Stir your suspension with a rod.. if you observe increase in viscosity, then its a dilatant... if you see no change or decrease in viscosity then its a shear thinning fluid.

Rheology and mathematics always go hand-in-hand.. since rheological property of a fluid is not a intrinsic variable, its a state variable.. 

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You are right about the stirring test, however during the high pressure filtration in a narrow column (used for chromatographic purposes), one starts with a dilute suspension. As the bed forms under constant pressure the suspension becomes more and more concentrated and this is where those non-Newtonian effects come into play. Are you familiar with any studies which show the bed structure  as a function of rheological property?

Dear colleague

It seems that vane Rheometer help you to find if you measure viscosity two times.at first make it steady or 20 minute then measure and again measure.

and you may Define its origin as an example the electric charge of  particles and their effects.

for simulations you may use MD,maybe eventuate to a good answer

regards

Mahdi,we do not have a rheometer, thats why I was interested to know if chemical engineers do qualitative tests for non-Newtonian suspensions. The stirring rod test is very observational; are there other observational tests which can reveal the nature of the suspension e.g. optical microscopy?

Can you measure the particle size distribution?  If so, this can be used to calculate the random close packing fraction.  This value can be used to determine 'zero shear plateau' viscosity as a function of particle volume fraction.  Please see the linked article, Analytically predicting the viscosity of hard sphere suspensions from the particle size distribution. Heather M. Shewan , Jason R. Stokes. 

http://www.sciencedirect.com/science/article/pii/S0377025714001463

connect with someone at your university having a rheometer. If you would have a LUMiSizer or LUMifuge you could measure settling velocity as function of acceleration revealing Newtonian, shear thickening or thinning behaviour or a yield point.

There countless papers on filtration of solids. Many address measuring the behaviour of the materials. If you want a list of some reading material I could give you some starting points. I assume you are looking for dewatering parameters, hindered settling function and compressive yield stress?

@ Adam, One of the critical steps in chromatography is to pack very small spheres of silica (or any other material) into narrow columns e.g. 4.6 mm diameter under a very high pressure, say 5000 psi up to 30,000 psi depending on the particle size. The quality of the packed bed is determined by the rheological properties of the slurry. The packed bed in turn affects how well one can separate the components of a mixture. In the (non-engineering) chemist's literature, this process is termed as the art of packing columns. People do many experiments to find the conditions of the best bed. Are you aware of some classic works on ultra high pressure filtration which monitor the quality (porosity, structure etc.) of the filtered bed?

Thank you Dr. Sobisch. What is the working principle of your centrifuges which determine the nature of the slurry?

During centrifugation with multiple samples at preset time intervals light transmission is determined over the whole sample length simultaneously. Therefore you can observe separation behaviour (polydisperse or zone separation) and determine separation velocity, degree and packing density. Running experiments at different accelerations give you results as function of acceleration. This way you can distinct Newtonian, shear thickening or thinning behaviour.

For the filling of silica into the columns theoretically best results would be expected when you fill colloidal stable silica dispersions of medium particle concentration slowly into the columns. Stabilization might be achieved using polyphosphate, metasilicate, polycarboxylates, anionic or nonionic surfactants. Higher particle concentration should suppress particle sorting by size.

Dr. Sobisch, I think this is exactly what I was asking. Could you please share how does your Lumifuge determine the nature of the bed, I mean what data do you get which determines whether the slurry was Newtonian or not? Does it determine the bed height at various accelerations? Is a there a qualitative way to do that?

Can you recommend a classical paper on the theory you just mentioned based on packing colloidally stable suspensions, which give the highest quality beds? 

Thank you.

A lumifuge I have seen was for lower pressures than what you are talking about. This one worked on light transmittance through the slurry. you set an intensity as the so called slurry height (clear water on top) and do calcs similar to a transient batch settling test (measuring cylinder batch settling).

Farooq - most of my experience is based around lower pressures (

Thank you Adam,

related to the basics is that if you have a colloidal stable dispersion, i.e. stable against agglomeration packing density only slightly depends on pressure - for low pressures and for high pressures as well. See e.g.

J.A. Lewis, Colloidal Processing of Ceramics, J. Am. Ceram. Soc. 83 (2000) 2341-59.

An example for LUMiFuge application in this field

T. Sobisch, D. Lerche, T. Detloff, M. Beiser, A. Erk, Tracing the centrifugal separation of fine-particle slurries by analytical centrifugation, Effect of centrifugal acceleration, particle interaction and concentration, Filtration 6 (2006) 313-321.

Thank you Dr. Sobisch. I will read the references. From the column packing experience under a constant pressure, it turns out that a colloidally stable slurry, with too much of electrostatic repulsion, shows severe shear thickening effect. Under pressure, the packed column is a hard solid but when the pressure is removed it becomes a liquid again- just like a corn starch suspension. Even if such a shear thickening suspension is packed tightly, the injected band of an analyte comes out as a non-Gaussian distribution. It usually has a front. How would you explain this behaviour?

Is this true in general that all shear thickening suspensions are the ones in such particles have electrostatic repulsion?

I ones read a very nice explanation about shear thinning and shear thickening related to ceramic dispersions. While the first is about interparticle forces the latter is due to high shear forces and high concentration. Therefore I suggested to pack the columns starting from not to high particle concentration. You have to do this slowly. Otherwise there will be allot of defects. You should be aware, however, that high packing density also means high resistance, high cake resistance in filtration. Therefore, maybe weak flocculation might be more suitable for you. You could play with electrolyte concentration to get optimal packing. Lowering packing density by flocculation means, however, higher compressibility.

Publications by Peter Scales (Univ. Melbourne) on "compressive rheology" may be useful to consider in addition to the discussion above.