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.

In this paper, the occurrence of water hammer phenomenon is examined in a situation that instead of water, an upper-convected-Maxwell fluid flows in a pipe system. This phenomenon is called an upper-convected-Maxwell fluid hammer. This expression relates to transients of Maxwell fluid caused by the sudden alteration in the conditions of flow. Upper-convected-Maxwell fluids are a kind of non-Newtonian Viscoelastic fluids. The system studied is a valve-horizontal pipe and reservoir. The equations representing the conservation of mass and momentum govern the transitional flow in the pipe system. The numerical method used is a two-step variant of the Lax-Friedrichs method. Firstly, the non-dimensional form of governing equations is defined, then, the effect of Deborah and Reynolds numbers on pressure historic is investigated. The results revealed that increasing Deborah number, indicating the elasticity of the polymer, increases the oscillation height and consequently attenuation time of the transient flow becomes longer. It was also found that in low Reynolds, in a Newtonian fluid, line packing phenomenon effect is observed only at the first time period but in upper convected Maxwell fluid the effect of this phenomenon continues to more time periods and damping time becomes longer.

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.

In the present study, the sensitivity of the behavior of an Upper-Convected-Maxwell polymer and an Oldroyd-B fluid are compared to a Newtonian fluid. The governing equations are the Navier-Stokes equations and Viscoelastic fluid equations. These equations are non-dimensionalized and it is found that Reynolds and Mach numbers are only the dimensionless parameters that exists in all three mentioned fluids. The viscosity of fluids as a friction factor causes that Reynolds number and its changes play an important role in the oscillations and also the attenuation of the fluid transient during fluid hammer phenomenon. The numerical method used is a two-step variant of the Lax-Friedrichs (LxF) method. The results show that the Viscoelastic properties of fluids, such as the non-linear relationship of stress and strain, relaxation time and. . ., reduce their variability compared to Newtonian fluid. Finally, the maximum sensitivity to Reynolds variations in Newtonian fluid and the minimum amount is observed in the Upper-Convected-Maxwell polymer that there are strong Viscoelastic properties in its equations.

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.