Adanta, Dendy, Sari, Dewi Puspita, Syofii, Imam, Sahim, Kaprawi, Martides, Erie, Radiansah, Yadi, Subagio, Dalmasius Ganjar, Utomo, Yusuf Suryo, Rosyid, Oo Abdul, and Fudholi, Ahmad
[Display omitted] In the 19th and early 20th century, the utilization and development of the undershot waterwheel (USWW) was massif. USWW represents a global warming and crisis electricity solution issue for the world. However, the best condition and design of USWW are still incomplete; previous research is based on assumptions. Hence, this work aims to theoretically estimate the power loss (head loss, leakage loss, and friction loss) occurring in USWW to predict the relation between the blade number and optimum operation. The investigation employs analytical and CFD methods, then validated with experimental data. Then, based on root mean square error (RMSE) analysis, the average RMSE of analytical results to experimental data was 9.02%, and of CFD data was 9.07%. Then, depict the blade number and optimum operation relation to USWW performance expressing using multiple quadratic polynomial regression. The empirical law identifies the 16-blades, and the working operation of 0.5 is USWW maximum performance in ultra-low-head. [ABSTRACT FROM AUTHOR]