1. INTRODUCTION
The water turbines can be classified into two major kinds: the axial-flow rotors
(AFR) and the cross-flow rotors (CFR). The simplicity of the blade shapes and the
independence of the water current direction give the advantage to the CFR for the
generation of small-scale hydropower with regard to the AFR. With the aim of
performance enhancement of CFR, numerous computational and experimental
tests were conducted recently. For example, Moghimi and Motawej (2020) carried
out a computational test of a twisted Darrieus water rotor (TDWR). They
investigated the impact of the twist angle on the operational parameters of the
TDWR. In conclusion, the lowest coefficient of power value was obtained with...
