Shear Rate Determination (disc spindles) 1

hi keepuh,

I am just browsing here and found your posting, about 6 months ago. I suppose you have solved your problems.
I have a similar situation, and have given a bit of thought to it, but had no chance to discuss it with someone.

In an open cup, there is no single value for the shear rate in the liquid. There is, instead, a distribution of values of the shear rate that depends on the rheological characteristics of your liquid, the geometry of your system, and the speed of the disk spindle.

I am using an average value estimated from the total amount of energy that I have to deliver to the system, and accurate viscosity measurements done on a cone-plate or concentric cylinders rehometer. The shear rate will have its higher values in the neighborhood of the spindle, and lower values farther away from it. That is why an open cup and spindle rehometer, like most Brookfield can only provide relative measurements, rather than exact values.

If you are interested in a more detailed discussion let me know.

Best regards,

Gianfranco Mazzanti