EXPERIMENTS ON FLOW THROUGH INLET GRATINGS FOR STREET GUTTERS, WITH DISCUSSION

IN ORDER TO STUDY FLOW TO THROUGH INLETS, A TEST GUTTER WITH A CROSS-SLOPE OF 20.6 TO 1 AND WITH A NEARLY VERTICAL CURB WAS CONSTRUCTED IN THE 36-IN. TILTING CHANNEL OF THE LABORATORY. NEAR THE END OF THE GUTTER, A TEST SECTION WAS PROVIDED, IN WHICH FULL-SCALE INLETS AND CURB OPENINGS OF ANY SHAPE COULD BE INSTALLED. TESTS OF VARIOUS GRATE INLETS WERE CONDUCTED AT SEVERAL SLOPES, USING A WIDE RANGE OF DISCHARGES AT EACH SLOPE. IN ALL TESTS THE ENTIRE FLOW WAS INTRODUCED AT THE UPPER END OF THE GUTTER. MEASUREMENTS WERE TAKEN OF THE DEPTH AND DISCHARGE IN THE GUTTER, AND OF THE QUANTITY OF WATER PASSING OVER AND AROUND THE INLET, WHICH WAS TERMED "CARRYOVER". THE PORTION OF THE FLOW INTERCEPTED BY THE INLET, REFERRED TO AS "INLET CAPACITY", WAS THE DIFFERENCE BETWEEN THE GUTTER FLOW AND THE CARRYOVER. TESTS WERE ALSO MADE WITH SIMULATED DEBRIS ADDED TO THE FLOW. IN AN ATTEMPT TO IMPROVE THE SELF-CLEANING ABILITY OF GRATE INLETS, AN EXPERIMENTAL INLET WAS CONSTRUCTED WITH ITS BARS AND OPENINGS SET AT A 45 DEGREE ANGLE. TESTS WERE MADE OF THIS INLET BOTH WITH AND WITHOUT A CURB OPENING. THIS EXPERIMENTAL INLET WAS THEN IMPROVED BY ROUNDING THE SURFACE OF EACH OF ITS BARS. STANDARD INLETS TESTED INCLUDED A MINNESOTA HIGHWAY DEPARTMENT INLET, WHICH HAS OPENINGS PARALLEL TO THE FLOW, AND A CITY STREET DEPARTMENT INLET, WHICH HAS OPENINGS NORMAL TO THE DIRECTION OF FLOW. FROM THESE TESTS THE FOLLOWING OBSERVATIONS WERE MADE: (1) THE CAPACITY OF A GRATE INLET CAN BE GREATLY INCREASED BY ALLOWING A SMALL AMOUNT OF CARRYOVER. (2) THE CAPACITY OF A GRATE INLET IS DETERMINED MAINLY BY ITS WIDTH NORMAL TO THE FLOW AND BY THE EFFICIENCY OF ITS OPENINGS. (3) THE EFFICIENCY OF GRATE INLET OPENINGS DEPENDS LARGELY ON THE EFFECTIVE LENGTH OF THE OPENINGS IN THE DIRECTION OF FLOW. (4) THE CAPACITY OF INLETS WITH TRANSVERSE BARS AND OPENINGS CAN BE INCREASED SUBSTANTIALLY BY ROUNDING THE TOP SURFACE OF EACH BAR. (5) IN THE NORMAL RANGE OF APPLICATION, INLETS WITH EFFICIENT OPENINGS OPERATE WITH INCREASING CAPACITY AS THE SLOPE OF THE GUTTER IS INCREASED. (6) EXCEPT WHERE CAPACITY IS PROVIDED BY PONDING, CURB OPENINGS ARE OF LITTLE OR NO VALUE IN INCREASING THE CAPACITY OF A GRATE INLET. /AUTHOR/

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/hrbresearchrpts/1948/6B-004.pdf
• Supplemental Notes:
  • Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved.
• Authors:
  • Larson, Curtis L
• Discussers:
  • Izzard, Carl F
• Publication Date: 1948-12

Media Info

• Media Type: Digital/other
• Features: Figures;
• Pagination: 13p
• Monograph Title: Surface drainage of highways
• Serial:
  • Highway Research Board Research Reports
  • Issue Number: 6B
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Culvert inlets; Debris removal; Drains; Flow; Grates; Laboratory tests
• Uncontrolled Terms: Debris; Inlets
• Subject Areas: Highways; Hydraulics and Hydrology;

Filing Info

• Accession Number: 00204414
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: May 29 1972 12:00AM