finite Difference Method(FDM) (Kawamura et al.,1984; OkaJima,1988) and Discrete Vortex Method(DVM) (Inamuro et al.,1986; KawaI,1988) for wind-force analysis, have become much familiar with the advent of high performance computer. DVM is generally appreciated in this field because of its simplicity in theoretical structure, comparing with the others and is appraised its applicability in high Reynolds-number region in deciding the separation point from the body surface. However, there still exist certain problems in the ordinary DVM, such that the fundamental equation for the unknowns of vortex strength on body surface is a Fredholm type integral equation of the 1st kind which leads to an ill-posed problem (Hayakawa,1992), and that the number of the unknowns does not coincide with that of necessary boundary conditions.
