If someone has sample problems and any tips/procedures on using these tables - Kings Table & Mannings Table, Can you please post them. or email me at [email protected]
Thanks!
Thanks!
Kings Table & Mannings Table
- Thread starter Suns Den
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G
Guest
^^^ Could you be a little more specifc (e.g. which table you are referring to, reference of the table) - there are actually a lot of tables your description could apply to. Most likely we can create synthetic problems that would allow you to manipulate the table/chart of interest so that you understand the use and nuances.
Regards,
JR
Regards,
JR
JR, The Mannings tables are the ones from Field Engineer Manual - Hydraulics section Pg.428 to 439 taken/refers to Mannings chart - Water & Sewage works, sep 1977 wabash Chicago. The Kings table I am refering to are from the Handbook of Hydraulics - King & Brater pg.7-30 to 7-74 and 8-49 to 8-66
The King's Table was probably invented a few decades ago when engineers still used slide rules. I remember I had one which was not as good as the ones engineering students used (I was in high school). Now I use the HP-33s for the PE exam, it can deal with trapezoidal channel problems.
G
Guest
You are correct that the King and Brater book is old school - first edition was published in 1912. I happened to get a hold of the seventh edition (1996) that was updated for metric units. I ended up with metric units by accident.
The book provides a fair number of quick-n-easy tables that were made for a time when computers weren't available. Certainly, one could program calculators or computers to provide the same analytical results; however, I found that familiarity with the use of those tables and cranking results out made me feel better.
I didn't program any equations into my calculator going into the exam - I am a WEO (Write 'Em Out) kinda guy. It helps me to see the solution layed out to be able to error-check more efficiently. That is me - other folks work better with formulae in a calculator. Each method has it's pros and cons - you just have to find what is comfortable for you.
Suns Den --
I have the tables you are referring to - albeit my tables are in metric. I will work on putting together some problems that would utilize the tables you described.
JR
G
Guest
Yikes !! I haven't done a very good job
hmy:Problem - Trapezoidal Channel (taken from Fundamentals of Fluid Mechanics, page 657)
Water flows in the canal of a trapezoidal cross section that consists of:
Depth of water in channel = 5.0 ft
Bottom of channel = 12.0 ft
Side slope = 40 degrees relative to the x-axis (e.g. bottom of canal)
Bottom Slope = 1.4 ft drop per every 1000 ft of length
Determine the flowrate in the canal if the canal is ( a ) lined with new smooth concrete, and ( b ) if weeds cover the wetted perimeter.
Extra credit: Determine Froude # for each case and classify whether flow as critical or sub-critical.
Answers to be posted upon request.
JR
Sol'n:
Z=1/tan 40 = 1.19
a/ Q=844 cfs
b/ Q=439 cfs
A= B*Y+Z*Y^2=89.75 ft2
T=B+2*Z*Y=23.9 ft
Vsmooth=844/89.75=9.4fps
Vrough=439/89.75=4.89 fps
Hyd depth = A/T=89.75/23.9=3.76 ft
sqrt(g*hyd depth)=11
Fr smooth=9.4/11=0.85
Fr rough=4.89/11=0.44
Flows are subcrit.
Z=1/tan 40 = 1.19
a/ Q=844 cfs
b/ Q=439 cfs
A= B*Y+Z*Y^2=89.75 ft2
T=B+2*Z*Y=23.9 ft
Vsmooth=844/89.75=9.4fps
Vrough=439/89.75=4.89 fps
Hyd depth = A/T=89.75/23.9=3.76 ft
sqrt(g*hyd depth)=11
Fr smooth=9.4/11=0.85
Fr rough=4.89/11=0.44
Flows are subcrit.
Guys: Yesterday I review the open channel flow and tried to understand the King’s chart and used it to solve a problem of finding normal depth of an open channel or pipe (my method is to use the HP calculator but it’s nice to know a back up way to solve this thing). I found out that the King’s chart missed an expression on the horizontal scale needed to solve the normal depth of open channel (or pipe) for steady uniformed flow. Please see the revised King’s chart. The expression is:
Q*n/(1.49*S^(1/2)*b^(8/3)) or Q*n/(1.49*S^(1/2)*do^(8/3))
Q*n/(1.49*S^(1/2)*b^(8/3)) or Q*n/(1.49*S^(1/2)*do^(8/3))
D/b = 5/12 = 0.42Yikes !! I haven't done a very good job
Problem - Trapezoidal Channel (taken from Fundamentals of Fluid Mechanics, page 657)
Water flows in the canal of a trapezoidal cross section that consists of:
Depth of water in channel = 5.0 ft
Bottom of channel = 12.0 ft
Side slope = 40 degrees relative to the x-axis (e.g. bottom of canal)
Bottom Slope = 1.4 ft drop per every 1000 ft of length
Determine the flowrate in the canal if the canal is ( a ) lined with new smooth concrete, and ( b ) if weeds cover the wetted perimeter.
Extra credit: Determine Froude # for each case and classify whether flow as critical or sub-critical.
Answers to be posted upon request.
JR
H/V = 1.2
S = 0.0014
K ~ 4 (kings table)
using Q = K/n*D^8/3*S^1/2
Q1 = 841 cfs
Q2 = 312 cfs (assuming n = 0.035)
Fr1 = 0.315 <1 Subcritical flow
Fr2 = 0.85 <1 Subcritical flow
G
Guest
Sure ... btw V/H = 1.2 and D/b = 0.42 is correct.
a)
n = 0.012 (assumed)
Q = 915 cfs (for K = 4.0, Q = 910 cfs)
v = 10.2 fps
Fr = 0.804 <1 ; therefore subcritical
B)
n = 0.030 (assumed)
Q = 366 cfs (for K = 4.0, Q = 365 cfs)
v = 4.08 fps
Fr = 0.322 < 1; therefore subcritical
JR
a)
n = 0.012 (assumed)
Q = 915 cfs (for K = 4.0, Q = 910 cfs)
v = 10.2 fps
Fr = 0.804 <1 ; therefore subcritical
B)
n = 0.030 (assumed)
Q = 366 cfs (for K = 4.0, Q = 365 cfs)
v = 4.08 fps
Fr = 0.322 < 1; therefore subcritical
JR
Last edited:
good old n value assumptions
my assumption for - lined with new smooth concrete was 0.013
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