FLOOD06195 - Laserfiche WebLink

Home Browse Search

44 TECHNIQUES OF WATER-RESOURVES INVE&rIGATIONB Table: 6.-Oischarge coefricients for box or pipe cul....erts set flush in 0 vertical headwall with variation of head and entrance rounding or beveling; type 5 flow hl-Z r/b,w/b,rlD,orw/D D I o 0.02 0.04 0,06 0.08 I 0.10 0.14 -- - -I-- I. 4 0,44 0. 46 0,49 0. 50 O. 50 0, 51 0, 51 1.5 ,46 .49 .52 ,53 .53 ,54,54 1. 6 . 47 ' 51 . 54 ' 55 , 55 ,56 ,56 1. 7 ,48 ' 52 .55 ' 57 .57 . 57 ,57 1. 8 , 49 ' 54 . 57 ' 58 , 58 ,58 ,58 1.9 ,50 ,55 .58 ,59 .60 .60,60 2, 0 , 51 , 56 . 59 ' 60 ,61 i ,61 ,62 2,5 ,54 .59 .62 ,64 ,64 ,65.66 3, 0 ' 55 ' 61 . 64 , 66 , 67 ,69 ,70 3, 5 ' 57 ' 62 . 65 ' 67 ' 69 ,70 ,71 4. 0 ' 58 . 63 ' 66 , 68 ' 70 ,71 ,72 5. 0 ' 59 ' 64 . 67 , 69 . 71 I ,72 ,73 than 0.03 will type 5 flow occur. Even under these conditions the flow may eventually tranH- late to type 6 flow. If type 5 flow is believed to exist, the following dischar!(e coefficients are applicable: (hl-Z)/D C I (1i1-z)JD C --- --- ---- 1.4 0, 48 2,0 0,57 1.5 ,50 2,5 ,59 1.6 ,52 3,0 ,61 I 1.7 ,53 3,5 .63 1.8 ,55 4.0 .65 LI.9 ,56 5,0 i ,66 Wingwall entrance Pipe culverts set flush with vertical headwall For pipes set flush with a vertical headwall, the addition of wingwalls to the entrance does not, affect the dischar!(e coefficient, which can be determined from table 6, Box culverts Determine the discharge coefficient for box <,ulverts with wing-walls and a square top en- trnnee from llthle 7. If the top entrance is rOlludcd or heveled, Helect the coefficient from tuhl. {i on the l",siH of wiD or "ID for the top ('tltrlltlCe, bllt llse the coefficient from table 7 a:-; II lower limiting- vulue. Projecting entrance Corrugated-metal pipes and pipe-orches Def,ermine t.he dischnrge coefficient for pipe~ und pipe.n.rehes thnt. extend pnst n helldwllll or Table 7.-Discharge coefficients for box culverts with wing_ W<llls with variation of head and wingwall angler 8; type 5 flow Ill-z I Wlngwall angle, f! -iJ~ I ,~ ---- 30' <s' Ol" '" 90' --I -----1- ,.-.--- ---.- ---~--~ -----.-- 1.3 0, 44 0,44 0, 43 0, 42 0,39 1.4 ,46 ,46 ,45 ,43 ,41 1.5 ,47 ,47 ,46 .45 ,42 1.6 ,49 ,49 ,48 .46 ,43 1.7 ,50 ,50 ,4R ,47 ,44 I.R ,51 ,5t ,50 ,48 ,4.5 1.9 ,52 ,52 ,5] ,49 ,46 2,0 ,53 ,53 ,52 ,49 ,46 2,5 ,56 ,56 ,54 ,52 ,49 3,0 ,58 ,58 ,56 ,54 ,50 3, 5 ,60 ,60 ,58 ,55 ,52 4, 0 ,61 ,61 ,59 .56 ,53 5,0 ,62 ,62 ,60 .58 ,54 embankment by fi",t, selecting a coefficient from table 6 and (,hen multiplyin~ by an adjust.ment, fuetor kL, Conctp.te pipe with beveled end Determine the discharge coefficient for a concrete pipe with a beveled end directly from table 6, Mitered pipe set flush with slaping embankment Determine the discharge coefficient for mi- tered pipes set flush with a sloping embank- ment by first selecting a coefficient from table 6 for a square-ended pipe and then multiplying this coefficient by 0.92. If the mitered pipe is thin walled (such as corrugated metal) and projects beyond the embankment, the adjustment factor kL should be applied also. Unusual culvert entrances The coefficient of discharge for the commer- cial flared opening described in figure 8 is 0,95 for flow types 1, 2, and 3 for all diam- eters of pipe and all values of (h,-z)ID. The properties of these flared end sections are shown in figure 8. For culvert entrances of unusual shape, estimate the discharge coefficient on the basis of known values for the more common shapes (reentrant, sharp, 45-de!(ree wingwalls), For the six types of flow discussed in this manual, this entrance coefficient can usually be esti- mated with sufficient accuracy, In high-head flow the entrance shape is very i;"portant e -e -e