Fluid dynamics around an inclined cylinder with running water rivulets

The formation of water rivulets running along an inclined circular cylinder and its effects on the near-wake were experimentally investigated. Water was released from the upper end of the cylinder at a volume flow rate Q. At an incoming wind speed U∞=8-15m/s, two water rivulets were observed near the flow separation points, running along the cylinder inclined at α=45° for 0°⩽β⩽90°, where β is the cylinder yaw angle, and both oscillating circumferentially. The dependence of the rivulet formation on U∞, Q and β is examined in detail. The quasi-periodic vortex street is observed intermittently with and without the presence of the rivulets. The rivulets cause an increase in the normalized dominant frequencies in the near wake and further lead to a significant increase in the drag coefficient, which is consistent with the violent vibration associated with the rain-wind-structure interactions. The effect of the rivulets on the near-wake vortices is investigated. It is found that the vortex strength grows by up to 60% as β increases from 0° to 30°. A mechanism for the rain-wind-induced cable vibration is proposed.