Numerical investigation of three-dimensional flow around a free-spanned pipeline

Three-dimensional flow around a free-spanned pipeline is simulated using a fractional step finite element method. The Reynolds number, based on the pipe-diameter and the approaching flow velocity, is set at 500 and 5 x 10(5) to simulate both laminar and turbulent flow; In high Reynolds number case, Smagorinsky SGS closure is used to model the turbulent flow. It was found, from the limited amount of numerical data, that a spiral vortex tube is formed around the span shoulder and extends around the span shoulder, which is quite similar to the assumption made by Sumer and Fredsoe. It is also found that there are significant shear stress concentrations in the span shoulder area. The reasons for the shear stress concentration are discussed.