April 26th 2012 Kongsberg Padleklubb signed an agreement with Northwest Hydraulic Consultants, Edmonton, Canada on the Modelling phase of the Nybrufossen Whitewater Park. The modelling report is scheduled for July 6th, to be an important part of the city plan to be presented to the town committees for the approval processes.
Work started on May 1st, and the framework is already taking shape. These days NHC and KPK are working on transferring survey data to a contour map showing the bathymetry (river bottom) in detail.
Phase Objectives: The main objective of the physical model study will be to create an advanced playwave feature on the Numedalslaagen River by restructuring the ledge at the downstream end of the upper pool. The physical model will be used to evaluate playwave performance over a desired range of target river discharges (40 m3/s to 140 m3/s) and, if necessary, to mitigate any hydraulic issues resulting from the proposed modifications.
Model Scale and Similitude: Scale hydraulic models require that the force relationships in the model and prototype are dynamically similar. To achieve this similarity inertial to gravity, pressure, viscous and surface tension forces must be the same
between model and prototype; only a 1:1 scale model can achieve these criteria. Modelling at a reduced scale involves identifying the primary force relationship to accurately simulate prototype conditions, then selecting a model scale to minimize any scale effects. For free‐surface flow conditions, such as those being simulated for the Nybrufossen Whitewater Park Project, inertial and gravitational forces are the dominant forces that define the hydrodynamic flow conditions.
Model Description: As shown in Figure 1, the 1:12 scale model will encompass the main channel width through the falls section and a significant portion of the lower pool extending downstream to the Numedalsveien Bridge. At the selected scale, the model will reproduce a 170 m long reach of the Numedalslaagen River at the falls section with prototype channel widths of 60 m at its upstream extents and 100 m at the downstream boundary. The red, dashed line in Figure 1 represents the actual location of the upstream model boundary; the area upstream of this line will be used in the model to properly simulate flow conditions entering the upper pool from both the vertical ledge and the chute adjacent to the rock outcrop.