Laserfiche WebLink
<br />4. FRICTION LOSS EVALUATION <br /> <br />Friction loss is evaluated in HEC-2 as the product of Sf' and <br />L, where Sf is the representative friction slope for a reach and L <br />is defined with equation (3). Alternative expressions for Sf avail- <br />able in HEC-2 are as follows: <br /> <br />Average Conveyance Equation <br /> <br />Sf = <br /> <br />Ql + Q2 2 <br />( K + K ) <br />1 2 <br /> <br />(6) <br /> <br />Average Friction Slope Equation <br /> <br />S = <br />f <br /> <br />Sf + Sf <br />1 2 <br />2 <br /> <br />(7) <br /> <br />(8) <br /> <br />Sf = <br /> <br />2 Sf <br />1 <br />Sf <br />1 <br /> <br />. S <br />f2 <br />+ Sf <br />2 <br /> <br />(9) <br /> <br />Equation (6), which has been used in HEC-2 since 1971, is the 'default' <br />equation used by the program; that is, it is used automatically unless <br />use of a different equation is requested by input. The program also <br />contains an option by which one of the above equations is automatically <br />selected on a reach by reach basis depending on flow regime and profile <br />type (e.g., Sl, Ml, etc.). Further discussion of the alternative methods <br />for evaluating friction loss is contained in Chapter 4, Optional Capabil- <br />ities. <br /> <br />6 <br />