For more than 20 years it has been debated if yield stress fluids are solid below the yield stress or actually flow; whether true yield stress fluids exist or not. Advocates of the true yield stress picture have demonstrated that the effective viscosity increases very rapidly as the stress is decreased towards the yield stress. Opponents have shown that this viscosity increase levels off, and t...

The unsteady two-dimensional flow of a viscoelastic second-grade fluid impinging on an infinite plate is considered. The plate is making harmonic oscillations in its own plane. A finite difference technique is employed and solutions for small and large frequencies of the oscillations are obtained. 1. Introduction. In the past two decades, the importance of non-Newtonian viscoelastic liquids hav...

We study the retraction and pinch-off of a liquid filament and the formation of drops by using an energetic variational phase field model, which describes the motion of mixtures of two incompressible fluids. An efficient and accurate numerical scheme is presented and implemented for the coupled nonlinear systems of Navier–Stokes type linear momentum equations and volume preserving Allen–Cahn ty...

The shear free condition is studied for dissipative relativistic self–gravitating fluids in the quasi–static approximation. It is shown that, in the Newtonian limit, such condition implies the linear homology law for the velocity of a fluid element,only if homology conditions are further imposed on the temperature and the emission rate.It is also shown that the shear–free plus the homogeneous e...

The molecular structure of fluids composed of dendrimers of different generations is studied using nonequilibrium molecular dynamics (NEMD). NEMD results for dendrimer melts undergoing planar Couette flow are reported and analyzed with particular attention paid to the shear-induced changes in the internal structure of dendrimers. The radii of gyration, pair distribution functions and the fracta...