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Publication Number: FHWA-HRT-07-036
Date: March 2007

Junction Loss Experiments: Laboratory Report

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Publication No. FHWA-HRT-07-036

December 2006

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FOREWORD

The junction loss study described in this report was conducted at the Federal Highway Administration (FHWA) hydraulics laboratory. Between 1986 and 1992, Chang et al. conducted a lab study of energy losses through junction access holes, using relatively large-scale (one-quarter scale) physical models.(1) A preliminary method for determining such losses, based on early results from that study, was published in the Federal Highway Administration's (FHWA) Urban Drainage Design Manual (Hydraulic Engineering Circular No. 22 (HEC 22)).(2)FHWA plans to update HEC 22 and further develop computer software for storm drain design. The need for consistent technology in FHWA publications and software applications on this subject is urgent. To accommodate that need and overcome some of the difficulties in estimating energy loss in access holes, the FHWA's Office of Bridge Technology initiated this study to validate Roger Kilgore's proposed method for computing access hole energy losses. This report will be of interest to hydraulic engineers involved in storm drain design and to researchers involved in developing improved storm drain design guidelines. It is being published as a Web document only.

Gary L. Henderson
Director, Office of Infrastructure
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.

FHWA-HRT-07-036

2. Government Accession No.

3. Recipient's Catalog No.

N/A

4. Title and Subtitle

Junction Loss Experiments: Laboratory Report

5. Report Date

March 2007

6. Performing Organization Code

N/A

7. Author(s)

Kornel Kerenyi, J. Sterling Jones, and Stuart Stein

8. Performing Organization Report No.

N/A

9. Performing Organization Name and Address

GKY and Associates, Inc.
5411-E Backlick Road
Springfield, VA 22151

10. Work Unit No. (TRAIS)

N/A

11. Contract or Grant No.

DTFH-04-C-00037

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Laboratory Report
March 2004–May 2006

14. Sponsoring Agency Code

FHWA Task Order 10

15. Supplementary Notes

Contracting Officer's Technical Representative (COTR): Sheila Duwadi, HRDI-07
Karsten Sedmera summarized the results and described the procedures used in this study. Holger Dauster, Matthias Poehler, and Amon Tarakemeh provided invaluable assistance with instrumentation, data collection, and analysis.

16. Abstract

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 three-dimensional (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 more organized 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.

17. Key Words

Energy loss, junction loss, storm drain, access hole, manhole, hydraulics, physical model.

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service (NTIS), Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

