Directional dependency of flow resistance in an unlined rock blasted hydropower tunnel

The dependency of the friction factor on flow direction was investigated experimentally in a milled scale model an unlined rock blasted tunnel under pressurized conditions by reversing direction. experimental data were used to highlight significance anisotropic roughness structures and variations cross-sectional area resistance. It is hypothesized that local sudden expansions area, which are followed gradual contractions, contribute significantly directional due potential separation. For reversed case, i.e. when large-scale contractions expansions, 15% lower factors observed. results also these topographical features, from driving direction, show need for development methods can be parameterize hydraulic factors.