Lumley 



Peebles, The Flow of a Non-Newtonian Fluid in a Diverging Duct, experimental; 

 Department of Engineering Mechanics Report, August 1964, University of Tennes- 

 see, Knoxville, Tennessee) and they found it to be a shear -thinning, visco-inelastic 

 fluid. 



Figure 1 shows the viscosity variation with shear rate of a particular sample 

 of Milling Yellow as computed from data obtained with a capillary viscometer. 



50 



40 



30 



100 



200 



SHEAR 



300 

 RATE 



400 

 / sec"' -*■ 



500 



600 



Fig. 1 



Rheological data for milling yellow: 

 1.608% concentration 



The stability experiment performed is the well-known Taylor experiment in 

 which one studies the motion of the fluid in the gap between two concentric cylin- 

 ders rotating at different speeds. In our experiment the outer cylinder is sta- 

 tionary and only the inner one rotates. Because of the shear rate dependence of 

 the viscosity the tangential velocity profile in the gap is different from that of a 

 Newtonian fluid. Figure 2 shows a comparison between the two for identical 

 boundary conditions at the inner (R = 3.14 cm) and the outer cylinder (R = 3.49), 

 obtained by computation using the experimentally determined viscosity. 



940 



