Screen-Type Energy Dissipator for Hydraulic Structures

Laboratory experiments have shown that screens or porous baffles with a porosity of about 40% could be used as effective energy dissipators below small hydraulic structures, either in a single wall or a double wall mode. The experiments were carried out for a range of supercritical Froude numbers F₁ from about 4 to 13, and the relative energy dissipation was appreciably larger than that produced by the corresponding classical hydraulic jumps. These screens or porous baffles produced free hydraulic jumps, forced hydraulic jumps, and in some cases submerged jumps. The flow leaving these screens was found to be supercritical with a Froude number approximately equal to 1.65 and a tailwater depth equal to 0.28 times the subcritical sequent depth ${\mathit{y}}_{\mathit{2}\mathit{*}}$ of the classical hydraulic jump with the same F₁. To produce a secondary jump downstream of the screens, the tailwater depth needed was found to be about one half of ${\mathit{y}}_{\mathit{2}\mathit{*}}$.