Effect of hydrodynamical conditions on a microalgae culture growth was investigated in a photobioreactor with annular light chambers, with the focus on the relation between the cell displacement and the amount of light received by microorganisms, by comparing two different flow conditions in light chambers: an axial flow generating a poor radial mixing and a 3‐D swirling motion. To determine microorganism trajectories, a Lagrangian approach was retained, allowing light received to be considered from a single microalga point of view. The light distribution was calculated using Beer–Lambert law, and a biological modeling of the culture growth was proposed, with consideration of light/dark cycle effects induced by cell displacement in the depth of the culture. Finally, batch cultures of Porphyridium purpureum were simulated for both hydrodynamical conditions in light chambers. The advantage of applying a three‐dimensional motion to generate cell renewal in front of the light source, allowing microorganisms to use light more efficiently, is clearly shown.

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