## 5 Conclusions  
This study systematically investigates the drag reduction and efficiency enhancement mechanisms of dimpled non-smooth surface structures in wide-range electric submersible centrifugal pumps through bioinspired structural optimization. Key findings are summarized as follows:  
1. The dimpled non-smooth structure effectively suppresses boundary layer separation near the impeller wall and reduces viscous friction losses. Numerical simulations indicate that the optimized impeller (dimple diameter d = 0.9 mm) achieves 12.98%and 8.55% improvements in head and efficiency, respectively, compared to the baseline impeller at 150 m\({}^{3}\)/d. Experimental validation confirms an 11.5% head gain and a 4.6-percentage-point peak efficiency enhancement at 130 m\({}^{3}\)/d.
2. Dimple diameter exhibits a nonlinear correlation with performance gains, with d = 0.9 mm yielding optimal overall performance. The structural arrangement significantly impacts drag reduction, where dimple arrays on the trailing edge of the pressure side maximize efficiency by regulating shear layer instability.
3. Experimental and simulated head-flow curves align in trend, but experimental head values are systematically 1.2-2.8% higher, with a 4% efficiency deviation at 150 m\({}^{3}\)/d. These systematic errors arise from the combined effects of anisotropic wall roughness, multiphase flow interface slip, and additive manufacturing micro-defects.
4. The single-region optimization strategy (dimples on the pressure side trailing edge) achieves over 90% of the total performance improvement while maintaining high manufacturability, offering a practical solution for dynamic adaptability of wide-range pumps and intelligent well completion technologies.  
Future work should focus on long-term wear characterization of non-smooth structures in multiphase flows and the development of machine learning-based algorithms for multi-parameter co-optimization to enhance adaptive performance under complex operating conditions. Additionally, integrating real-time monitoring technologies will accelerate the engineering application of bioinspired drag-reduction structures in intelligent oil recovery systems.  
Conceptualization, T.F. and S.W.; methodology, S.W.; software, T.F.; validation, T.F., S.W. and Y.G.; formal analysis, T.F. and B.S.; writing--original draft preparation, T.F.; writing--review and editing, B.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Youth Innovation Project Fund (2022-4020-000158-KTY), Research Institute of Petroleum Exploration and Development, PetroChina Company Limited.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
Special thanks to RIPED's Research Department for providing critical infrastructure access and technical coordination, enabling efficient progress at key project stages.  
Authors [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company PetroChina Company Limited. All of the authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The sponsors had no role in the design, execution, interpretation, or writing of the study.