Study of non-orthogonal time dependent mixed convection Hiemenz flow of viscoelastic Walter's B fluid with thermal radiation is the major focus of this article. The surface intact with the fluid particle is assumed to be oscillating-stretching and heated with sinusoidal surface temperature. This physical process is modeled in mathematical form into system of PDEs, which are simulated numerically by Chebyshev spectral method. The obtained solution is firstly validated for reduced case with already published results, and then further results are achieved for governing physical parameters. The effects of dimensionless emerging constants are described through tables and graphs. In this study, it is concluded that in assisting flow case velocity enhances as compared to opposing flow case. By increasing the Weissenberg number velocity of the fluid decreases in both assisting and opposing flow cases while in opposing flow case these effects are more prominent as compared to assisting flow case. The streamlines in both assisting and opposing flow cases come closer to each other with the passage of time and at t = 3π / 2, they overlap each other and stagnation points also get coincide.
We examined elongational flows into small apertures for dilute aqueous solutions of polymers: Polyethlene Oxide (PEO-18) and Polyacrylamide (PAA). The elongational stress (τzz) was found by applying momentum flux equation to be expressed as τzz = ρv2, where ρ is the density, v is the local velocity at an elongational position along the center line of the flow. We solved continuity equation by assuming both “thread-like fluid region” for the region of elongational flow and simple two types for the velocity normal to the thread, and found the two types for the elongational flow velocity: (a) linear increase in the elongational flow velocity as approaching the aperture and (b) similarly but exponential increase. We found that (a) agreed with the velocity distribution for PEO-18 solution, and (b) for PAA solution.
Although the Rouse model has been widely used to describe unentangled polymer dynamics, there are some experimental and simulation results, in which the local chain dynamics is not fully consistent with the Rouse predictions. In this study, molecular simulations by a few different molecular models were conducted to reveal the effects of inter-molecular interactions on the relaxation of Rouse modes. Kremer-Grest bead-spring simulations exhibited that the second and third Rouse modes relaxations deviate from the Rouse prediction even though the first Rouse mode relaxation is fairly consistent with the Rouse behavior. A similar deviation was observed for full-atomistic simulations of polybutadiene and polyisoprene. For dissipative particle dynamics simulations, the magnitude of deviation was much smaller. Additional Kremer-Grest simulations with various molecular weights and full-atomistic simulations without excluded volume interactions suggest that the chain rigidity and the hard-core inter-beads interactions are attributable to the deviation through short-time relaxations induced by inter-beads collisions.
Mechanical/rheological properties of single viable cells were investigated by squeezing tests. Human oral keratinocytes were harvested from oral mucosa tissue sample, grown in a culture medium with two different calcium ion concentrations. The cells were squeezed between a convex lens and a flat plate until reaching the crushed state. The extension ratio, determined by the diameter at destruction relative to the initial diameter, was evaluated, and cell destruction patterns were classified. The extension of cells was reduced when they were cultured in the culture medium with a higher calcium ion concentration. The cell destruction patterns observed were classified into two types corresponding to the membrane rupture style. Our results indicated that cells cultured with a higher calcium ion concentration typically show a destruction pattern characterized by cell surface rupture at several parts. Moreover, the incidence ratio of the destruction patterns was highly correlated with the extension ratio of the cells.
Variation of dynamic shear modulus, G* = G′ + iG″, was measured for glassy poly(methyl methacrylate) (PMMA) during uniaxial stretching processes where the tensile rate changed stepwise. Under the condition of constant-rate stretching, it is known that G′ and G″ gradually change to their steady values in the post-yield range of strain, and that the change occurs strongly at a higher tensile rate, indicating strain-induced changes in glassy structures. After a change of tensile rate, G′ as well as G″ varied monotonously from their values at the initial tensile rate to those at the final rate in a strain range where the uniaxial stress σ exhibited transient responses to the tensile rate change. The observed variation of G′ and G″ simply indicates that, after an abrupt change of tensile rate, structures of the glass successively change from those corresponding to initial tensile rate to final rate.