Abstract:

ESDU 80025 provides data for estimating the mean forces and pressures induced by flow normal or inclined to a cylindrical structure of circular cross-section. The data apply when the effect of the flow around the free end (or ends) can be ignored (i.e. for two-dimensional flow). ESDU 81017 provides additional information in the form of correction factors that can be applied to these data to account for end effects and shear flow effects, such as those associated with cantilever structures in the non-uniform atmospheric wind. Drag coefficients are given as a function of Reynolds number (10E-2 to 10E7), the turbulence properties of the oncoming flow and surface roughness for which guidance is given on typical values. The effects of spanwise protrusions and other nearby plane surfaces are quantified as are the effects of perforations and helical strakes. Data are provided, in equation form, giving both mean and fluctuating surface pressure distributions and the mean velocity flow field for cylinders with a smooth or rough surface at Reynolds numbers between about 10E5 and 10E7. Calculation sheets are provided to summarise the step-by-step estimation procedures.