63

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

SI (Modern Metric) Conversion Factors

TABLE OF CONTENTS

1. INTRODUCTION

2. THEORY

3. EXPERIMENTAL SETUP

4. RESULTS

5. CONCLUSIONS

APPENDIX A. VELOCITY PROFILES AT 5 MM INCREMENTS

APPENDIX B. VELOCITY PROFILES USED IN THE MINICULVERT RUNS

APPENDIX C. VELOCITY PROFILES USED IN THE ACCESS HOLE RUNS

REFERENCES

LIST OF FIGURES

Figure 1. Photo. Typical access hole
Figure 2. Diagram. Cross-section definition sketch of an access hole
Figure 3. Diagram. Flow chart for the proposed junction loss method
Figure 4. Photo. Access hole prototype in the 1986–1992 study with the lab technician to show relative size
Figure 5. Photo. The scaled model of an access hole equipped with standpipe instruments
Figure 6. Photo. CIS sensors attached to standpipes
Figure 7. Diagram. Stereoscopic PIV arrangement and the access hole setup
Figure 8. Diagram. Eleven stereoscopic PIV measurements along the miniculvert outflow pipe
Figure 9. Photo. Access hole setup with PIV light sheet in outflow pipe
Figure 10. Photo. Closeup of the tracer particles in the outflow pipe from the access hole
Figure 11. Graph. Effects of scaling
Figure 12. Image. Selected contours of velocity magnitude in the outflow pipe
Figure 13. Graph. Correlation of ∆Eoc and A86.6
Figure 14. Graph. Correlation of ∆Eoc and A90
Figure 15. Graph. Correlation of ∆Eoc and A92.5
Figure 16. Graph. Outflow (entrance) loss versus velocity head
Figure 17. Graph. Inflow (exit) loss versus velocity head
Figure 18. Graph. Validation of total energy loss calculations
Figure 19. Graph. Validation of EGL with a 180° inflow pipe and supercritical outflow
Figure 20. Graph. Validation of EGL with a 90° inflow pipe and supercritical outflow
Figure 21. Graph. Validation of EGL with two inflow pipes and supercritical outflow
Figure 22. Graph. Validation of the total energy loss with plunging inflow
Figure 23. Graph. EGL in the inflow pipe versus plunging inflow rate for Ea = 1.5Do
Figure 24. Graph. EGL in the inflow pipe versus plunging inflow rate for Ea = 3.0Do
Figure 25. Image. Example velocity profile at the outlet
Figure 26. Image. Example velocity profile 5 mm (0.19 inch) from the outlet
Figure 27. Image. Example velocity profile 10 mm (0.39 inch) from the outlet
Figure 28. Image. Example velocity profile 15 mm (0.59 inch) from the outlet
Figure 29. Image. Example velocity profile 20 mm (0.79 inch) from the outlet
Figure 30. Image. Example velocity profile 25 mm (0.98 inch) from the outlet
Figure 31. Image. Example velocity profile 30 mm (1.18 inches) from the outlet
Figure 32. Image. Example velocity profile 35 mm (1.38 inches) from the outlet
Figure 33. Image. Example velocity profile 40 mm (1.57 inches) from the outlet
Figure 34. Image. Example velocity profile 45 mm (1.77 inches) from the outlet
Figure 35. Image. Example velocity profile 50 mm (1.97 inches) from the outlet
Figure 36. Image. Velocity profile at the outlet for Q/Ao = 42 cm/s (16 inches/s)
Figure 37. Image. Area where V is greater than 0.867Vmax at the outlet for Q/Ao = 42 cm/s (16 inches/s)
Figure 38. Image. Area where V is greater than 0.90Vmax at the outlet for Q/Ao = 42 cm/s (16 inches/s)
Figure 39. Image. Area where V is greater than 0.925Vmax at the outlet for (16 inches/s) Q/Ao = 42 cm/s (16 inches/s)
Figure 40. Image. Velocity profile 5mm (0.19 inch)from the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 41. Image. Area where V is greater than 0.867Vmax 5mm (0.19 inch) from the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 42. Image. Area where V is greater than 0.90Vmax 5mm (0.19 inch) from the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 43. Image. Area where V is greater than 0.925Vmax 5mm (0.19 inch) from the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 44. Image. Velocity profile at the outlet for Q/Ao = 69 cm/s (27 inches/s)
Figure 45. Image. Area where V is greater than 0.867Vmax at the outlet for Q/Ao = 69 cm/s (27 inches/s)
Figure 46. Image. Area where V is greater than 0.90Vmax at the outlet for Q/Ao = 69 cm/s (27 inches/s)
Figure 47. Image. Area where V is greater than 0.925Vmax at the outlet for Q/Ao = 69 cm/s (27 inches/s)
Figure 48. Image. Velocity profile 5 mm (0.19 inch) from the outlet for Q/Ao = 43 cm/s (17 inches/s)
Figure 49. Image. Area where V is greater than 0.867Vmax 5 mm (0.19 inch) from the outlet for Q/Ao = 43 cm/s (17 inches/s)
Figure 50. Image. Area where V is greater than 0.90Vmax 5 mm (0.19 inch) from the outlet for Q/Ao = 43 cm/s (17 inches/s)
Figure 51. Image. Area where V is greater than 0.925Vmax 5 mm (0.19 inch) from the outlet for Q/Ao = 43 cm/s (17 inches/s)
Figure 52. Image. Velocity profile at the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 53. Image. Area where V is greater than 0.867Vmax at the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 54. Image. Area where V is greater than 0.90Vmax at the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 55. Image. Area where V is greater than 0.925Vmax at the outlet for Q/Ao = 57 cm/s (22 inches/s)
Figure 56. Image. Velocity profile at the outlet for Q/Ao = 64 cm/s (25 inches/s)
Figure 57. Image. Area where V is greater than 0.867Vmax at the outlet for Q/Ao = 64 cm/s (25 inches/s)
Figure 58. Image. Area where V is greater than 0.90Vmax at the outlet for Q/Ao = 64 cm/s (25 inches/s)
Figure 59. Image. Area where V is greater than 0.925Vmax at the outlet for Q/Ao = 64 cm/s (25 inches/s)
Figure 60. Image. Velocity profile at the outlet for Q/Ao = 75 cm/s (30 inches/s)
Figure 61. Image. Area where V is greater than 0.867Vmax at the outlet for Q/Ao = 75 cm/s (30 inches/s)
Figure 62. Image. Area where V is greater than 0.90Vmax at the outlet for Q/Ao = 75 cm/s (30 inches/s)
Figure 63. Image. Area where V is greater than 0.925Vmax at the outlet for Q/Ao = 75 cm/s (30 inches/s)

