Baffle Blocks Research Articles

Dissipation of Hydraulic Energy in Stilling Basin by Cutting Baffle Blocks

This study was undertaken to evaluate the hydraulic performance of stilling basin with unusual shapes of baffle blocks. Seven groups of baffle blocks were selected for this purpose , these blocks were cut within a different forms, three of these groups were cut with angle (15º, 30º, 45º) horizontally. Another three groups were cut with the same above angles, but vertically. The seventh group was cut with semi-cylindrical section (shown from side view). For a comparison, standard trapezoidal baffle blocks were used.Dimensional analysis technique was used to obtain the dimensionless parameters of hydraulic performance of the cutting baffle blocks and the drag force applied on these blocks. Laboratory experiments were carried out on one raw of the cutting baffle blocks for each model. The results indicated that the cutting baffle blocks are generally better than the standard blocks in dissipation of a hydraulic energy and reduction of a hydraulic jump length, but a ratio of drag force applied on cutting baffle blocks was greater than this ratio on the standard blocks. For the same flow conditions and angle of cut, the baffle blocks of vertically cutting gave a better results for energy dissipation and reduction in the length of the hydraulic jump than the baffle blocks of horizontally cutting, but the drag force applied on the baffle blocks with a vertically cutting was greater than applied on a blocks with horizontally cutting. Also, the results indicated that an agreement in the hydraulic performance between the baffle blocks which were cut at (45º) vertically and the baffle blocks of semi-cylindrical cutting. The cutting baffle blocks gives a greater value of the energy dissipation which was (80.62%) than the standard blocks and greater value of reduction in the hydraulic jump length which was(37.5%),also these blocks gives maximum increase of the drag force ratio which was (97%) greater than its value on the standard baffle blocks.

Development of Efficient Stilling Basins for Pipe Outlets

The results of experimental work leading to the development of shorter and improved stilling basins for pipe outlets are reported. The original USBR impact type VI stilling basin incorporates a floor that is depressed below the invert elevation of the pipe outlet. In the present study, efforts are made to develop an efficient stilling basin keeping the floor at the invert elevation of the pipe outlet. Experiments were conducted for two pipe diameters with Froude numbers ranging from 1.70 to 5.50. The new models were developed by conducting systematic experiments on a large number of stilling basins with different configurations of the appurtenances such as the splitter block, impact wall, baffle blocks, and end sill in terms of their shapes, sizes, and locations. A performance number has been defined to compare the performances of various stilling basins using a constant experimental running time and same erodible material for each model. The shapes and sizes of various appurtenances and corresponding performance results are presented. The performance of the newly developed efficient and economical stilling basins are compared with the performance of the USBR impact type VI stilling basins for pipe outlets within the range of the Froude numbers tested.

Flow Characteristics of Forced Hydraulic Jump on Two Row Baffle Blocks

Flow Characteristics of Forced Hydraulic Jump on Two Row Baffle Blocks

Radial flow stilling basins with baffle blocks

A total of 120 tests of forced radial flow hydraulic jumps have been analyzed in order to develop curves and equations for the design of radial stilling basins. The jump depth, the water surface profile, wave amplitudes, the allowable flare angle, and the jump length are defined in terms of entrance conditions, the baffle position, and the baffle height. An example design is given and compared with a USBR (U.S. Bureau of Reclamation) Type III stilling basin. Key words: forced hydraulic jump, radial flow, design, stilling basins, baffles, radial hydraulic jump, circular hydraulic jump.

Characteristics of the drag on baffle blocks

Characteristics of the drag on baffle blocks

Drag on Baffle Walls in Hydraulic Jump

The drag force experienced by a two-dimensional baffle wall at different locations in a forced hydraulic jump has been measured. Both the average and fluctuating components of this force have been obtained using a drag frame with strain gages as the transducing element. A force coefficient using the free jump sequent depth pressure force has been used to correlate the drag force with the relevant parameters. The drag fluctuations have been analyzed using the root-mean-square value of the fluctuations as they are found to follow a normal distribution. A unified plot for the average drag force coefficient has been obtained using the data collected and some data available in literature. Results obtained have been compared with similar results available for three-dimensional baffle blocks.

Stilling Basin Design for Low Froude Number

Laboratory tests were conducted to investigate the possibilities of increasing the energy loss and shortening the required stilling basin length for the Froude number range of 2.5 - 4.5. Data were collected for both the ordinary hydraulic jump and the forced hydraulic jump. Jumps were forced to form by the addition of appurtenances, such as baffle blocks and an end sill. A set of appurtenances and geometrical arrangements was found to perform satisfactorily. Comparison of the test data for the forced hydraulic jump with the data from an ordinary hydraulic jump for the same Froude number shows that the energy loss can be increased, the required downstream depth of water can be about 5% less than the sequent depth, and the jump can be formed in a much shorter basin.

Emergency Redesign of Silver Jack Spillway

A massive landslide destroyed the nearly completed spillway stilling basin at Silver Jack Dam in Colorado. Geologic conditions at the site, the extent of the slide, subsequent damage, and the emergency redesign of the spillway are described. Also described are the hydraulic model studies performed to assure satisfactory flow conditions and with unsymmetrical approach flow resulting from a circular curve in the approach conduit. A deflector vane was installed in the crown of the tunnel downstream from the curve to prevent the flow crossing over the top and sealing the portal. Vanes were developed for the stilling basin approach chute to improve flow distribution in the basin. Unique baffle blocks were developed to provide good energy distribution in a basin that had insufficient tailwater depth to form a conventional hydraulic jump. Pressure measurements were made on the conduit bend, conduit vane, chute vanes, and baffle blocks.

REGIMES OF FORCED HYDRAULIC JUMP

ABSTRACT Presented herein is a detailed description of the various types of forced hydraulic jumps formed with the assistance of baffle walls and baffle blocks. Methods of possible analysis and further research required to understand these flow configurations have been discussed.

Discussion of “Drag Forces on Baffle Blocks in Hydraulic Jumps”

Discussion of “Drag Forces on Baffle Blocks in Hydraulic Jumps”

Discussion of “Drag Forces on Baffle Blocks in Hydraulic Jumps”

Discussion of “Drag Forces on Baffle Blocks in Hydraulic Jumps”

Drag Forces on Baffle Blocks in Hydraulic Jumps

Large bluff-shaped objects (baffle blocks) placed in the jump improve the hydraulic jump performance characteristics. Knowledge of the drag force on the blocks would aid in determining the optimum block geometry. The highly turbulent and nonuniform flow in the jump prevent a theoretical solution to the problem. An experimental technique similar to that employed by aerodynamicists was used to directly measure the drag forces. Block location, height, width, spacing, second-row location, and shape were the geometrical variables investigated. The study was limited to nonsubmerged jumps in wide, rectangular, horizontal channels. A drag force ratio using the free jump, sequent depth pressure force proved more practical for data correlation than a classical drag coefficient. Resultant downstream water depths computed using the measured drag force compared favorably with experimentally measured values. The results enable the designer to calculate the drag force for a wide range of block geometries and jump inlet Froude numbers from 3 to 10.