Minimizing Transverse Flow Effects on Passing Ships at Inland Waterways

Transverse flows from lateral water discharges, e. g. from cooling water outlets at power stations or storm water outfalls, into inland waterways (rivers and canals) may affect passing ships. To provide operational traffic safety such transverse flow effects on ships from outfall structures are to be restricted with suitable cross-flow velocities and cross-flow distributions. Inland canals in Germany allow operation of ships with lengths up to 185 m and widths up to 11.4 m, were dimensions are restricted by locks. Allowing a traffic lane width of 16 m in each direction, there is a safety clearance of 2 m between the lanes. Ship speeds may not exceed 12 km/h for low draft ships and 8 km/h for deep draft ships. Ships approaching locks reduce speed and thus loose manoeuverability. Drifts on ships passing outfall structures depend on ship parameters, parameters of fairway, and parameters of lateral water discharge. For a storm water outfall in the City of Bamberg (Germany) with strong topographic restrictions at the Main-Danube-Canal in the approach to a lock, drifts on ships passing the lateral discharge location shall not to exceed a safety clearence of 2 m between the traffic lanes for extremely low ship speeds of 3 km/h. Following a prelimilary empirical approach extensive physical model tests, scale 1:25, with prototype ships passing the outfall structure have been performed and compared with 3-D numerical simulations using Computational Fluid Dynamics (CFD) Technique. With a uniform flow distribution obtained with an overflow weir and a submerged wall, ship drifts were acceptable for varying discharges.