Local similarity and velocity distribution in turbulent flows

Hydraulics and Engineering Hydrology

Justification of conditions for similarity of turbulent flows cinematic and dynamic characteristics is fundamental for solving the hydraulic modeling problems and calculating the water supply and sewerage systems, culverts in hydraulic and highway engineering. In the article the local kinematic similarity conditions for turbulent pipe flows were investigated. It was established that Prandtl-Nikuradze similarity conditions were not universal for various hydraulic resistance regimes and wall velocity distribution had not any theoretical foundation. The analysis of local similarity flows principal Von Karman- Sedov was presented. It was showed that logarithmic and wall law velocity distribution in equal measure corresponds to this principal and both dynamic velocity and drag coefficient are the similarity parameters for velocity distributions. The data of velocity measurements corresponding with logarithmic and wall law velocity distribution for rivers which distinguished by discharges and scales is presented. Two investigated methods for dynamic velocity determination with using logarithmic and wall law velocity profiles were described. It was indicated that this two different determination methods displayed equivalent dynamic velocities for each investigated river flow.