Author(s): Laura Coombs; Gustavo de Almeida; Sergio Maldonado
Linked Author(s):
Keywords: Fluid-cell interactions; Microalgae
Abstract: Microalgae are main primary producers and key to maintain healthy ecosystems. Interest in these organisms continues to rise as they represent a promising candidate for use as a carbon capture and can synthesize high value-added products such as beta-carotene. Algae cultivation typically takes place in shallow flows such as those found in algae raceway ponds. A crucial element in the success of the growth of microalgae is the nature of the surrounding flow and its effect on the submerged cells. The interaction between microalgal cells and complex fluid flows and the resulting cellular orientation is therefore relevant in many industrial and environmental settings. Cellular alignment has been linked to concentration depletion, effects on light propagation through the suspended medium, ability for cells to respond to other stimuli and can be used to calculate the forces and torques experienced by the cells. Prior work in this field does show preferred orientation of cells but is limited to simple shear flows with a singular velocity gradient. Real flows experienced by algae are significantly more complex from a hydrodynamic perspective, as is the case with open channel flows. We therefore propose to build on previous works and include additional complexity by considering multiple gradients in the flow. This is a novel approach that provides a more accurate representation of naturally occurring flows. The expected orientation of microalgal cells under a given fluid flow can be predicted, to a good approximation, by using the theory of Jeffery orbits (Jeffery, 1922). This too has been limited to singular gradient flows. In this work we apply said theory to a multi-gradient 3D flow for a given cell aspect ratio, and check whether the theory agrees with experimental results.
Year: 2025