Safe Navigation Speeds and Clearance at Lower Sill, Temporary Lock 52, Ohio River

摘要

This investigation has identified four possible mechanisms for producing tow squat, the vertical drop of the tow due to motion, measured from the still water level, in the temporary lock at Locks and Dam 52. Based on tests with tows either self-propelled or pulled with a towing apparatus, this investigation shows that squat for entering tows is determined by different parameters from those for exiting tows. The maximum squat for almost every self-propelled test (entering or exiting) was located at the stern of the towboat. For loaded tows entering the lock, the primary mechanism producing squat was propeller squat. Because tests involving entering tows using the towing apparatus produced very little squat for entering tows. For loaded tows exiting the lock, propeller squat is still an important mechanism for producing sqat. This importance was illustrated by the acceleration tests, during which all the tows approached the sill at the same speed. Squat increased for increased propeller speed. The towing tests show tow speed to be another significant factor in defining squat for existing loaded tows. It was not determined whether this squat was displacement or piston squat. Unloaded exiting tows also have the potential for enough squat to strike the lower sill when operating at high propeller and potential for enough squat to strike the lower sill when operating at high propeller and tow speed. It is likely that displacement, propeller, and moment squat all contribute to the total squat for unloaded exiting tows. The downstream gates for the emptying flume should remain open during tow entry/exit. Entry/exit speeds were higher with the values open. For equal tow speeds, squat is considerably less with the valves open.