TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME

The distance required for flow entering a laboratory channel to become fully-developed and uniform can be substantial. Given the need to establish fully-developed uniform flow, if the length of a laboratory channel is not substantial then it likely that the flume cannot be used to conduct open-chann...

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Main Author: Sapkota, Deependra
Format: Others
Published: OpenSIUC 2015
Subjects:
Online Access:https://opensiuc.lib.siu.edu/theses/1801
https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=2815&context=theses
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spelling ndltd-siu.edu-oai-opensiuc.lib.siu.edu-theses-28152018-12-20T04:39:24Z TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME Sapkota, Deependra The distance required for flow entering a laboratory channel to become fully-developed and uniform can be substantial. Given the need to establish fully-developed uniform flow, if the length of a laboratory channel is not substantial then it likely that the flume cannot be used to conduct open-channel flow research. In laboratory studies where the channel bed is hydraulically rough, the noted problem can be lessened by minimizing the length over which the flow becomes fully-developed and uniform (Lunif). For this study it is hypothesized that if bed material with a roughness height (ks, ∆) is placed at the channel entrance and ks, ∆ is greater has the roughness height of bed material placed throughout the channel (ks, bed) then Lunif can be reduced. The length over which the larger bed material is referred to as the tripping zone length (∆). A second hypothesis for this study is that if ∆ is longer, then Lunif will be shorter. The primary objective of this study is to test the above mentioned hypothesis and to develop a relationship for predicting Lunif as a function of Δ. For this study, physical tests were performed in a rectangular Plexiglas flume with a variable slope. The flume was 6.1 m long, 45.7 cm wide, and 45.7 cm deep. The channel has smooth walls and the bed was lined with gravel (median particle size, d50 = 8.5 mm or 22 mm). Similarly tripping zone was lined with gravel of larger size (median particle size, d50 = 13 mm or 58 mm).Twelve tests were conducted for the study. For each test, longitudinal point velocity measurements (u) were made along the channel center, at five elevations (z), and at twelve longitudinal stations (x). An Acoustic Doppler Velocimeter was used to measure u. Lunif was determined by considering four indications of flow uniformity. Results indicate that having a tripping zone decreases Lunif and the magnitude of the decrease in Lunif was dependent on ∆. A function is presented for predicting Lunif /H = f (Rep, Fr, and Δ/H) where Rep is the Reynold's particle number, Fr is the Froude number and H is the flow depth. 2015-12-01T08:00:00Z text application/pdf https://opensiuc.lib.siu.edu/theses/1801 https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=2815&context=theses Theses OpenSIUC Rough Turbulent Flow Tripping of Boundary Layer Development Length Uniform Flow
collection NDLTD
format Others
sources NDLTD
topic Rough Turbulent Flow
Tripping of Boundary Layer Development Length
Uniform Flow
spellingShingle Rough Turbulent Flow
Tripping of Boundary Layer Development Length
Uniform Flow
Sapkota, Deependra
TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
description The distance required for flow entering a laboratory channel to become fully-developed and uniform can be substantial. Given the need to establish fully-developed uniform flow, if the length of a laboratory channel is not substantial then it likely that the flume cannot be used to conduct open-channel flow research. In laboratory studies where the channel bed is hydraulically rough, the noted problem can be lessened by minimizing the length over which the flow becomes fully-developed and uniform (Lunif). For this study it is hypothesized that if bed material with a roughness height (ks, ∆) is placed at the channel entrance and ks, ∆ is greater has the roughness height of bed material placed throughout the channel (ks, bed) then Lunif can be reduced. The length over which the larger bed material is referred to as the tripping zone length (∆). A second hypothesis for this study is that if ∆ is longer, then Lunif will be shorter. The primary objective of this study is to test the above mentioned hypothesis and to develop a relationship for predicting Lunif as a function of Δ. For this study, physical tests were performed in a rectangular Plexiglas flume with a variable slope. The flume was 6.1 m long, 45.7 cm wide, and 45.7 cm deep. The channel has smooth walls and the bed was lined with gravel (median particle size, d50 = 8.5 mm or 22 mm). Similarly tripping zone was lined with gravel of larger size (median particle size, d50 = 13 mm or 58 mm).Twelve tests were conducted for the study. For each test, longitudinal point velocity measurements (u) were made along the channel center, at five elevations (z), and at twelve longitudinal stations (x). An Acoustic Doppler Velocimeter was used to measure u. Lunif was determined by considering four indications of flow uniformity. Results indicate that having a tripping zone decreases Lunif and the magnitude of the decrease in Lunif was dependent on ∆. A function is presented for predicting Lunif /H = f (Rep, Fr, and Δ/H) where Rep is the Reynold's particle number, Fr is the Froude number and H is the flow depth.
author Sapkota, Deependra
author_facet Sapkota, Deependra
author_sort Sapkota, Deependra
title TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
title_short TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
title_full TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
title_fullStr TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
title_full_unstemmed TRIPPING OF THE BOUNDARY LAYER DEVELOPMENT LENGTH OVER ROUGH AND FULLY TURBULENT SUBCRITICAL FLUME
title_sort tripping of the boundary layer development length over rough and fully turbulent subcritical flume
publisher OpenSIUC
publishDate 2015
url https://opensiuc.lib.siu.edu/theses/1801
https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=2815&context=theses
work_keys_str_mv AT sapkotadeependra trippingoftheboundarylayerdevelopmentlengthoverroughandfullyturbulentsubcriticalflume
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