A Comparison of Formed Suction Inlets for Flood Control Applications

Formed suction inlets (FSI) are commonly used with large vertical pumps in flood control applications. The US Army Corps of Engineers Type 10 FSI is used extensively throughout the southeastern United States. However, variations of this inlet have been utilized with increasing frequency for a variety of reasons including cost, flexibility of use in existing intakes and smaller foot prints. Type 10 formed suction inlets have a proven record of success in a wide variety of approach flow conditions including high cross flow applications and with less than ideal vertical or horizontal transitions. Published guidelines and extensive field experience provide reliable design guidance for this type of inlet. While design guidance has been published on alternative inlets there is very little information or data available providing a direct comparison of effectiveness between a Type 10 with an alternative FSI. This paper presents the results of a physical model study which was conducted with the specific goal of comparing the Army Corps of Engineer Type 10 FSI with an alternative "shoe box" version. The model was used to identify surface vortex activity for both types of inlets as well as a comparison of flow straightening and vortex suppression abilities. A side by side comparison of the two different formed suction inlet designs is presented which is useful when evaluating various station and equipment alternatives in flood control applications.