37 The following readings were taken with a rotational viscometer. N ON 3 4.5 6 5.5 100 9.0 200 14.5 300 19.0 600 32.5 a. Using the power-law model, compute the fric- tional pressure gradient resulting from a 50-gal/min flow rate in a 2.9-in.-ID drillpipe. Assume the flow pattern is laminar. Answer: 0.00586 psi/ft. b. Compute the shear rate at the wall of the drillpipe. What two rotational readings would you expect to give the best n and K factors for the pressure gradient computation. Answer: 86 seconds-1 c. Make a plot of flow velocity vs. pipe radius and a plot of shear stress vs. pipe radius.