The Experts below are selected from a list of 16884 Experts worldwide ranked by ideXlab platform
P. Donald Ariel - One of the best experts on this subject based on the ideXlab platform.
-
Stagnation point flow of a Viscoelastic Fluid towards a moving plate
International Journal of Engineering Science, 1995Co-Authors: P. Donald ArielAbstract:Abstract The laminar, steady stagnation point flow of a Viscoelastic Fluid towards a moving plate is investigated. Both the cases of two-dimensional and axi-symmetric flow are considered. The motion of the plate gives rise to a new boundary value problem (BVP) in which the order of differential equation exceeds the number of boundary conditions. For the case of two-dimensional flow a simple solution is shown to exist, but for the axi-symmetric flow the BVP has been solved numerically, first, without making any assumption on the size of Viscoelastic Fluid parameter, and then using a perturbation solution. It is shown that the perturbation solution gives acceptable results only for very small values (O(10 −2 )) of the Viscoelastic Fluid parameter.
-
The flow of a Viscoelastic Fluid past a porous plate
Acta Mechanica, 1994Co-Authors: P. Donald ArielAbstract:The flow of a second order Viscoelastic Fluid past a porous plate is considered. It is characterized by a boundary value problem in which the order of the differential equation exceeds the number of available boundary conditions. The boundary value problem is solved by making a plausible assumption, namely that the variation of the normal derivative of the velocity at the plate withk is sufficiently smooth, wherek is the Viscoelastic Fluid parameter. Under this assumption it is shown that dual solutions exist for values ofk less than a critical value. Beyond this value, no solution exists.
A S Gupta - One of the best experts on this subject based on the ideXlab platform.
-
stagnation point flow of a Viscoelastic Fluid towards a stretching surface
International Journal of Non-linear Mechanics, 2004Co-Authors: Ray T Mahapatra, A S GuptaAbstract:Abstract An analysis is made of the steady two-dimensional stagnation-point flow of an incompressible Viscoelastic Fluid over a flat deformable surface when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point. It is shown that for a Viscoelastic Fluid of short memory (obeying Walters’ B′ model), a boundary layer is formed when the stretching velocity of the surface is less than the inviscid free-stream velocity and velocity at a point increases with increase in the elasticity of the Fluid. On the other hand, an inverted boundary layer is formed when the surface stretching velocity exceeds the velocity of the free stream and the velocity decreases with increase in the elasticity of the Fluid. A novel result of the analysis is that the flow near the stretching surface is that corresponding to an inviscid stagnation-point flow when the surface stretching velocity is equal to the velocity of the free stream. Temperature distribution in the boundary layer is found when the surface is held at constant temperature and surface heat flux is determined. It is found that temperature at a point decreases with increase in the elasticity of the Fluid.
F.t. Pinho - One of the best experts on this subject based on the ideXlab platform.
-
Numerical Methods for Viscoelastic Fluid Flows
Annual Review of Fluid Mechanics, 2020Co-Authors: M.a. Alves, P.j. Oliveira, F.t. PinhoAbstract:Complex Fluids exist in nature and are continually engineered for specific applications involving the addition of macromolecules to a solvent, among other means. This imparts Viscoelasticity to the Fluid, a property responsible for various flow instabilities and major modifications to the Fluid dynamics. Recent developments in the numerical methods for the simulation of Viscoelastic Fluid flows, described by continuum-level differential constitutive equations, are surveyed, with a particular emphasis on the finite-volume method. This method is briefly described, and the main benchmark flows currently used in computational rheology to assess the performance of numerical methods are presented. Outstanding issues in numerical methods and novel and challenging applications of Viscoelastic Fluids, some of which require further developments in numerical methods, are discussed. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 53 is January 6, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
-
A numerical and theoretical study on Viscoelastic Fluid slip flows
Physics of Fluids, 2017Co-Authors: Luís Jorge Lima Ferrás, Alexandre M. Afonso, João M. Nóbrega, F.t. PinhoAbstract:This work describes a theoretical and numerical investigation of Viscoelastic Fluid flows, considering slip boundary conditions. The Viscoelastic Fluid is described by the simplified Phan-Thien-Tanner model, and the governing equations with slip boundary conditions are solved by a finite volume method using (1) a recently proposed methodology to control the growth of the slip velocity along the iterative process (named the SIMPLE-slip method) where some simplifications are assumed at the wall, and also (2) a slip formulation where the complete stress tensor at the wall is taken into account. Analytical and semi-analytical solutions are also provided for the fully developed flow between parallel plates of Viscoelastic Fluids, assuming Thomson and Troian and Lau and Schowalter non-linear wall slip models. For verification purposes, the numerical results were compared with the analytical solution for fully developed slip-flow in a planar channel using two non-linear slip models. Simulations were carried out ...
Ray T Mahapatra - One of the best experts on this subject based on the ideXlab platform.
-
stagnation point flow of a Viscoelastic Fluid towards a stretching surface
International Journal of Non-linear Mechanics, 2004Co-Authors: Ray T Mahapatra, A S GuptaAbstract:Abstract An analysis is made of the steady two-dimensional stagnation-point flow of an incompressible Viscoelastic Fluid over a flat deformable surface when the surface is stretched in its own plane with a velocity proportional to the distance from the stagnation-point. It is shown that for a Viscoelastic Fluid of short memory (obeying Walters’ B′ model), a boundary layer is formed when the stretching velocity of the surface is less than the inviscid free-stream velocity and velocity at a point increases with increase in the elasticity of the Fluid. On the other hand, an inverted boundary layer is formed when the surface stretching velocity exceeds the velocity of the free stream and the velocity decreases with increase in the elasticity of the Fluid. A novel result of the analysis is that the flow near the stretching surface is that corresponding to an inviscid stagnation-point flow when the surface stretching velocity is equal to the velocity of the free stream. Temperature distribution in the boundary layer is found when the surface is held at constant temperature and surface heat flux is determined. It is found that temperature at a point decreases with increase in the elasticity of the Fluid.
Eric S. G. Shaqfeh - One of the best experts on this subject based on the ideXlab platform.
-
Swimming with swirl in a Viscoelastic Fluid
Journal of Fluid Mechanics, 2020Co-Authors: Jeremy P. Binagia, Ardella Phoa, Kostas D. Housiadas, Eric S. G. ShaqfehAbstract:Microorganisms are commonly found swimming in complex biological Fluids such as mucus and these Fluids respond elastically to deformation. These Viscoelastic Fluids have been previously shown to affect the swimming kinematics of these microorganisms in non-trivial ways depending on the rheology of the Fluid, the particular swimming gait and the structural properties of the immersed body. In this report we put forth a previously unmentioned mechanism by which swimming organisms can experience a speed increase in a Viscoelastic Fluid. Using numerical simulations and asymptotic theory we find that significant swirling flow around a microscopic swimmer couples with the elasticity of the Fluid to generate a marked increase in the swimming speed. We show that the speed enhancement is related to the introduction of mixed flow behind the swimmer and the presence of hoop stresses along its body. Furthermore, this effect persists when varying the Fluid rheology and when considering different swimming gaits. This, combined with the generality of the phenomenon (i.e. the coupling of vortical flow with Fluid elasticity near a microscopic swimmer), leads us to believe that this method of speed enhancement could be present for a wide range of microorganisms moving through complex Fluids.
