Hydraulics of Closed Conduit Spillways Part XI. Test using Air

The use of air instead of water to evaluate the full flow entrance loss coefficients and pressure coefficients for closed conduit spillways is the subject of this paper. The paper explains that air cannot be used as a substitute for water when the spillway is only part full, gives reasons for using air instead of water, presents background information, compares the water and air equations, develops the compressible flow equations required to analyze the data, and describes the test apparatus and procedure. Verification tests show that identical results can be obtained using either air or water.