3D modelling of transversal grates comparison of numerical result with experimental data

Abstract

The full scale (1:1) test platform located at the UPC (Universitat Politècnica de Catalunya) allows us to reproduce the local runoff process and the study of inlet grates or other types of capture systems. Over the last few years, several tests have been made on this platform, which has helped to determine the efficiency of each grate based on the chosen parameters, such as approaching discharge and flow depth. Prof. Gómez Valentin Manuel and Prof. Russo Beniamino proposed a new law, which would define the grate efficiency as a function of the just mentioned parameters. The goal of this study was to reproduce these tests for a specific grate (ULMA FNX 250 FTDM) with numerical code FLOW-3D which solves the RANS equation (Reynolds Average Navier Stokes Equations); this is the best method to perform such detailed analysis. The model includes the complete platform and the inlet zone, excluding all unnecessary parts, decreasing the simulation computational cost. The calibration was made comparing the results from the numerical simulation with measurements taken during the experimental tests, such as the flow depth and the captured discharge by the grate; the results were taken once the steady flow was reached. The model’s final results showed minor acceptable errors and thus guarantee the validity of the process. The analysis of the results allows us to better understand how much water is intercepted by the studied grate. This helps us determine the most adaptable process to a definite work condition; with this information it also possible to propose a new inlet-design guideline to improve its capture efficiency. In conclusion, we determined that with good meshing, good modelling and good calibration it is possible to use CFD solvers like Flow3D as an effective substitute for laboratory tests. This is because they allow extrapolating much more information on the model.