Research on hydraulic characteristics and parameter optimization of biomimetic nozzles

The biomimetic nozzle was designed based on the drag reduction properties of the earthworm’s non-smooth surface structure. The impact force of a submerged water jet and the velocity test using particle image velocimetry (PIV) were performed on nine different types of biomimetic nozzles. The impact force measurement test revealed that the highest water jet impact force was 1.67 kg. The impact force is influenced by four parameters: diameter (d) > groove width (P1) > groove depth (P2) > number (N). The PIV velocity monitoring test showed that the axial velocity at the spray center is relatively high, decreasing progressively toward the two edges. Submerged vertical jet's velocity component is primarily axial (U), with minimal radial component (V). The velocity component of the submerged vertical jet is mainly U, and V is very small. As the injection distance increased, U was distributed across the entire cross-section in a shape similar to a normal density function. In order to comprehend the drag reduction process of biomimetic nozzles, computational fluid dynamics (CFD) simulations were utilized to analyze the internal flow field properties of the nozzles. The velocity, turbulent kinetic energy, and shear stress distribution properties at the top and bottom of the grooves were compared and evaluated for nine biomimetic nozzles. No. 1, No. 4, and No. 7 have relatively strong overall drag reduction performance, which corresponds to greater levels of water jet impact force. Optimization of design variables using the response surface methodology (RSM) and multi-objective genetic algorithm (MOGA) yielded the optimal combination: groove width P1 = 2.7 mm, groove depth P2 = 3.2 mm, and groove spacing P3 = 10.6 mm. Experimental verification showed that the optimized biomimetic nozzle has greatly enhanced hydraulic performance. This method introduces a new approach to optimizing nozzle parameters and provides theoretical support for engineering design applications.