Functional differential equations for the determination of the viscosity function in a rheometer (Q919167)

The helical screw rheometer is an instrument developed by \textit{A. M. Kraynik} and others [42nd Annual Technical Conference, SPE, New Orleans, 405-408 (1984); Advances in Rheology, Vol. 4, 77-84 (1984)] for obtaining the viscosity function of simple non-Newtonian fluids. The purpose of the paper under review is to determine the viscosity function which is the purpose of the rheometer. The authors transform the above problem into the existence and uniqueness of the solution to a system of functional differential equations to solve the problem.