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<br />2-77 <br /> <br />SUBPROGRAM BWEIR. COMBINATION OF WEIR <br />FLOW AND ORIFICE (OR LOW) FLOW <br /> <br />START <br /> <br />CALCULATE DISCHARGE UNDER BRIDGE BY <br />ORIFICE EQUATIO" <br /> <br />MAKE INITIAL ESTIMATE OF ENERGY ELEVATION <br /> <br />1970-2005 <br /> <br />2lilO <br /> <br />2125 <br /> <br />IS FLOW A COMBINATION OF WEIR AND ORIFICE <br />YES AND NOT WEIR AND LOW FLOW! <br /> <br />NO 2020 <br /> <br />INITIALIZE WEIR FLOW 1"0 ZERO <br /> <br />CALCULATE HEAD, WEIR LENGTH FOR FIRST <br />ROADWAY SEGMENT WHICH IS BELOW THE <br />ASSIlMED ENERGY ELEVATION <br /> <br />MAKE INITIAL ESTIMATE OF DISCHARGE <br />PASSING UNDER BRIDGE (CHANNEL Q) <br /> <br />2030 <br /> <br />2130-2150 <br /> <br />2165 <br /> <br />CALCULATE DOWNSTREAM VELOCITY HEAD <br />USING ASSUMED CHANNEL Q AND <br />PREVIOUS AREA <br /> <br />CALCULATE SUBMERGENCE WEIR COEFFICIENt <br />FOR ROADWAY SEGMENT <br /> <br />CALCULATE DISCHARGE OVER WEIR SEGMENT <br />AND ADD TO PREVIOUS WEIR DISCHARGES <br /> <br />CALCULATE UPSTREAM WATER ELEVATION <br />BASED ON YARNELL'S ENERGY EQUATION <br /> <br />2195 <br /> <br />CALCULATE UPSTRLAM VELoer TY HEAD <br />FROM ASSUMED ENERGY AND CALCULATED <br />WATER SURFACE ELEVATION <br /> <br />PROCEED TO NEXT ROADWAY SEGMENT <br /> <br />2215 <br /> <br />INCREASE ENERGY ELEVATION TO .1 FT <br />ABOVE UPSTREAM WATER SURFACE IF <br />VELOCITY HEAD WAS NEGATIVE <br /> <br />IS END OF ROADWAY SEGMENT ABOVE ASSUMED YES <br />ENERGY ELEVATION? <br /> <br />NO <br /> <br />2220 <br /> <br />2230 <br /> <br />CALCULATE UPSTREAM: <br />VELOCITY FROM VELOCITY HEAD. <br />AREA FROM DEPTH. <br />DISCHARGE FROM AREA AND VELOCITY <br /> <br />CALCULATE HEAD AND WEIR LENGTH FOR <br />SEGMENT OF ROADWAY <br /> <br />ARE ANY OF REMAINING ROA~'AY ELEVATIONS <br />BELOW ASSUMED ENERGY ELEVATION? <br /> <br />YES <br /> <br />2240 NO <br /> <br />YES <br /> <br />ARE ASSUMED AND COMPUTED CHANNEL Q <br />WITHIN ONE PERCENT? <br />NO <br /> <br />CALCULATE NEW STARTING HEAD AND WEIR <br />LENGTH <br /> <br />2265 <br /> <br />MAKE NEW ASSUMPTION OF CHANNEL Q <br /> <br />2085 <br /> <br />ADD DISCHARGES FOR WEIR AND ORIFICE (OR <br />LOW FLOW) TO OBTAIN COM:F'UTED DISCHARGE <br />FOR ASSUMED ENERGY ELEVATION <br /> <br />YES IS COMPlITED DISCHARGE WITHIN ONE PERCENT <br />OF ACTUAL DISCHARGE! <br /> <br />NO <br /> <br />2280 <br /> <br />MAKE NEW ASSUMPTION OF E~~RGY ELEVATION <br />2315-2350 <br /> <br />NO <br /> <br />CALCULATE MAXIMUM El'.'ERGY ELEVATION FOR <br />LOW FLOW ASSUMING CRITICAL DEPTH AT LOW <br />CHORD ELEVATION <br /> <br />FOR ASSUMED TYPE OF FLOW UNDER BRIDGE <br />IS FINAL ENERGY ELEVATION CO:1PATlBLE? <br /> <br />IF NOT ASSUME OPPOSITE TYPE OF FLOW <br />UhllER BRIDGE <br /> <br />YES <br /> <br />ACCEPT ENERGY ELEVATION, SOLVE FOR COR- <br />RECT WATER SURFACE ELEVATION IN MAIN <br />PROGRAM <br /> <br /> <br />Figure 5 <br /> <br />2370 <br /> <br />12 <br />