Linear perturbation versus non-linear transient analysis in hydrodynamic lubrication
I have come across a case where modifying lubricant rheology during dynamic analysis is showing improvement in stability, when using the Linear Perturbation Approach. The dynamic stiffness and damping characteristics shows a significant increase. However, when the same problem when analyzed using the non-linear transient analysis shows no difference in stability from the classical Newtonian model. The threshold speeds are not different from that of the Newtonian case.
What could be the reasons for difference in results?
Lubricants are inherently non-Newtonian fluids, fall in the category of pseudoplastic fluids. So, classical Newtonian laws are not valid.
Newtonian model and non-Newtonian model are totally different models. If your fluid is non-Newtonian, you should use non-Newtonian, whether or not linear or non-linear.
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