## 1 Introduction  
Electrical submersible pumps (ESPs) have become the core artificial lift equipment in offshore oilfield development due to their advantages of high displacement, superior efficiency, and automation capabilities [1]. Statistical data indicate that ESP systems account for 92% of production wells in China's offshore oilfields, with 98% utilizing ESP lifting technology [2]. However, conventional ESP systems face two critical technical limitations: First, their narrow, high-efficiency operating ranges struggle to adapt to dynamic reservoir variations, causing frequent deviations from design conditions that lead to impeller wear and efficiency degradation [3]. Second, fixed-parameter pump designs fail to match declining productivity during late-stage oilfield development, resulting in costly frequent pump replacements [4]. Wide-range ESP technology addresses these challenges by expanding high-efficiency operating zones, reducing pump configuration requirements by over 30% through dynamic adaptability, and has emerged as a key research direction for intelligent completion technologies [5; 6; 7; 8; 9].  
Current optimization studies for wide-range ESP hydraulic performance primarily focus on flow channel topology optimization and variable frequency control [10; 11; 12]. Notably, hydraulic losses caused by rotational effects in impeller-diffuser systems and surface friction account for 40-50% of total energy losses [13], positioning surface drag reduction as a critical breakthrough for efficiency enhancement. Bio-inspired non-smooth surface structures (e.g., dimples, riblets) have demonstrated significant drag reduction benefits across hydrodynamics applications, including ship resistance reduction [14; 15], underwater robotics [16], high-speed trains [17], and petroleum engineering [18; 19].  
Recent advances reveal promising applications of bio-inspired non-smooth structures in centrifugal pump optimization: [PERSON] et al. [20] designed mushroom-like micro-textured blades mimicking sea skater exoskeletons, reducing cavitation bubble volume by 54.75% during incipient stages. [PERSON] et al. [21] achieved a 2.5% head improvement using crab shell-inspired microsphere structures. [PERSON] et al. [22] demonstrated a 5.8% torque reduction via dimple-type non-smooth units on blade pressure surfaces through numerical simulations. A comparative study by [PERSON] [23] revealed superior drag reduction performance of dimpled surfaces over V-grooves, particularly under high-flow conditions. Parametric analyses by [PERSON] [24] identified nonlinear relationships between dimple size-spacing parameters and drag reduction effectiveness, emphasizing the need for multi-objective optimization. [PERSON] et al. [25] reported a 23% efficiency gain by strategically placing non-smooth structures in high-shear-stress regions. [PERSON] et al. [26] confirmed dimple structures as optimal among three typical non-smooth surfaces (dimples, protrusions, and wavy textures) through friction coefficient calculations.  
This study focuses on optimizing dimple-type non-smooth structures for wide-range ESPs under low-flow and complex media conditions, incorporating manufacturing feasibility constraints. A CFD-based multiphysics-coupled model systematically investigates the influence mechanisms of non-smooth array topology and structural parameters on flow characteristics, validated through full-scale prototype testing across multiple operating conditions. The findings provide theoretical foundations for hydraulic performance optimization of wide-range ESPs and advance the engineering application of bio-inspired drag reduction technologies in intelligent oil production systems.