Engineers are often required to design structural nodes at which several tubulars meet. An understanding of the fluid mechanics in the vicinity of a node is necessary in cases where the node is subjected to wind, current or wave loads. This paper describes two series of experiments conducted in order to assess near wake influences on the fluid loading experienced by a typical K-node immersed in unidirectional steady flow. The first series of tests examined the velocity distribution and vortex shedding pattern in the wake of the K-node placed in steady flow in a wind tunnel. The second series consisted of force measurements from the K-node. Velocity and force spectra are presented along with turbulence intensity data.
Many structures, such as fixed steel jacket offshore platforms, are space frames consisting of cylindrical members linked together at nodes. Although a substantial body of information is available to designers concerning fluid loading on isolated cylinders in unidirectional currents and oscillatory flows, very little work has been published on flow past multiple cylinders or nodes where blockage and wake interference effects arise from the close proximity of adjacent members. Given that there are a very large number of nodal configurations possible, this paper will concentrate on unidirectional steady flow past a K-node comprising a vertical primary tubular and two bracing tubulars at 45 0 angles to the vertical. The ratio of diameters between the primary and bracing tubulars is 2:1. Turning to related studies, several investigators have studied interference effects between two cylinders in proximity. Comprehensive reviews on steady flow past parallel cylinders have been produced by Zdravkovich [1,2,3) who observed that cylinder spacing played a crucial role in the magnitude of the total forces experienced by the cylinders whether side by side or in tandem.
