Fluid–Structure Interaction Analysis of Ascendable Horizontal-Bar Wastewater Screen for Enhanced Trapping Performance

Wastewater accumulates debris as it moves through sewage systems and must undergo purification at treatment plants, where insoluble debris is screened at the inlet. Previous studies have focused on screening mechanisms using rotating or ascendible sub-screens with vertical bars, and the effects of horizontal bars on structural integrity and fluid flow have not yet been explored. The present study addresses this gap by proposing a novel screening mechanism with horizontal bars and providing insights into flow behaviour and structural performance. The proposed mechanism consists of a main screen, an ascendible sub-screen and a rake system, and its effects on the flow distribution inside the channel and the resulting deformations and stress affecting the mechanism are computationally analysed. The problem is modelled as a fluid–structure interaction and solved using the arbitrary Lagrangian–Eulerian approach. Velocity distribution, structural deformation and stress are analysed for the various inlet flow velocities and critical configurations of the screening mechanism. The sub-screen in the proposed mechanism exhibited reduced deformation (0.9 mm for vertical bars and 0.2 mm for horizontal bars versus 2.2 mm in previous vertical-only designs). The maximum von Mises stress values were well below the 250 MPa yield strength, with peak stresses of 3.8 MPa in the sub-screen and 0.23 MPa in the main screen. Key operating conditions causing flow separation and velocity fluctuations are identified, and design improvements are suggested. The study provides guidelines for manufacturing and operating wastewater-screening mechanisms whilst mitigating undesirable performance and minimising deformation and stress in the mechanism.