A slip condition was implemented on the side walls and the bottom wall of the computational domain.
A pump shaft, a grid and other parts inside the duct were correctly modeled in mesh generation.
4. Comparison of Experimental and Computational results
4.1 Intake Duct Pressure Loss
Fig.5 to Fig.10 depict the pressure loss at various I.V.R. Since the intake duct was designed at (I.V.R.)n = 1.0, the minimum loss can be observed around this design point in each case. Computational results are available at (I.V.R.)n = 1.0 and (I.V.R.)n = 3.0.
4.1.1 Effect of Grid Existence
Fig.5 and Fig.6 show the pressure loss coefficient ζ for "flat and flat" and "flat and tapered" intake combinations with and without grid, respectively. In spite of the existence of a grid, the loss coefficient becomes almost the same at (I.V.R.)n = 1.0. On the other hand, the difference between experimental and computational results becomes larger at (I.V.R.)n = 3.0, and in both figures, the computational results with a grid show larger loss than the experimental ones. However, the computational results without grid show smaller loss (Fig.5) for the flat intake and even loss (Fig.6) for the tapered intake. It might be said that the computational results overestimate the effect of grid existence.
4.1.2 Effect of Operation and Intake Duct Shape
In order to investigate the effect of two- and single-intake operation and the intake duct shape (flat or tapered), Fig.7 and Fig.8 are shown. Fig.8 depicts the loss at the single-intake operation, and CFD results predict slightly lower loss for the flat intake, although the experimental results show slightly lower loss for the tapered intake. The different tendency in the case of pressure loss without a grid can be observed.