Question: Need help with this question. Please send full solution. 1) The following data were taken in a Couette viscometer with an inner cylinder radius of
Need help with this question. Please send full solution.
1) The following data were taken in a Couette viscometer with an inner cylinder radius of 2 cm, outer cylinder radius of 2.05 cm, and an axial length of 15 cm. Note that in Couette viscometers, the outer cylinder is rotating. The goal is to determine viscosity from these data. Torque Speed (dyn cm) (rpm) 2,000 3,500 4 7,200 10 12,500 20 20,000 40 (a) To determine the viscosity, first you need to know if the fluid is Newtonian or not. If it is Newtonian, then equation 3.6.31 (page 91 of the textbook) is valid. Show that the data is not consistent with this equation? (b) Now let's model the fluid as a Power-law fluid where n =- I _my = my"-1. Since the y Y outer cylinder is rotating, the shear rate on the inner cylinder surface and the equation for the model that best represents this viscosity can be obtained. Use equation 8.3.20 (page 244) to show that the shear rate at the inner cylinder surface is given by: ' inner cylinder n 2 where B = R. (i) Now, using the relationship, inner cylinder = my inner cylinder (ii) show that, In Torque 2nLR, vs. In 2. plot where Torque = 27 LR, r has a slope of n (c) Expand the table above with the corresponding values of shear stress, shear rate, and viscosity for each experimental data shown. (d) Obtain the value of m from the plot of log eta vs. log shear rate
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