Characteristics of Submerged Flow Below Gate With Sill in Non-Prismatic Channels
The characteristics of submerged flow below vertical gate with sill upstream of horizontal diverging channel reach are analyzed based on experimental investigation. The experimental program is conducted in a laboratory flume with 10 cm wide, 31 cm deep and 3.0 m long. A diverging channel reach with fixed length and constant divergence angle is used. Polygonal sills with constant height, constant upstream slope and variable downstream slope are used under the gate. These sills are tested under wide range of similar submerged flow conditions to investigate the effect of sill slope on the flow characteristics. Also, a particular sill is tested under different heights to address the effect of sill height on the flow characteristics. Both the effects of submergence and the under-gate Froude number on the flow below the gate are discussed. Different flow regimes are considered (Supercritical, critical and subcritical flow). It is found that the presence of sill under the gate upstream of diverging channel reach has a remarkable effect on the discharge coefficient of the gate. It is noticed that the submergence ratio and the upstream head ratio are not able to explain the observed variations (or scatter of data) in the discharge coefficients. These variations or scatters are completely explained by the under-gate Froude number and the differential head ratio.
EFFECT OF BAFFLE BLOCKS ON THE PERFORMANCE OF RADIAL HYDRAULIC JUMP
The effect of baffle block (sill) on a radial hydraulic jump (R.H.J.) has been investigated and analyzed, in order to derive the limiting design parameters for this type of jump in expanding channels. The limiting design conditions refer to the radial hydraulic jump, when it occurs entirely on the horizontal bed, with a sill liable to move in both horizontal and vertical directions. This study was carried out in the laboratory for Froude number ranged from 2 to 6.5 to find non-dimensional relationships between the design parameters of radial hydraulic jump for different height of local baffle blocks. Generally the obtained results showed a good fitting between the different' parameters. Also results indicated that the energy loss and the sequent depth for a radial hydraulic jump are affected by baffle blocks. INTRODUCTION Hydraulic jump is one of the classical problems in the field of applied hydraulics. It was first investigated experimentally by Bidonein in 1818. This led Belanger in 1828 to distinguish between mild (subcritical) and steep (supercritical) slopes. Hydraulic jump is frequently produced by barrier in originally uniform flow. There after abundant studies were made and the results were quoted by many Fourth International Water Technology Conference IWTC 99, Alexandria, Egypt 256 writers. Although most hydraulic jumps in stilling basins are rectangular in plan, there are several stilling basins that have diverging sidewalls. The term radial hydraulic jump refers to a jump in a stilling basin with diverging walls, i.e. radially expanding flow. The radial hydraulic jump can be controlled or affected by sills of various designs, such as sharp-crested weir, broad crested weir, and abrupt rise and drop in channel floor. The function of the sill is to ensure the formation of a jump and to control its position under all probable operating conditions. The energy loss in the radial hydraulic jump is slightly higher than the corresponding one in rectangular jump. In practice, the stilling basin is seldom designed to confine the entire length of a free hydraulic jump on the paved apron, because such a basin would be too expensive. Consequently, accessories to control the jump are usually installed in the basin. Baffles and sills are used simply as safety devices and the basin is designed to have the full, free jump sequent depth [7,8]. There are other designs for a reduced sequent depth in rectangular jump by assuming that appurtenances to dissipate a portion of the excess energy [1,6]. A few studies of diverging flow basins with baffle blocks have been reported in the literature. Moore and Meshgin in 1970 studied the use of the radial hydraulic Jump as an energy dissipator for culvert outlets, the Froude numbers in their experiments were relatively low (Fr < 3) while their flare angles were large (20<θ<60). Nettleton and McCorquodale [9] studied the effect of baffle blocks on the performance of the radial hydraulic jump. His results indicated that an end sill would improve the performance of the radial stilling basin. Therefore, in this study an attempt is made to explore design parameters for radial hydraulic jump on a horizontal slope with Fourth International Water Technology Conference IWTC 99, Alexandria, Egypt 257 affecting baffle blocks.
Numerical tools applied to power reactor noise analysis
In order to be able to calculate the space- and frequency-dependent neutron noise in real inhomogeneous systems in two-group theory, a code was developed for the calculation of the Green's function (dynamic transfer function) of such systems. This paper reports on the development as well as the test and application of the numerical tools employed. The code that was developed yields the space-dependence of the fluctuations of the neutron flux induced by fluctuating properties of the medium in the two-group diffusion approximation and in a two-dimensional representation of heterogeneous systems, for both critical systems and non-critical systems with an external source. Some applications of these tools to power reactor noise analysis are then described, including the unfolding of the parameters of the noise source from the induced neutron noise, measured at a few discrete locations throughout the core. Other concrete applications concern the study of the space-dependence of the Decay Ratio in Boiling Water Reactors, the noise-based estimation of the Moderator Temperature Coefficient of reactivity in Pressurized Water Reactors, the modeling of the beam- and shell-mode core-barrel vibrations in Pressurized Water Reactors, and the investigation of the validity of the point-kinetic approximation in subcritical systems driven by an external source. In most of these applications, calculations performed using the code are compared with at-power plant measurements. Power reactor noise analysis applications of the above type, i.e. core monitoring without disturbing plant operation, is of particular interest in the framework of the extensive program of power uprates worldwide.