“…Several examples of Francis turbine runner optimization exist (Enomoto, Kurosawa, & Kawajiri, 2012;Nakamura & Kurosawa, 2009;Pilev et al, 2012), some even optimizing the runner and draft tube simultaneously (Lyutov, Chirkov, Skorospelov, Turuk, & Cherny, 2015). Most of these attempts deal with medium-to-high specific speed Francis turbines, but other turbine types have also been optimized using similar techniques (Ezhilsabareesh, Rhee, & Samad, 2018;Semenova et al, 2014). The peak efficiency of hydro turbines has not increased much in the last decades, as noted in Electric Power Research Institute (1999) and Lyutov et al (2015).…”