Flow Characteristics around and Upstream of Different Outlets Arrays in a Reservoir

Reservoirs as an essential part of the hidroelectrics projects around the world, determines almost in every case their lifespam. One of the main problems for reservoirs are the sediments and it's deposition on the lake bottom therefore reducing the water availability. a widely used technique worlwide is the venting of the sediments while they are still suspended, this alternative interact with the enviroment downstream and upstream, that is why is important to study it's effects on fish communities, alteration of the side slopes, and effectiveness on sediments removal.

The present study intends to visualice through a physical model in the laboratory the effects of different arrays of circular intakes with the same diameter (D=Z.5cm), in the flow characteristics upstream of a dam and its influence on sediment transport. The reservoir is represented by an acrylic tank with 10m long, s0D high and Z0D wide, the given dimensions and energy dissipers are provided in order to avoid the effects of the inflow in the measurements, ensuring that the only effect captured with the acoustic doppler velocimeter is from the outlets. The result will be then compared with a simulation done on the €FD software Flow sD, the software uses a finnite differences method to better represent hidraulic problems with free surface. The experimental procedure is also done on a stratified water body, a typical characteristic of tropical climate reservoirs, to compare results with symilar experiments on highest latitudes.

Powell and Khan (Z014) stated that the velocity profiles (vertical and horizontal components) didn't change within the "high aceleration zone" (a distance upstream from the outlet < ZD) for a single outlet. The results obtained in the experiments with a single outlet and two outlets varying their distance from 4.5D to 9D, show that on a distance between ZD and 4D upstream, a reduction of about 80% on velocity magnitude could exist.

For a sediment current on a stratified water body, the experiments shows that the change of altitude isn't done until it reaches the wall (or any obstacle), and that the vertical component of velocity, unlike the horizontal component acording to the observed results, is only significant on a distance < ZD from the outlet, being this criteria from opening the outlets on the venting method when a intrusive density current is approaching.