The present paper is concerned with the steady thin film flow of the Sisko fluid on a horizontal moving plate, where the surface tension gradient is a driving mechanism. The analytic solution for the resulting nonlinear ordinary differential equation is obtained by the Adomian decomposition method (ADM). The physical quantities are derived including the pressure profile, the velocity profile, the maximum residue time, the stationary points, the volume flow rate, the average film velocity, the uniform film thickness, the shear stress, the surface tension profile, and the vorticity vector. It is found that the velocity of the Sisko fluid film decreases when the fluid behavior index and the Sisko fluid parameter increase, whereas it increases with an increase in the inverse capillary number. An increase in the inverse capillary number results in an increase in the surface tension which in turn results in an increase in the surface tension gradient on the Sisko fluid film. The locations of the stationary points are shifted towards the moving plate with the increase in the inverse capillary number, and vice versa locations for the stationary points are found with the increasing Sisko fluid parameter. Furthermore, shear thinning and shear thickening characteristics of the Sisko fluid are discussed. A comparison is made between the Sisko fluid film and the Newtonian fluid film.

This paper investigates the thin film flow of Phan-Thien Tanner (PTT) fluid on a vertically moving belt. Three different models, namely, the upper convected Maxwell model (UCM), linear version of Phan-Thien Tanner model (LPTT), and exponential version of Phan-Thien Tanner model (EPTT), are taken into consideration. Exact expressions for velocity profiles, flow rates, average velocities, film thicknesses, shear stresses, and normal stresses are obtained. Special consideration is given to the predictions of stationary points in withdrawal of these fluids from the belt. It is observed that the stationary point of the UCM model lies closer to the free surface and the stationary point of the LPTT model lies in the middle of the stationary points of UCM and EPTT models. It is also observed that the stationary points tend to move towards the belt with the increase in Stokes number, Deborah number, and elongational parameter. Graphical results are also presented for various dimensionless flow parameters.

This paper provides the exact solutions for the fully developed two layer pressure driven flows of incompressible Phan-Thien-Tanner fluids in a horizontal cylindrical pipe. Exact equations are formulated and solved for important kinematic properties, such as, velocity profiles, normal and shear stresses, total volume fluxes through a circular cross-section and average velocities. Graphical results are provided and discussed for the different flow parameters. A comparison of Upper Convected Maxwell (UCM), Linear Phan-Thien-Tanner (LPTT) and Exponential Phan-Thien-Tanner (EPTT) shows that UCM is a low viscosity fluid as compared to LPTT, and EPTT and LPTT is lighter than EPTT. 379Open Journal of Fluid Dynamics components in both geometries. Some other studies regarding PTT have been carried out in [5] [6] [7]. Letelier and Siginer [8] studied the problem of fully developed pipe flow of a class of nonlinear viscoelastic fluids which include PTT and Johnson-Segalman models as special cases. Some other works using PTT fluid have been carried out by Siddiqui et al. in [9]. All these studies are based on the flow of a single PTT fluid. This paper however, deals with a two-layer concentric flow of two immiscible PTT fluids in a single pipe. Recently, the interest in stratified laminar flow of two or more immiscible fluids where the superscript k denotes the two fluids, the number 1 k = represents the fluid in the core, while the fluid properties for the outer fluid along the wall are denoted by the superscript 2 k = . ( ) k V , ( ) k ρ , ( ) k T are the velocity, density A. M. Siddiqui et al.

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