Study on the Best Depth of Stilling Basin with Shallow-Water Cushion

Abstract

The depth of the stilling basin with shallow-water cushion (SBSWC) is a key factor that affects the flow regime of hydraulic jump in the basin. However, the specific depth at which the water cushion is considered as 'shallow' has not been stated clearly by far, and only conceptual description is provided. Therefore, in order to define the best depth of SBSWC and its relationship between the Froude number at the inlet of the stilling basin, a large number of experiments were carried out to investigate SBSWC. First of all, 30 cases including five different Froude numbers and six depths were selected for which large eddy simulation (LES) was firstly verified by the experiments and then adopted to calculate the hydraulic characteristics in the stilling basin. Finally, three standards, based on the flow regime of hydraulic jump, the location of the main stream and the energy dissipation rate, were proposed to define the best depth of SBSWC. The three criteria are as follows: (1) a complete hydraulic jump occurs in the basin (2) the water cushion is about 1/10-1/3 deep of the stilling basin, and (3) the energy dissipation rate is more than 70% and the unit volume energy dissipation rate is as high as possible. It showed that the best depth ratio of SBSWC (depth to length ratio) was between 0.1 and 0.3 and it also indicated the best depth increased with the increase in Froude number. The results of the work are of significance to the design and optimizing of SBSWC.

Numerical Study of Fluctuating Pressure on Stilling Basin Slab with Sudden Lateral Enlargement and Bottom Drop

“…When jets flow into the stilling basin, there are various shapes of eddies with horizontal and vertical vortices. According to previous research [5], this study divided the center line of the stilling basin slab into three zones along the mainstream direction: underflow swirling zone (I), impinging zone (II), and wall-attached jet zone (III). Combined with Figure 4, it can be concluded that because the sluice and the bottom plate are connected by a falling drop, there is a certain thickness of water cushion in the downstream of the stilling basin.…”

“…A stilling basin with bottom drop plays an important role in a new type of energy dissipater, which is obviously different from the traditional underflow stilling basin [4]. Li et al [5] focused on the best depth of a stilling basin with shallow-water cushion by large eddy simulation (LES) modeling. Luo et al [6] studied the distribution characteristics of fluctuation pressure and lifting load in a stilling basin with step-down for floor slab.…”

“…In order to obtain the information of the entire flow field, it is particularly necessary to use a turbulence model that can reflect the fluctuation of the water flow. The large eddy simulation (LES) model has a proportional advantage in simulating the characteristics of water flow fluctuation [5,[21][22][23].…”