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<br />For a subcritical profile, a preliminary check for proper flow <br />regime involves the following equation: <br /> <br />(*) <br /> <br />test <br /> <br />= At <br />21 <br /> <br />(10) <br /> <br />where: <br /> <br />( %) <br /> <br />test <br /> <br />= velocity head that would exist if critical <br />conditions existed at the balanced water <br />surface elevation and a = 1. <br /> <br />At <br />T <br /> <br />= total flow area <br /> <br />= water surface width <br /> <br />v2 ( V2 ) <br />If the calculated velocity head, a~, is less than 94% of ~ test <br />the balanced water surface elevation will be accepted for the cross <br />section. If the calculated velocity head is greater than 94% of the <br />test value, the critical water surface elevation will be determined <br />(by a procedure discussed in section 6) so that a direct comparison of <br />balanced elevation versus critical elevation can be made. <br /> <br />For a supercritical profile, critical depth is automatically <br />calculated for every cross section, which enables a direct comparison <br />between balanced and critical elevations. <br /> <br />6. CRITICAL DEPTH DETERMINATION <br /> <br />Criti ca 1 depth for a cross secti on wi 11 be determi ned if any of <br />the following conditions are satisfied: <br /> <br />(1) The supercritical flow regime has been specified. <br /> <br />(2) Calculation of critical depth has been requested with the <br />program's critical depth option. <br /> <br />(3) This is the first cross section and critical depth starting <br />conditions have been specified. <br /> <br />(4) The critical depth check for a subcritical profile indicates <br />that critical depth needs to be determined to verify the flow <br />regime associated with the balanced elevation. <br /> <br />The total energy head for a cross section is defined by: <br /> <br />H = <br /> <br />WS + <br /> <br />aV2 <br />2g <br /> <br />(11 ) <br /> <br />8 <br />