Fig. 3. Variation of the Reynolds number Re_f along the dimensionless length of a flicking flagellum for downward (=5.24 rad s^–1) and upward (=3.14 rad s^–1) flicks; flagellum dimensions are given in the text. The decreases in flagellum diameter and of the normal component of velocity with increasing distance toward the flagellum tip account for the reduction in Re_f with increasing z/L_f.