SEVENTH PROGRESS REPORT ON HYDRAULICS OF CULVERTS. TAPERED BOX CULVERT INLETS WITH FALL CONCENTRATION IN THE INLET STRUCTURE

THE PERFORMANCE OF TAPERED BOX CULVERT INLETS IN WHICH A PART OF THE BARREL FALL IS CONCENTRATED IN THE INLET STRUCTURE BETWEEN THE FACE AND THROAT SECTIONS WAS ANALYZED. EXPERIMENTAL DATA ARE PRESENTED ONLY FOR ENTRANCE CONTROL OPERATION. IN THIS CONNECTION, A CULVERT BARREL AND INLET STRUCTURE IS CONSIDERED TO BE OPERATING IN ENTRANCE CONTROL IN A GIVEN POOL LEVEL RANGE WHEN THE FLOW CONTROL SECTION, OR THE GEOMETRY ELEMENTS WHICH DEFINE OR CONTROL THE HEAD- DISCHARGE RELATIONSHIP, LIE WITHIN OR FORM A PART OF THE ENTRANCE OR INLET STRUCTURE. EXPERIMENTAL RESULTS SHOW THAT TAPERED INLETS WITH FALL CONCENTRATIONS IN THE INLET STRUCTURE ARE SIGNIFICANTLY LESS EFFICIENT IF THE BEND SECTION IS INSTALLED COINCIDENT WITH THE THROAT SECTION RATHER THAN UPSTREAM OF THAT SECTION. MATHEMATICAL ANALYSIS IS PRESENTED INDICATING THE CONTROL INFLUENCE OF THE DIMENSIONS OF THE BEND SECTION ON THE PERFORMANCE OF INLETS. THE EXPERIMENTAL DATA PRESENTED FOR FREE SURFACE FLOW IN TAPERED INLETS PROVIDING THE CONCENTRATION OF FALL IN THE INLET STRUCTURE YIELD DIRECTLY APPLICABLE DATA FOR A VARIETY OF INLET GEOMETRIES AND PERMIT ESTIMATES OF PERFORMANCE OVER A RANGE OF SIMILAR INLET GEOMETRY VARIATIONS. EXPERIMENTAL DATA ALSO SHOW THAT A PART OF THE AVAILABLE BARREL FALL MAY BE CONCENTRATED IN INLET STRUCTURES OF SPECIFIC TYPES WITH CONSEQUENT SUBSTANTIAL INCREASE IN PERFORMANCE OF THE INLET STRUCTURE, PROVIDED THE INLET STRUCTURE IS DIMENSIONED IN SUCH FASHION AS TO PRODUCE THROAT CONTROL OPERATION.