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Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

Q2 Z2,(Q2) Z2(Q2) - Institute for Water Resources - U.S. Army

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ilotilla. These assumptions will not always.:be realized in ptactice,<br />

anj one would like to know whether the <strong>for</strong>mula can be applied without .<br />

resulting in large errors.<br />

Howe's. •speed function has been applied ta two sets of data. The<br />

first is composed of tests per<strong>for</strong>med by the <strong>Army</strong> Corps of Engineers<br />

with a 1500-horsepower towboat pushing tows of 4 and 8 fully integrated<br />

and semi-integrated barges 'These tests were per<strong>for</strong>med in 1947 on<br />

reaches of the lower Illinois and Upper Mississippi. All variables<br />

necessary to the application of Howe's <strong>for</strong>mula were carefully recorded<br />

by Corps personnel, except <strong>for</strong> stream velocity. Stream velocity was<br />

assumed to be 2 feet per second or 1.36 miles per hour. This assump-<br />

tion was based on discussions with two Corps hydrology experts who in-<br />

dependently advanced this figure as a good "approximate average." A<br />

better estimate of stream velocity would require obtaining the dis-<br />

charge of the waterway (in cubic feet per second), obtaining an approxi-<br />

mation of the cross section of the waterway (in square feet), and di-<br />

viding the latter into the <strong>for</strong>mer. The resulting velocity in feet per<br />

second could then be trans<strong>for</strong>med into a mile-per-hour equivalent.<br />

While such a calculation is possible, it would add little, <strong>for</strong> the<br />

tests all occurred within a few days of one another over the same<br />

stretches of the two waterways involved. These data contained 24 ob-<br />

servations, half upstream and half downstream. The ranges of the vari-<br />

ables are shown below:<br />

(1) i<strong>for</strong>-sepOWCI-1- 1500— " "1 •<br />

, (21-1.epgth of,flotilla: ..390 feet and 780 feet<br />

Zet.a 1.111" a teLL ialyS Or<br />

l 0 eet<br />

one 11<br />

(3) r)readth of tlotfta: . / 'f<br />

one .v:.<br />

•<br />

.RS•_fjoti7.1.4;<br />

(5)'- Depth - of igAer . 91".S.-1 le'ety-'36.15" feet<br />

•<br />

servaT-4ons.<br />

(A) Width<br />

ialz<br />

of channel: • 700 feet-1500 feet<br />

-<br />

(7), Stream velocity: 1.36 miles per hour (assumed).<br />

ar , •<br />

74

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