Experimental Investigation of the Hydrodynamic Behavior of a Flexible Line of Floating Modules to Contain Wood Logs Upstream of Hydroelectric Plants

The containment of wood logs and debris floating in the river upstream of Brazil’s Santo Antônio hydroelectric plant is a major issue for the plant’s operation. Log booms are floating structures assembled in the shape of a long chain to divert heavy wood logs from the machinery. The present study proposes a method to evaluate the overall hydrodynamic loads acting on a log-boom line based on experiments with scale modules in a towing tank and analytical models of the line. Experiments with a single module and a set of three log-boom modules were performed to determine the hydrodynamic drag, lift, and moment acting on the modules as a function of the yaw angle for low Froude numbers. These coefficients were employed in analytical models to calculate the shape of the line and the overall loads. The first model assumed a catenary-like geometry of the line, whereas the second assumed a parabolic geometry. The results were evaluated for two lines with five and seven log booms towed in the tank. A good agreement of load results was observed for the tested Froude number range, indicating that the method may be employed to design river floating barriers.