The Six-Inch Water Tunnel at the St. Anthony Falls Hydraulic Laboratory and Its Experimental Use in Cavitation Design Studies

Abstract

A recirculating model water tunnel has been devised at the St. Anthony Hydraulic Laboratory for the purpose of determining prototype design data for use in the planning of various types of cavitation test facilities. The test section of the model is 6 in. in diameter, and various boundary geometries have been studied in their relation to the test stream flow quality. Special emphasis has been given to the cavitation test limits imposed by the test section boundaries and various other tunnel components. This paper describes the basic tunnel, the critical cavitation tests made on the tunnel, and some cavitation studies made in the tunnel. Observations made on closed (cylindrical and diverging), open, and slotted0wall test sections are discussed. A minimum cavitation index of about 0.023 can be achieved in the diverging closed-jet test section at a velocity of 50 fps.

Some cavitation studies indicate how the cavitation susceptibility of the tunnel water varies, and show that the critical cavitation index of a slender body is more constant when based on a measured pressure than when based on vapor pressure.