Optimization study on the layout of multi-valve assembly sections based on hydraulic characteristics

• Cavitation is prone to occur under conditions of high pressure differential, large flow rate, and valve structures that impede smooth water passage. • A sudden expansion structure serves as a simple and effective method for suppressing cavitation. • Appropriate three-dimensional scaling of the sudden expansion body downstream of the combined valve assembly can reduce the length of the jet core potential region and mitigate wall pressure. Moreover, a properly sized sudden expansion body offers broader applicability. • An optimized spatial arrangement of the combined valves significantly enhances the cavitation resistance of the valve section and also facilitates construction. In confined spaces, the valve section layout featuring "three parallel valves + rectangular sudden expansion" can achieve precise flow supply and effectively improve anti-cavitation performance. However, this configuration occupies excessive lateral space structural discontinuities like rectangular corners are prone to stress concentration. An undersized sudden expansion length leads to strong jet impact from multiple valves on the sidewalls, compromising pipeline safety. This study establishes a 3D numerical model focusing on combined valves and their downstream sudden expansions. It investigates the influence of expansion length, edge distance, valve spacing, and valve arrangement patterns on the pressure and hydraulic characteristics of the valve section. Optimal parameter ranges and an improved valve configuration were identified, enhancing anti-cavitation performance, pipeline safety, universality, and construction convenience. Sensitivity analysis revealed that a triangular 3D valve arrangement significantly increases the time-averaged pressure on the expansion sidewalls, while the effects of expansion length, valve spacing, and edge distance are relatively minor.