Junction Loss Experiments: Laboratory Report

The current study has two objectives. The first is to evaluate Roger Kilgore’s proposed procedure, which requires conducting some of the same types of tests that were run in the previous study. The new tests conducted include a wider range of parameters, such as greater plunge-height ratios and steeper pipe slopes. Previous research was limited in that it was applicable to storm drain systems located only in relatively flat areas; the research would not hold up for systems in hilly and mountainous regions of the country where steep pipe slopes are the norm.The second and more challenging objective is to characterize the energy level in an access hole. If that can be accomplished, then the familiar culvert hydraulics analyses can be applied to the access hole that serves as the tailbox where inflow pipes enter and to the headbox for outflow pipes where the water exits. Researchers have attempted numerous analyses of particle image velocimetry (PIV) data and threedimensional(3–D) numerical model data, with uneven results. Characterizing energy in the access hole is highly problematic because the flow is so chaotic, and arbitrary assumptions had to be made to obtain results that fall between intuitive limits. Researchers at the FHWA lab now have investigated the moreorganized flow in the contracted area of the outflow pipe, using the contraction ratio as an indirect measure of the contraction loss in the flow from the access hole to the outflow pipe to backcalculate the energy loss in the access hole.