Three-Dimensional porous media as a novel approach for stilling basin optimization: An experimental comparison with solid elements

Objective: The purpose of this research is to experimentally investigate and compare the effects of solid and porous baffle blocks and roughness elements on hydraulic jump characteristics downstream of an ogee spillway, aiming to optimize stilling basin design for reduced length and enhanced energy dissipation. Method: Experiments were conducted in a ۱۰ m horizontal flume with an ogee spillway, testing various arrangements of solid (impermeable) and porous (permeable, Φ=۰.۲۵) cubic blocks (۲.۱ cm) as baffle blocks and bed roughness. Five discharges (۵–۱۷ L/s) corresponding to Froude numbers (Fr₁=۴.۵۸–۵.۷۵) were used, measuring sequent depths (y₁, y₂) and jump length (Lⱼ) with a point gauge and visual grid. A total of ۱۵۷ runs compared configurations against a smooth-bed control. Baffle Block Configurations: Single-Row (full-width bar, double-block with central gap, triple-block with two gaps); Double-Row (two rows spaced ۲.۱ cm apart); Stepped Co-Flow (downstream row twice the height of upstream); Stepped Opposing-Flow (upstream row twice the height of downstream). Bed Roughness Configurations: Row-wise (transverse rows spaced ۲.۱ cm or ۶ cm); Staggered (checkerboard/offset pattern); Zigzag (dense interlocking pattern); Combined Roughness (alternating rows of solid and porous cubes). Results: All configurations reduced sequent depth ratio (y₂/y₁) and jump length (Lⱼ) compared to the classical jump. Porous elements outperformed solid ones: porous baffle blocks achieved ۱۶–۴۳% Lⱼ reduction (vs. ۱۲–۲۹% for solid), and porous roughness ۷–۴۷% (vs. ۵–۳۵% for solid). Optimal setups included double-row porous baffles, zigzag porous roughness, and row-wise (۶ cm spacing) porous/combined roughness. Porous media enhanced energy dissipation via internal shear, jet interactions, and turbulence, leading to up to ۳۶% shorter relative jump length (Lⱼ/y₂) than USBR standards. Conclusions: Porous appurtenances provide a superior, novel approach for stilling basin optimization, enabling more compact, cost-effective designs through volumetric energy dissipation mechanisms beyond form drag.

کلیدواژه ها:

Hydraulic jump ، Stilling basin ، Energy dissipation ، Porous media ، Ogee spillway