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.
Highlights
At present, the energy dissipation by hydraulic jump is used for downstream in many hydraulic projects [1], of which the stilling basin plays an important role in energy dissipation
If the depth is not enough, no hydraulic jump takes place in the basin, and the regime of jump gets more complete as the depth increases; for example, when the depth of stilling basin is 0 cm or 5 cm, there is no hydraulic jump in the stilling basin; when the depth of stilling basin is 10 cm, 15 cm, 20 cm, or 25 cm, there is a hydraulic jump in the stilling basin
A complete hydraulic jump occurred in the depth of 15 cm, 20 cm, and 25 cm in the stilling basin when the Froude numbers are 7.64 and 6.92
Summary
The energy dissipation by hydraulic jump is used for downstream in many hydraulic projects [1], of which the stilling basin plays an important role in energy dissipation. A series of studies on the impacts caused by inlet type, inflow angle, and low Froude number of the stilling basin with shallow-water cushion on its hydraulic characteristics were conducted [7]. The concept of a stilling basin with double shallow-water cushions is an extension of SBSWC, which has the same advantages as SBSWC, but with better hydraulic characteristics [8], lower underflow speed, and better distribution of dynamic. According to the simulation of thetoflow of hydraulic the regime of hydraulic jump, the location of the main stream and the energy dissipation rate, the location of the main stream and the energy dissipation rate, the definition or the standard of the best definition or the standard of thefinally best depth of SBSWC was proposed; the and relationship between depth of SBSWC was proposed; the relationship between.
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