ON THE RELATIONSHIP BETWEEN THE ATTACHED ALGAE GROWTH ON THE SURFACE OF A CIRCULAR CYLINDER AND THE WATER FLOW CHARACTERISTICS AROND IT

Abstract

Shallow urban rivers, receiving nutrient-enriched effluent, have thick growths of algae on their beds. Such algae deteriorate the water quality of those rivers by their respiration and detachment from the beds. Therefore it is significant to study the characteristics of the behavior of the attached algae for understanding the water pollution mechanism of the rivers.
In this study, to investigate the effects of the flow on the growth of the attached algae, the algal growth on the surface of a circular cylinder is studied. The cylinder is stood on the bed of an experimental flume perpendicular to the uniform flow and is thought to produce different hydraulic conditions around it.
In the first place the variations of the shear stress and the nutrient flux on the surface of the cylinder are theoretically considered, respectively. Then the way is shown to control those conditions by choosing appropriate values of the velocity of the uniform flow and the cylinder diameter, and the availability of using the cylinder is described.
Next, the experiments are performed following the method described above and it is examined how the shear stress and the nutrient flux at the substratum affect the growth of the attached algae.