Optimization of Trapezoidal Bottom Sills for Flow Pattern Control in Integrated Diversion Gate–pumping Station Hubs

This study investigates the system-level flow-control effect of trapezoidal bottom sills in an integrated diversion gate–pumping station hub. The relative sill height (h/H, where h is the sill height and H is the design water depth), relative streamwise placement (d/D, where d is the sill placement distance and D is the diffuser-section length), and sill width ratio (b/h, where b is the sill width) were selected as the design variables. A three-factor, five-level full-factorial computational-fluid-dynamics (CFD) experimental design was combined with entropy-weighted multi-indicator evaluation, recirculation-volume-ratio constraints, response surface methodology (RSM), engineering rounding, and CFD verification. The evaluation framework jointly considered velocity uniformity, flow-direction consistency, recirculation, and vortex intensity along the diversion basin–forebay–pump sump flow path. An entropy-weighted optimal parameter combination was first identified within the investigated design space and then rounded to an implementable engineering design with h/H = ۰.۳۵, d/D = ۰.۸۶, and b/h = ۰.۳۵. For this selected rounded design, the relative deviation between the RSM-predicted comprehensive objective value and the corresponding CFD-based value was ۶.۸۶%. Compared with the original scheme, the selected design increased forebay velocity uniformity by ۲۸.۲۲%, reduced the forebay recirculation area ratio by ۹۰.۲۵%, and improved the velocity-weighted mean flow angles at the forebay and pump sump inlet sections by ۴.۸۵% and ۲۰.۴۶%, respectively. The comprehensive vorticity indicators at the two evaluated sections decreased by ۲۰.۱۱% and ۴۸.۹۱%. The recirculation-volume ratios in the diversion basin and the C-direction gate approach channel–forebay–pump sump system decreased by ۵۰% and ۴.۸۷%, respectively. Although the local hydraulic loss coefficient of the diversion basin increased from ۷.۹۴۸ to ۲۱.۷۹۰, the hydraulic efficiency of the pumping-station section changed only slightly from ۹۶.۴% to ۹۶.۳%, indicating that the selected design did not cause a substantial pumping-station efficiency penalty. Local RSM-based screening further identified the recirculation volume ratio in the C-direction gate approach channel–forebay–pump sump system as the governing feasibility constraint and showed that increasing d/D narrows the feasible neighborhood. The proposed framework provides a quantitative basis for selecting implementable trapezoidal bottom-sill geometries for hydraulic rectification in similar integrated diversion gate–pumping station hubs.

کلیدواژه ها:

CFD simulation ، Hydraulic rectification ، Recirculation suppression ، Entropy-weighted evaluation ، Response surface methodology