The main findings of the field investigations were the exstence of the current short-circuting the lake. The current followed the right bank just below the ice. This was caused by the Coriolis force and the temperature stratification of the lake. The figures below show data from the lake. The water current is from the right to the left in the images.
Bathymetry of the lake. The blue areas have a depth of over 100 meters, while the red areas have a depth of 10 meters.
Three-dimensional hexahedral unstructured grid seen from above
The water currents were calculated by solving the fully 3D Navier-Stokes equations. The convection-diffusion equation for temperature was also solved. The horizontal density gradients from the temperature stratification were included in the Navier-Stokes equations. The results are given below:
The resulting velocity vector map close to the surface
Upstream detail of the resulting velocity vector map close to the surface
Detail of the resulting velocity vector map close to the surface, from the middle of the lake
Downstream detail of the resulting velocity vector map close to the surface
Colour map of horizontal velocities close to the surface. Red is high velocity and blue is low velocity
The velocities shows a short-circuting of the lake with a current close to the water surface following the right bank, except behind the island on the right bank in the middle of the lake. This is in good agreement with the conclusions from the field data collection.
The project is carried out in cooperation with Einar Tesaker at SINTEF Civil and Environmental Engineering and Jon Friis at Foreningen til Begnavassdragets regulering (Begna River Water Management Group).
The The Research Council of Norway partly sponsored the project.
Nils Reidar B. Olsen