* 21. Which of the following statements is not true about variation of friction factor, f, in a circular pipe? a. f is inversely proportional to Reynolds number, Re, in laminar flow b. f is independent of Re at very large Re. c. f is zero for laminar flow for perfectly smooth pipe surface 6. f is proportional to the pressure loss 22. A Newtonian fluid is contained in the annulus between two concentric cylinders. The inner cylinder is rotated while the outer cylinder remains fixed, in order to shear the fluid. The viscosity of the fluid is likely to: a. increase Ⓐ remain constant c. decrease d. depend on the shear rate