CFD-based investigation of blade thickness ratio effects on pico-hydro crossflow turbine performance

Indonesia’s vast hydropower potential remains significantly untapped, despite the relevance of low-head water resources for decentralised rural electrification. This study investigates the effect of the blade thickness ratio (L/H) of a centre-convex upper blade profile on the hydraulic performance of a pico-hydro crossflow turbine. The novelty of this work lies in isolating L/H as a manufacturable blade-profile variable and linking its influence to velocity-triangle design, transient CFD results, benchmark comparison, and flow-field mechanisms. The numerical model was assessed through mesh independence, time-step independence, analytical benchmark comparison, and comparison with relevant literature. The reported efficiency is therefore interpreted as runner-domain hydraulic efficiency rather than complete electro-mechanical system efficiency. The optimum L/H ratio of 0.5 achieved 81.80% hydraulic efficiency and 210.07 W mechanical power at 600 rpm under a 3 m head. This performance is associated with a favourable pressure difference, smoother streamlines, and delayed separation, whereas the thickest blade (L/H of 1.5) produced stronger blockage, recirculation, and efficiency reduction to 56.31%. The results provide design guidance for locally manufacturable pico-hydro crossflow turbines and establish a basis for future prototype validation and field installation in remote Indonesian communities.