Peristaltic transport of viscoelastic bio-fluids with fractional derivative models

Peristaltic flow of viscoelastic fluid through a uniform channel is considered under the assumptions of long wavelength and low Reynolds number. The fractional Oldroyd-B constitutive viscoelastic law is employed. Based on models for peristaltic viscoelastic flows given in a series of papers by Tripathi et al. (e.g. Appl Math Comput. 215 (2010) 3645–3654; Math Biosci. 233 (2011) 90–97) we present a detailed analytical and numerical study of the evolution in time of the pressure gradient across one wavelength. An analytical expression for the pressure gradient is obtained in terms of Mittag-Leffler functions and its behavior is analyzed. For numerical computation the fractional Adams method is used. The influence of the different material parameters is discussed, as well as constraints on the parameters under which the model is physically meaningful

A Compact Alternating Direction Implicit Scheme for Two-Dimensional Fractional Oldroyd-B Fluids

[Vasileva Daniela; Василева Даниела]; [Bazhlekov Ivan; Бажлеков Иван]; [Bazhlekova Emilia; Бажлекова Емилия]The two-dimensional Rayleigh-Stokes problem for a generalized Oldroyd-B fluid is considered in the present work. The fractional time derivatives are discretized using L1 and L2 approximations. A fourth order compact approximation is implemented for the space derivatives and two variants of an alternating direction implicit finite difference scheme are numerically investigated. 2010 Mathematics Subject Classification: 26A33, 35R11, 65M06, 65M22, 74D05

Nonsingular boundary integral method for deformable drops in viscous flows

A three-dimensional boundary integral method for deformable drops in viscous flows at low Reynolds numbers is presented. The method is based on a new nonsingular contour-integral representation of the single and double layers of the free-space Green's function. The contour integration overcomes the main difficulty with boundary-integral calculations: the singularities of the kernels. It also improves the accuracy of the calculations as well as the numerical stability. A new element of the presented method is also a higher-order interface approximation, which improves the accuracy of the interface-to-interface distance calculations and in this way makes simulations of polydispersed foam dynamics possible. Moreover, a multiple time-step integration scheme, which improves the numerical stability and thus the performance of the method, is introduced. To demonstrate the advantages of the method presented here, a number of challenging flow problems is considered: drop deformation and breakup at high viscosity ratios for zero and finite surface tension; drop-to-drop interaction in close approach, including film formation and its drainage; and formation of a foam drop and its deformation in simple shear flow, including all structural and dynamic elements of polydispersed foams

Spreading of a wetting film under the action of van der Waals forces

The profiles of a spreading wetting film are computed using a variable grid implicit scheme. The form of Tanner's law is deduced from the scaling, and the dependence of its coefficient on ratio of the van der Waals to the capillary length and on the inclination angle is determined