Authors: MEHMET KOPAÇ
Abstract: In this study using some existing constitutive equations, a modified Jeffreys type model with retardation time is developed which is successful with the experimental data for simple shear flow and shear free flow. Nonlinear regression analysis based on Marquardt Algorithm is used for determination of material parameters for simple shear flow. The general form of the modified model is reduced by using the simple shear flow conditions and Oldroyd derivative for cartesian coordinates. In the determination of material parameters of the modified model is used experimental data of Leider and Lilleleht(1973) for viscometric functions. When viscometric functions of the modified model is compared with viscometric functions of the existing constitutive equations which use the material parameters of Leider and Lilleleht(1973), viscometric functions of the modified model is found to be more successful.
Keywords: Viscoelastic fluids; Nonlinear regression; Numerical simulations; Constitutive equations
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