Safety Grates in Supercritical Channels

Abstract

In areas of steep terrain, concrete lined channels designed for supercritical flow are often used to convey stormwaters. During dry conditions, concrete channels attract playing animals, children, and adults. These channels are hazardous during storms because of the high water velocities. Even more hazardous, a trash rack placed in the channel has the potential to pin a person to the rack, preventing escape from the waters. A parabolic shaped grate designed to deliver victims to safety is modeled. Results show that the grate can be appropriate for supercritical flow channels. The parabolic shape works with the velocity profile of the water by providing a flatter slope as the velocity of the flow increases. Floating objects sweep up the grate out of the flow of the water. A severe clogging factor has little effect on the grate. If the channel is designed with a hydraulic jump induced on the grate, the jump can aid in pushing a victim up the grate.