Vortex shedding and drag force reduction

Smoothly curved protuberances (8, 26, 34) are added to an elongate body (2, 16, 18, 20, 22, 32) to modify the fluid flow to reduce the drag Force F_drag and the forces induced by vortex shedding F_vortex. The protuberances can be arranged in diametrically opposed pairs with longitudinally adjacent pairs having different radial directions first to cope with fluid flow from a variety of different directions.