Laserfiche WebLink
<br />15 <br /> <br />where <br /> <br />a - velocity distribution coefficient <br /> <br />. <br /> <br />d depth <br /> <br />. <br /> <br />z = bed elevation <br /> <br />Friction loss is computed from Mannings equation and "other <br /> <br />losses" include expansion losses. <br /> <br />Variables with the higher-valued subscript indicate the section under <br /> <br />, <br /> <br />solution. Friction loss is computed as follows: <br /> <br />Friction head <br /> <br />= S = ( Qn . )2 <br />f 1. 486AR2' j <br /> <br />where <br /> <br />Q <br /> <br />discharge <br /> <br />. <br /> <br />n = Manning's roughness coefficient <br />A = hydraulic area <br />R = hydraulic radius <br /> Sfi + Sfa <br />Friction loss in the reach = hf = L ( 2 ) <br /> <br />. <br /> <br />where <br /> <br />L = length of reach. <br /> <br />With z 2 known, the quantities V 2 and d2 are solved for by a trial <br /> <br />and error method. Solution then proceeds to the next adjacent section. <br /> <br />Leach's Method is used where changes in velocity head do not <br /> <br />significantly vary between stations. As in the Standard Step Method, <br /> <br />friction losses are calculated by Manning's Equation, but energy <br /> <br />balance is computed on the basis of depth and elevation heads only, <br /> <br />velOCity being assumed constant. <br /> <br />. <br /> <br />The Corps of Engineers Methods were developed for two different <br /> <br />types of situations. Method 1 covers situations where flow travel <br /> <br />between sections is essentially equal for all segments, but considerable <br /> <br />variation across the width exists for the hydraulic characteristics of <br />