Optimization of rectification bottom sill parameters in drainage pumping stations

Adverse flow patterns, such as backflow and vortex, often exist in the intake structure of drainage pumping station, which affected the stability of pump operation. Many rectification measures have been proposed to improve the flow patterns, one of which is the bottom sill. This study aims to optimize the design for the shape and layout of bottom sill using computational fluid dynamics (CFD) technology and response surface method (RSM), where the height and distance parameters were most important influence factors. Taking the height and distance as design variables, a systematic optimization was performed on the structural parameters of bottom sill to improve flow patterns. A comparison was made on the numerical calculation and model test results on surface streamlines and velocity distribution, thereby to verify the reliability of numerical simulation used in this study. A Sobol' index method was utilized to clarify the global sensitivity of response surface model, together with the interaction between design parameters. Furthermore, the information weight method was used to estimate three evaluation indexes: the coefficient of hydraulic loss, unevenness coefficient of flow rate, and characteristic value of horn mouth vorticity, in order to form a comprehensive objective function. As such, the comprehensive objective function quantitatively showed the influence of bottom sill rectification on the velocity and vorticity field in the intake structure of drainage pumping station. The results showed that the changes of two design parameters had a great influence on the response surface model, indicating that there was a significant interaction between the height and distance parameters of the bottom sill. The relative height of bottom sill had a higher impact on the model than the relative distance. There was a great impact on the flow pattern of intake structure under the coupling height and distance of bottom sill, indicating a significantly improved flow pattern after optimizing. An optimal combination of parameters was obtained using the steepest descent method in the response surface model, where the relative height of bottom sill was 0.29, and the relative distance of bottom sill was 5.02. The uneven distribution coefficient of velocity, hydraulic efficiency of computational domain, and vortex distribution value of intake bell mouth were reduced by 19.28%, 5.26% and 5.76%, respectively. In addition, the R2 for the comprehensive objective function was 0.86, and the root mean square error was 0.02. The relative error was 1.30% between the predicted value and the actual one from the calculated comprehensive objective function. The data showed that the response surface model can accurately optimize the relationship between the design parameters of bottom sill and the comprehensive objective function. The information weight method can be used for the multi-objective optimization on hydraulic characteristics of intake structure. The response surface model can be applied to the parameter optimization of rectification measures in pumping station.