Flow characteristics of grid drop-type dissipators

The flow characteristics over vertical drops equipped with a grid roof, namely the “grid drop-type dissipator”, were investigated using model experimentation. To study the flow patterns and hydraulic characteristics, all three velocity components were measured. Moreover, a flow visualization technique was used to examine the flow structure of the falling jet through the grid roof, mixing zone, and the pool. The trends of the hydraulic and geometrical flow characteristics, the length scales of distributed/deflected jets, and aspects of the hydraulic jump in the pool were examined. The results indicate that the proposed hydraulic structure eliminates unfavorable flow conditions and forms the basis of a more effective flow control system compared with a plain vertical drop. Some 70% of the experimental data were randomly selected to calibrate the derived empirical equations. The remaining 30% of the data were used to validate these equations. Estimations compare well with the test data, indicating that the proposed empirical equations provide reliable estimates for the main flow characteristics. It is demonstrated that the dispersion/diffusion mechanism in the pool increases the velocity gradient as well as the momentum exchange and consequently, increases the energy dissipation relative to a plain vertical drop.