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i~ • I f } • ~I 1 TRAPEZOIDAL AND CIRCULAR CHANNEL ANALYSIS HYDROCALC HVDRAUUCS MANUAL, PAGE 17 :. .. ... ... ... .. ~ .- ~~..~~~::is~~:.:.:.::~CIRCUI.AR~~CAANNEL~: ANALYSIS~~..;..~:.;:':;~:~.:~:~..:~:~..:' . .. '.::::~:.::..':.~, :...~~.: ~:::.:::! :... .. , .. :. ..: ~..: .: ~..: ~~~~~... ... .: ~:.~.NORMAL~~'DEPTH.CO[~UTATIOti':~:~~~.:::~::.~::.~.:.~:: ~. : ::::.~;.: ~.i:"~.~. :~~ ~ ~~ :..:.:• ~.:`.'~.Flow Rate~~:(cubic: feet:::per.:aecondl~:;`:~::.:..~.::..~'~~~:~:::~~~:.;.:~~ .:.:.:.:.::.:::::: . ~ ~ ~ ~ ~ ;.::::::~ ::.:.:; ~:.`::::. :~.:~~G00~~'~ ... .... ..... .~.~ ~~.~ : ~':.~:~:.: ~.. ~: ~ - ~~~~. ':.~~.::Channel ~BOttom~S'16pe:::f:feet:~~ er;~~footl~~'..~:..::":.~:::.:'~~~: p .;.;~ . 0.01 Planning `s .Roughness:: Coefficient ::.(n-value l..' . ::.:..:::: ..'.';::: ~ :: 0.:15:'::'':;::: :":'..:.'..::.:: ~~~ ~~~ ~~'~:'Channel_'Diameter'~.(feet ~:~~~~~~:::;.:' ~~ ~~ ~ ~ : ; ~~ ~ ~ ~ ~.::..~~.:.:::';':::'':... :.:: ~:..:'.::;'t,r3:~::::AESULT ~.~~:le::i;';~'::..:~-; ~ ~ .;. . . .: , :- ::-: ::::;:.i:.::~~..::,~~`: ~.; ?:: ::~: .:..:..: :: ~. ~:~ :: ~ ~ ~ ~ ~ ~ . . ..:... .: ~ ......:..: ~ ~:~: ~:::NORPSAL ~~ SS7'sPTR:~ ~ (FEET 7 ~:. ~ ~ ". ~.::.:~::. ':: ;:::..::~~ ~ ~~.:;~.:.~ ~.:~:.:: ~."::...:::'`:~ ~ : ~.:~ ~~ ~~:::: ~ ~.:~ ~:'~~~~ ~:::::~-.:~~: ~ ....... . .. :... ..: : : ; . 'r, ~.~.:; .......4:03 ;.::::~::~,~,::... ..... ow~~.Veloc 't :: feet'. a .:'second :; Fl...:.... .. ~. Y...( .. ~ ~ ~ :~.'~:15:::77~i:~.:::~~~~"~:~: ~~'~~?~~::`~:~~::::~~ .:... ..... .. . : ~ ~ ~ ~ :::.: .:::: :~::.::::;:~:..;~;::...~'::..:~`:.::~~:.~; ,~. ~. ...~.`~.. ~:Froude Number::.....~::~:~::::-.:~;.:~:.::~:,~:'~::'.:~:;::~::~:. :;, .; ~ :::: ::~:: :.: ~.:::.':~~ : ~::.~ :Velocity : Head ~.: l feet 1~ ~.:~'':::~,_.~.~~:`~:'.:::~: ~~. ~.:~: ~ :::.::,:.:. ~.~:.: ~. ~.'':~ ;;.` ~...:.::: ~..`:::.:::.:::'::.:.:.':.:::: ..:~'~: ~.~~~:~~ 3:: S 6 ~::"..<::~~:~~ ~:..?: ' `~::~::; Enei .Head.:: feet :: ( ).:. 9Y . 7:: Et4 :::::: :. :.::::... r .::.;CZOSS=Sectional':Area.of`.::F2ow.:.tsquare.: feet):::.':: '?+.';.:::',::, :'.:: ;.25::,3:7::::;:`:r::::.;;": ;:::: ;..:To .Width: of Flow: .feet ::::;::::>:>; ? .:::::::.::::::':.;::::.:::::;:.::`:::::::'::::`::; P.... {. ....:~ .:: .::: ,.... '::`::;:::,.:8::00 __:;'..'.::::i:`::..::;:;;;.;. .;:::.::.::'::<::<Enter>::::Repeat,:<R>epa~t~:or.':<Esc>-::$d.'::;: ;`;r:;.:'::::':::•.-z .:::.::::::::.:.>:. Flgure 2-4 Example of Normal Depth fn Circular Channel Using Chart 51 of the FHWA's "Design Charts for Open-Channel Flow" (FHWA 1961), the Normal Depth of flow in the clrculaz channel under the stated conditions 1s approadmately 4 feet The flow velocity is approximately 16 feet per second. As indicated !n Figure 2-4, the Circular Channel Analysts program provides the same results. 2.2 CRITICAL DEPTH FOR TRAPEZOIDAL OR CIRCULAR CHANNELS Critical Depth occurs when the flow Sn a channel has minimum specific energy. Specific Energy refers to the sum of the depth of flow and the velocity head. At Critical Depth. the velocity head 1s equal to one-half the average depth of flow. Critical Depth depends only on the channel shape and flow rate. It is sometimes useful to compute Critical Depth in order to analyre the type of flow proflle which will occur >n a particular channel. 2.2.1 RE6lUIRED INPUT DATA FOR CRITICAL DEPTH PROCEDURE in order to compute the Critical Depth of flow in a channel, the program requires that you supply the following items of input data: 1) The Flow Rate >n the channel. 2) The Manning's Roughness Coefficient for the channel. 3) The Channel Stde Slopes and Channel Bottom Width for Trapezoidal Channels. 4) The Channel Diameter for Circular Channels. Each of these items !s described !n connection with the Normal Depth procedure eazller in this manual. m 1989 Dotlson & Associates. Inc.. 5629 FM 1960 West. Suite 314, Houston. Texos 77069. (713) 4403787. All Rlehts Reserved