Enzymatic reactions - Laminar flow + Transport of diluted species

Hi !

I would like to stimulate a simple reaction A=>P (in presence of E) by considering A as substrate, E as enzyme and P as product. This reaction will takes place inside a rectangular glass capillary filled with water . Width = 0.08mm and Height = 2mm are the dimensions of the capillary.

A and E are two species which give rise to one species P. species E is involved in the reaction but not consumed whereas A is consumed in the reaction. For this, I have coupled two physics "Laminar Flow" and "Transport of diluted species". In Laminar flow, I selected the inlet and outlet boundary conditions. Now, I coupled the velocity from laminar flow to transport of diluted species.

I am facing the issue that, I could select only one species column in transport of diluted species setting.

Please guide me, to select multiple species in transport of diluted species setting. My overall goal is to see the concentration of product produced from given substrate concentration and also how the substrate concentration varies with time according to the product produced.

Thanks