Scale effects of non-aerated flow properties over gabion stepped spillways

One of the oldest types of human-made hydraulic structures is known as a stepped spillway, and the main use of such structures is to control and monitor the flow of water over embankment dams. However, a common problem encountered by designers of these structures is how to measure the impact of scaling on the structures’ performance. This paper thus investigates the effect of scale on the Reynolds and Froude similitudes of such structures using two-dimensional numerical models developed based on Reynolds-averaged Navier-Stokes equations. Dam break conditions were selected to simulate the experiments of this study; therefore, all the essential requirements were applied to achieve model stability. The impact of scaling ratio of 1:2 in gabion stepped spillways on the location of the inception point, the velocity distribution, turbulence intensity, and pressure distribution were explored. The results were then discussed and compared with previous research which conducted over normal stepped spillways. The current study is among the first to provide guidance for the flow properties over gabion stepped spillways which could be impact significantly by the scale effects. This comparative analysis emphasised that full-scale prototype extrapolation conditions may not be feasible based on the Reynolds and Froude similitudes. The current results could be appropriate to be adopted for additional types of water flow over porous steps. Nevertheless, more comprehensive experimental tests for the properties of the water flow at the prototype scale are required.