Download Manning’s Roughness Coefficient(n) PDF

TitleManning’s Roughness Coefficient(n)
TagsCivil Engineering Hydraulic Engineering Materials Science Gases Hydrology
File Size1.2 MB
Total Pages11
Document Text Contents
Page 1

Experiment # 1

To determine the Manning’s Roughness Coefficient(n)
& Chézy Coefficient(c) in laboratory flume

 Purpose:

 To study changes in Manning’s Roughness coefficient (n) by varying discharge (Q) in

flume.

 To study changes in Chezy Coefficient(c) by varying discharge (Q) in flume.

 To investigate relation between Manning Roughness Coefficient(n) & Chezy Coefficient

(c)

 To determine Manning Roughness Coefficient(n) and Chezy Coefficient (c)



 Apparatus :

i. S6 glass sided tilting flume

Note: In this type of flume we can adjust

positive as well as negative slope. Positive

slope ranges between 0 to 1:40 and negative

upto 1:200.The bad of the flume is made up of

cold formed steel. Length of the channel is 7.5

m.

ii. Point Gauge

iii. Differential Manometer



 Related Theory:

1) Uniform Flow:

That type of flow in which flow perimeters and channel perimeters remain constant as

a function of distance between two cross sections. In uniform flow, depth and velocity

remain constant along the flow direction for the given discharge in the given channel. We

can say that it is only possible in prismatic channels.



2) Non-Uniform Flow:

That type of flow in which flow perimeters and channel perimeters do not remain

constant as a function of distance between two cross sections.

Page 2

http://en.wikipedia.org/wiki/Gravity
http://en.wikipedia.org/wiki/Irish_people
http://en.wikipedia.org/wiki/Engineer
http://en.wikipedia.org/wiki/Robert_Manning_(engineer)
http://en.wikipedia.org/wiki/U.S._customary_units
http://en.wikipedia.org/wiki/SI_units

Page 5

Observations and Calculations

Formulas

Manning’s formula

vavg=
𝛼

𝑛1
× Rh

2/3
× S0

1/2


vavg=
𝛼

𝑛2
× Rh

2/3
× S1/2



Chaezy’s formula

vavg =𝑐1√𝑅𝑆0

vavg =𝑐2√𝑅𝑆



Hydraulic radius =Rh = A/P ; Area of flow of water= A=b x yavg

Depth = yavg = (y1+y2+y3)/3 ; Wetted perimeter = P = b + 2yavg

S = Slope of Energy line ; Sw= Slope of Hydraulic Grade Line

S0=Slope of Channal Bed ; vavg= Average Velocity

For uniform flow conditions S = S0 = Sw

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