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<br />( <br />~ <br />~ <br />. <br />I <br />. <br /> <br /> <br />/ /~ / / ~..:/ //1 <br />~ ..... 0"'/ <br />::.... ..... ::~ ..~:~; <br />O ....:.-~~~}1.:..: I, <br />/ ) -;~....:::~?/;;c '."'~ <br />/ / / ~ --:"-~:::.~~~" - - ,. <br />I _ - ---;.::;::::;--.- <br />,0" - -;::::-~"", #' <br />---- -..~-~ - - - ~ <br />e:-~" '" ~ ' <br />___ ",I <br /> <br />. <br />~ <br />I <br /> <br />I <br />l <br />t <br />, <br />t <br />~ <br />~ <br />~ <br />~ <br />f <br /> <br />PROJECTING BARREL <br /> <br />CAST-IN- PLACE CCtlCRETE <br />HEADWA WIN <br /> <br /> <br /> <br />PRECAST END SECTION <br /> <br />/ ) ) ) <br /> <br />END MITERED TO THE SLOPE <br /> <br />Figure I-7--Four standard inlet types (schematic). <br /> <br />water surface elevation may also produce <br />full flow. (figure I-II) Regardless of <br />the cause, the capacity of a culvert <br />operating under pressure flow is affected <br />by upstream and downstream conditions <br />and by the hydraulic characteristics of <br />the culvert. <br /> <br />t <br />~ <br />" <br />- <br />~ <br />. <br />~ <br />t <br /> <br />b. Partlv Full (Free Surface) Flow. <br />Free surface flow or open channel flow <br />may be categorized as subcritical, cri- <br />tical, or supercritical. A determina- <br />tion of the appropriate flow regime is <br />accomplished by evaluating the dimen- <br /> <br />sionless number, F r' called the Froude <br />number: <br /> <br />Fr = V!(gYh)O.6 <br /> <br />In this equation, V is the average <br />velocity of flow, g is the gravitational <br />acceleration, and Yh is the hydraulic <br />depth. The hydraulic depth is calculated <br />by dividing the cross-sectional flow <br />area by the width of the free water sur- <br />face. When F r > 1.0, the flow is <br />supercritical and is characterized as <br />swift. When F r < 1.0, the flow is sub- <br />critical and characterized as smooth and <br /> <br />s <br />