LIST OF TABLES

Table 1. Values for the Coefficient CB
Table 2. Distance along the culvert outflow pipe where Ak was measured
Table 3. Total energy loss across the access hole
Table 4. Distance along the access hole outflow pipe where Ak was measured
Table 5. Parameters for the 15 base runs

LIST OF SYMBOLS

A area (m2 (ft2)).

Ac contracted area (m2 (ft2)).

Ao cross-sectional area of the outlet pipe (m2 (ft2)).

Ak cross-sectional area associated with a contour of velocity (m2 (ft2)).

b access hole or junction chamber diameter (m (ft)).

C energy loss coefficient (dimensionless).

CB energy loss coefficient for benching (dimensionless).

Cθ energy loss coefficient for angled inflow (dimensionless).

CH energy loss coefficient for plunging inflow (dimensionless).

DI discharge intensity (dimensionless).

Do outlet pipe diameter (m (ft)).

Ea final calculated energy level (m (ft)).

Ea1 initial energy level in the access hole (m (ft)).

Ea,ff estimated access hole energy level for full flow (m (ft)).

Ea,ics estimated access hole energy level for submerged inlet control (m (ft)).

Ea,icu estimated access hole energy level for unsubmerged inlet control (m (ft)).

Ei energy at the inlet (m (ft)).

Eo total energy calculated for the upstream end of the outlet pipe (m (ft)).

ΔE additional energy loss for ΔEB, ΔEθ, and ΔEH (m (ft)).

ΔEB additional energy loss for benching (floor configuration) (m (ft)).

ΔEθ additional energy loss for angled inflows other than 180 degrees (m (ft)).

ΔEH additional energy loss for plunging flows (m (ft)).

ΔEi exit energy loss (m (ft)).

ΔEoc energy loss in the outflow pipe (m (ft)).

HL,i inflow loss (m (ft)).

HL,o outflow loss (m (ft)).

Hk plunge height (m (ft)).

g acceleration due to gravity (m/s2 (ft/s2)).

Ki exit loss coefficient (dimensionless).

Ko entrance loss coefficient (dimensionless).

Po outlet pressure head (m (ft)).

Qflow (m3/s (ft3/s)).

Qi inlet flow (m3/s (ft3/s)).

Qj nonplunging inflow (m3/s (ft3/s)).

Qk plunging inflow (m3/s (ft3/s)).

Qo Outlet flow (m3/s (ft3/s)).

Vi inflow velocity (m/s (ft/s)).

Vo outflow velocity (m/s (ft/s)).

Vo 2/2g outlet velocity head (m).

ya water depth (m (ft)).

ya1 estimated structure water depth (m (ft)).

yo outlet flow depth (m (ft)).

zk plunging inlet elevation (m (ft)).

zo outlet pipe invert elevation (m (ft)).

γ specific weight of water (N/m3 (lb/ft3)).

θj inflow angle (degrees).

θw flow-weighted angle (degrees).

ABBREVIATED GLOSSARY

CCD charge coupled device.

CIS contact image sensors.

EGL energy grade line.

HEC Hydraulic Engineering Circular.

HGL hydraulic grade line.

PIV particle image velocimetry.

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). The hydraulics and hydrology research program at the TFHRC Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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