Fig. 6From: Light/dark cycle enhancement and energy consumption of tubular microalgal photobioreactors with discrete double inclined ribsAveraged L/D cycle frequency of three types of PBRs with different L*. L* = 0 represents the PBR without ribs, i.e., the smooth PBR, which serves as a benchmark here; the incident light intensity is a 375 μmol m−2 s−1, b 800 μmol m−2 s−1 and c 1200 μmol m−2 s−1Back to article page