1 - Alaska Energy Data Inventory

Figure 7 in appendix B2 contains a summary of hydraulic losses along withdetailed loss calculations.Calculations were performed for maximum, expected and minimum hydrauliclosses. Expected losses were used for determining the economic tunneldiameter. Maximum losses were used to calculate minimum internal pressuresincluding minimum water hammer at the unit. Minimum losses were used tocalculate maximum internal pressures, maximum water hammer and stability ofthe surge tank.For detailed breakdowns of all losses for the different sections of thepower conduit, see figure 7 in Appendix B2. Plate Bl illustrates hydrauliclosses in various portions of the power conduit.B. Losses in the Power Conduit.(1) Unlined Tunnela Expected Losses - The unlined portion of the power conduit is anll-ft modified horseshoe tunnel as shown on Plate 4. The effectiveroughness in the unlined tunnel is expected to be approximately 4-1/2inches or 0.375 ft. The nominal tunnel area is 102.8 ft2 which resultsin a circular equivalent diameter of 11.4 ft and a relative roughness (perHOC 224-1/6) of 11.4 ft/.375 ft = 30.5. Based on this relative roughnessthe Von Karman - Prandtl roughness Equation provides a Oarcy-Weisbachfriction coefficient IIfli of 0.0585 and a Manning lin II of 0.0267, butreference 5 shows that relative roughness alone cannot fully definehydraulic resistance in unlined tunnels. Scalloping or waviness resultingfrom drilling and blasting techniques are an important factor in hydraulicresistance. Therefore, Manning's lin II was based primarily on empiricalfindings at existing tunnels summarized in HOC chart 224-1/5. Afterconsideration of 12 tunnels ranging in design cross-sectional areas from 54ft2 to 183 ft2 (nominal tunnel cross-sectional area at Crater Lake is102.8 ft2) an initial value of lin II = 0.0315 was chosen for expectedBl-15