M.h. Omid, M.esmaeeli Varaki,
Volume 9, Issue 2 (7-2005)
Abstract
خTo reduce the construction costs of stilling basins of hydraulic jump type is sometimes, novel geometries are sometimes used to adopt the basin to the upstream and downstream sections without any transition structures. Otherwise, any changes in the geometry of the basin would cause changes in the conditions and characteristics of the hydraulic jump. In this study, the effects of variation in both the side slopes and the diverging angle of a gradually expanding stilling basin with trapezoidal section on the jump condition were experimentally investigated. The experimental tests were conducted in a specially designed model for a wide range of side slopes and longitudinal divergences of the basin walls. The important parameters of the jump, such as the length, sequent depth and the rate of energy loss were computed and compared to those in the normal jumps. Tests were conducted for three different side slopes (0.5:1, 1:1, 1.5:1) and four diverging angle (3o , 5 o, 7o, 9o) with the straight jump in the rectangular section and in the wide scope of decsent numbers (from 3 to 9). The results indicate that any decrease in the side wall slopes for a particular angle of divergence would cause a reduction in the sequent depth and an increase in the jump length and energy loss compared to the rectangular section on the same angle of divergence. It is also found that the longitudinal divergence of the side walls for a particular side slope will increase the stability of the jump within the stilling basin. It will also cause a reduction in the sequent depth and the jump length as well as an increase in energy loss of the jump, when compared to the straight jumps in either rectangular or trapezoidal sections.
R. Khankhani Zorab, S. M. Kashefipour,
Volume 22, Issue 1 (6-2018)
Abstract
The purpose of this study was to evaluate two perforated sills in the stilling basin and their impact on characteristics of the hydraulic jump, such as the length of the roller of hydraulic jump, decrease in the secondary depth of the hydraulic jump, and the required tailwater depth. Also, the optimal distance of two perforated sills from the beginning of the stilling basin with a fixed height for the perforated sill and ratios of the opening of holes equal to 50% were determined. The experiments were carried out in the form of 48 tests for different discharges in the range of 47 to 145 lit/s and for Froude numbers in range of 3.6 to 11.2. The results of the experiments on two perforated sills showed that they could only reduce the length of the roller of the hydraulic jump to an acceptable level, with the distance between them providing the conditions to create a stable jump; also, the length of roller of jump was not decreased by reducing the distance between the sills. Also, they decreased the secondary depth of the forced hydraulic jump up to 27.8%, which was less than the secondary depth of the free hydraulic jump; the length of roller was up to 76.9 % less than the length of the roller of the free hydraulic jump for the Froude number of 11.2.
Z. Eshkou, A. Dehghani, A. Ahmadi,
Volume 23, Issue 3 (12-2019)
Abstract
Stilling basins have been used as an energy dissipater downstream of hydraulic structures. Dimensions of the stilling basins depends on hydraulic jump characteristics. In this research diverging hydraulic jump with an adverse slope using baffle blocks and an end sill have been studied experimentally and effect of diverging angle of the walls, adverse bed slope and baffle blocks on the hydraulic jump characteristics have been evaluated. Tests have been done for rectangular stilling basin with different bed slopes (0.025-0.05-0.075) and different diverging angle (3-5-9) degree and using baffle blocks. Discharge and Froude numbers considered to range from 39 to 81.7 lit/s and 4.44 to 8.56 respectively. Results have been indicated that the baffle blocks have been reduced sequent depth ratio and relative length of the jump 12% and 18% respectively (in comparison to diverging stilling basin with adverse slope without block). It was also found that baffle blocks and end sill could considerably improve the general condition and features of an expanding hydraulic jump with an adverse slope and could stabilize the position of this type and bi-stable situation of the flow.
