The form resistance of sinking algal chains

The relationship between sinking velocity and chain length was investigated in a species of Anabaena and with physical models constructed from glass beads.The sinking velocities of glass bead chains from one to 30 beads long were measured in tanks of glycerol, ensuring low Reynolds numbers, with the chains orientated in both horizontal and vertical directions.The coefficient of form resistance (~b) for each length and attitude was calculated as a correction factor in the Stokes equation.Average sinking velocities of the Anabaena chains were found to fall within the range of velocities predicted from the Stokes equation with the appropriate values of ~b determined from measurements wi~h the physical models.