TITLE:
Numerical Investigation of Turbulent Flow through Rectangular and Biconvex Shaped Trash Racks
AUTHORS:
Hans O. Åkerstedt, Sebastian Eller, T. Staffan Lundström
KEYWORDS:
Trash Racks, Head Loss, Turbulence, CFD, Hydropower, Fish Migration
JOURNAL NAME:
Engineering,
Vol.9 No.5,
May
27,
2017
ABSTRACT: Turbulent flow through a trash rack of bars of rectangular and biconvex shapes is considered. A trash rack is composed of an array of bars fitted into a hydro-electric power station to prevent debris and fish to enter the waterway towards the turbine. The work is directed towards modeling a large number of bars for which the flow turn out to have a periodic structure. It is here shown that this case can be simplified with the flow past a single bar together with periodic boundary conditions. Using this approach the head loss is derived for different angles of attack α and blockages P for two shapes of the rack, a rectangular bar and an aerodynamically shaped biconvex bar. It is found that overall loss of the biconvex bars is in general about 15% of the loss for the rectangular case for small angles of attack. For large angle of attack this difference diminishes. Of interest for the biconvex bars is also a local minimum in the head loss for angles approximately greater than 20° and for a blockage P around 0.35. This combination of parameters gives a low loss together with an efficient barrier for debris and fishes.