A fine thread of dye is injected along the axis of water flowing steadily through a horizontal glass tube. The thread remains straight for the first 20cm of the tube and then begins to oscillate and mix with the surrounding water.
a. (i) State the type of flow in the first 20cm section.
b. (ii) State the type of flow in the later section where mixing occurs.
c. (iii) Give a brief reason for the change in flow pattern along the tube.