Author(s): Annika Andersson; Urban Svensson

Linked Author(s): Urban Svensson

Keywords: No Keywords

Abstract: Ice formation on water intakes at hydropower plants can cause serious difficulties. Frazil ice particles may deposit on the trash rack bars and a subsequent blockage of the intake may occur. A numerical model that predicts the frazil ice accumulation pattern has been developed and it can be a useful tool to complement laboratory and field experiments. The numerical model has two main components; a hydrodynamical model that gives the flow field and a particle tra­jectory model. The flow field is determined from the basic momentum equations and a twoequation turbulence model. Wakes are developed on the sides of the square cylinder and a vor­tex street is formed downstream. The particle model is incorporated as a submodel. It calcu­lates the trajectories of the particles, the position where they strike the bar and the subsequent ice accumulation. Results presented include flow, pressure and turbulence fields around a square cylinder and ice accumulation patterns when particle size and water velocity were varied. It is shown that the ice accumulation pattern depends on the size of the deposited ice particles. Larger particles (5 mm) mainly deposited at the front part of the obstacle while the smaller ones (1 mm) depos­ited at the rear part. The effect of the first deposited ice on further ice growth was also studied. No ice particles were then allowed to deposit on 1/4 of the upstream part of the obstacle. The results indicate that the initial ice accumulation on the front part is essential for the ice accu­mulation on the rear part of the cylinder.

DOI:

Year: 1996