Viscoelastic Fluid hammer is a type of Fluid hammer in which a Viscoelastic non-Newtonian Fluid flows in a pipeline. In this study, the Fluid-structure interaction in this phenomenon is investigated. The governing equations are Viscoelastic Fluid and structure equations which are coupled together. Viscoelastic Fluid equations consist of continuity and momentum which govern the transitional flow in the pipes. Oldroyd-B model is used as the constitutive equation. This model is suitable for dilute Viscoelastic solutions and Boger liquids. Structural equations include pipe axial velocity and stress equations. A two-step variant of the Lax-Friedrichs method is used to simulate Fluid-structure interaction in a reservoir-pipe-valve system. A Viscoelastic Fluid polymer is selected and the behavior of the polymer pressure head and shear stresses during Fluid hammer is investigated. Three types of couplings were examined. Junction, Poisson, and the combination of two aforementioned couplings called junction and Poisson coupling. The effects of these couplings for the Fluid are modeled in three states. ideally, Newtonian and Viscoelastic. The Fluid viscosity in Newtonian and Viscoelastic states is considered the same. The results of the study show that the imposed shear stresses with Viscoelastic Fluid are significantly lower than those in the Newtonian state. Comparing coupling effects during Fluid hammer is found that the lowest shear stresses are assigned to Poisson coupling.

This communication in uences on magnetohydrodynamic ow of Viscoelastic uid with magnetic  eld induced by oscillating plate. General solutions have been found out for velocity and shear stress pro les using mathematical transformations (integral transforms). The governing partial di erential equations have been solved analytically under boundary conditions u(0; t) = A0H(t)sin( t) and u(0; t) = A0H(t)cos( t) with t  0. For the sake of simplicity of boundary conditions are veri ed on the analytical general solutions and similar solutions have been particularized under three limited cases namely (i) Maxwell uid without magnetic  eld if 6= 0; M = 0 (ii) Newtonian uid with magnetic  eld if = 0; M 6= 0 and (iii) Newtonian uid with out magnetic  eld if = 0; M = 0. Finally various physical parameters with variations of uid behaviors are analyzed and depicted graphical illustrations.

An analytical solution is presented for the steady state and purely tangential flow of a nonlinear Viscoelastic Fluid obeying the constitutive FENE-P model in a concentric annulus with inner cylinder rotation. The effect of Fluid elasticity (Weissenberg number), the extensibility parameter of the model (L2 ) and aspect ratio on the velocity profile and production of friction factor and Reynolds number (¦¢Re) are investigated. The results show the strong effect of Viscoelastic parameters on the velocity profile. The results also show that ¦¢Re decreases with increasing Fluid elasticity and radius ratio.

The present work tries to obtain a simple means of simultaneous measurement of steady shear viscosity and normal stress difference in polymer melts and high concentrated solutions. The task is performed by using a rotating rod viscometer. In the experiments the steady shear viscosity is obtained by the measurement of the torque and the normal stress difference obtained by measuring the free surface height developed due to the rod climbing (Weissenberg Effect).A one dimensional unsteady modeling of the nonlinear Viscoelastic flow using Leonov model will enable us to obtain the time dependent torque and the free surface height at various shear rates for a given Fluid. Hence, the device is calibrated for a known Fluid, and by using the calibration curves and reading the torque and free surface height, the steady shear viscosity and the normal stress di1terence could be obtained for any Fluid by using the obtained numerical simulation data.

Feedback control is applied to the problem of a Viscoelastic Jeffreys Fluid layer heated from below to investigate conditions for delay of the onset of convection. Interesting results for fixed Prandtl number 1 and 10 were found showing that for some conditions proportional control may not work as expected. Also, some limits of the feedback control in terms of the parameters of the system through an analytical approach by mean of the Galerkin method are discussed. In order to complete the study a numerical analysis was also performed to map the space of physical parameters. The results of this work are discussed and compared with results of previous authors while attention to small control adjustments is paid.

In this paper, applying the general form of the Viscoelastic model, vibration characteristics of Viscoelastic Fluid conveying pipes are investigated. By considering various Viscoelastic constitutive equations, the equation governing the motion of the Fluid conveying pipes is obtained, and by introducing a new analytical method, the exact mode shapes of the system are derived. Then, the effect of various system parameters on the complex eigenvalues and the instability of kind divergence and flutter are studied. The results show that for a pipe with Viscoelastic behavior, the natural frequencies decrease and at the higher modes, the divergence critical Fluid velocity increases dramatically. As a new result, it is observed the Viscoelastic Fluid conveying pipes with certain values of Viscoelastic parameters, can experience the flutter instability before the divergence one. In addition, because the Viscoelastic behavior does not affect all the vibration mode shapes in the same manner, therefore, the coupled-mode flutter does not take place.

In this article, the laminar flow of an incompressible and Viscoelastic Fluid inside a channel with porous walls has been investigated using optimal asymptotic homotopy method (OHAM). The flow inside the channel is considered steady and the Darcy model is used to simulate the effects of drag on the flow caused by the porous medium. The governing equations of the problem are converted into non-linear ordinary differential equations and solved. To prove the correctness of the solution, some of the results have been compared with the obtained numerical results. The effects of Darcy number, Deborah number and Reynolds number on the velocity distribution are analyzed. Based on the comparison, the ability and high accuracy of this method to solve the problem has been determined. Finally, it can be concluded that this method can be used as a reliable method to solve the internal flow of Fluid inside a channel with a porous wall.

Nano-bio particle separation has been widely implemented in diagnosis and treatment in the medical area. Nano-bio particles such as virus, DNA, protein and exosome contain significant information that can help in the diagnosis and treatment of diseases like cancer. In this article, Viscoelastic Fluid in the OldRoyd-b model is simulated in a steady state in COMSOL 6.1 multiphysics In the first stage and to calculate the net of inertial lift force on the particles, a direct numerical approach has been implemented through coupling a FEM solver and a code developed in MATLAB. Considering quadrilateral geometry as an applicable microchannel, the aspect ratio effect on Nano-bio particles focusing in the Viscoelastic Fluid is investigated in a range of particle size of 100 to 1000 nanometer in Reynolds number 8 and polymer concentration 0.1%. Results show single line focusing has not been seen greatly in the channel with an aspect ratio greater than 1, but complete single line focusing has happened in channel with an aspect ratio of 1 in the dilute Viscoelastic flow for particles greater than 500nm up to 1000nm.

Nowadays, simulation of Viscoelastic flows at high Weissenberg numbers is one of the most obstacles and important issues for rheologists to observe the rheological properties at sufficiently high weissenberg number. It is well known that the conformation tensor should, in principle, remain symmetric positive definite (SPD) as it evolves in time. In fact, this property is crucial for the well-posedness of its evolution equation. In practice, this property is violated in many numerical simulations. Most likely, this is caused by the accumulation of spatial discretization errors that arise from numerical integration of the governing equations. In this research, we apply a mathematical transformation, the so-called hyperbolic tangent, on the conformation tensor to bound the eigenvalues and prevent the generation of negative spurious eigenvalues during simulations. The flow of FENE-P Fluid through a 2D channel is selected as the test case. Discrete solutions are obtained by spectral/hp element methods which based on the high orders polynomials and have high accuracy for physical instability problems. This enhanced formulation, hyperbolic tangent, prevails the previous numerical failure by bounding the magnitude of eigenvalues in a manner that positive definite is always satisfied. Under this new transformation, the maximum accessible Weissenberg number increases 100% comparing the classical constitutive equation (FENE-P classic).