I haven't found any papers or articles specifically addressing axial pump viscosity-related performance predictions but there are many on centrifugal pumps that might provide data applicable to axial flow pumps. Some of the more general centrifugal pump sources are:
Hole,Gunnar,1994, "Fluid Viscosity Effects on Centrifugal Pumps", Pumps and Systems Magazine, April, pp.14-19
Engin,T.& Gur,M.,2003,"Comparative Evaluations of Some Existing Correlations to Predict Head Degradation of Centrifugal Slurry Pumps", ASME J.Fluids Engineering, Vol.125, Jan. pp.149-157
Gandhi,B.K.etal,2001,"Performance Characteristics of Centrifugal Slurry Pumps", ASME J.Fluids Engineering, Vol.123, June, pp.271-280
The 1st article gives a curve fitted equation for Hydraulics Institute viscosity curves and an example of its use in viscous flow horsepower calculations.