USE MATLAB TO SOLVE

Using the data shown in Figure 4.5, find the best values of s and y in the Casson equation that fit these data. Recall that the shear stress can be found from the data shown in Figure 4.5 from the following relationship, t m = apparent g. Also, from the Casson equation, note that a plot of 1/2 versus g1 2/ should be linear with a slope equal to s and an intercept of ty 1 2/ . Express the units of s as (dynes s cm2)1/2 and y in (dynes cm2).

4.7.2 Using the Casson equation For a Casson fluid like blood, we can rearrange Equation 4.25 and solve for the shear rate, ie., (u in terms of the shear stress, Tri 1/2_1/2 .) (4.26) The shear stress-shear rate relationship for blood can be described by the following empirical equa- tion known as the Casson equation: (4.25) In this equation, T, is the yield stress and s is a constant, both of which can be determined from vis cometer data. The yield stress represents the fact that a minimum force must be applied to stagnant Trz Po Figure 4.5 Forces acting on a cylindrical fluid element within a capillary viscometer. 166 4.7.2 Using the Casson equation For a Casson fluid like blood, we can rearrange Equation 4.25 and solve for the shear rate, ie., (u in terms of the shear stress, Tri 1/2_1/2 .) (4.26) The shear stress-shear rate relationship for blood can be described by the following empirical equa- tion known as the Casson equation: (4.25) In this equation, T, is the yield stress and s is a constant, both of which can be determined from vis cometer data. The yield stress represents the fact that a minimum force must be applied to stagnant Trz Po Figure 4.5 Forces acting on a cylindrical fluid element within a capillary viscometer. 166