Laserfiche WebLink
<br />The coefficient for friction loss (kf) can be computed from Manning's <br />equation by equating two equations for friction loss in the culvert. <br /> <br />kf <br /> <br />y2 <br />b <br />2g <br /> <br />= Sf' L <br /> <br />(7) <br /> <br />where: <br /> <br />Sf = the average friction slope <br /> <br /> <br />L = the length of the culvert <br /> <br /> <br />Manning's equation for the velocity in the culvert is rearranged to <br /> <br />define Sf: <br /> <br />Vb = 1.49 R2/3 S 112 <br />n f <br />y2n2 <br />b <br />2.22R4/3 <br /> <br />S - <br />f - <br /> <br />(8) <br /> <br />By substituting equation 8 for equation 7, the coefficient kf can <br />be defined based on culvert parameters. <br /> <br />y2n2 <br />k = b .L. <br />f 2. 22R4/3 <br /> <br />kf = 29n2L/R4/3 <br /> <br />2g <br /> <br />V2 <br />b <br /> <br />(9) <br /> <br />Typical values of the coefficients are shown below <br />Description <br /> <br />k <br /> <br />Intake <br />Intermediate piers <br />Friction (Mannings equation) <br /> <br />0.1 to 0.9 <br />0.05 <br />kf <br /> <br />XKOR = ~k + 1 <br /> <br />where: <br /> <br />English <br /> <br />kf = 2gn2L/R4/3 <br />kf = 19.6n2L/R4/3 <br /> <br />Metric <br /> <br />33 <br />