The description of physical mechanisms involved in the impact of a drop upon a dry, partially wettable substrate is still a matter of debate. One way to analyze the balance of these mechanisms is the development of an analytical one-dimensional ͑1D͒ model based upon the energy equation. The assimilation of the drop to a cylinder allows a reduction of the energy equation to a second-order differential equation. This paper proposes a semi-empirical description of viscous dissipation taking into account the rolling motion near the contact line. The dissipation due to the rolling motion is added to the calculated dissipation in the core of the droplet. We compare our model to previous ones using a large set of literature data covering a wide range of viscosity, velocity impact, and equilibrium contact angle values. The new dissipation description proposed is shown to supersede those described in previous 1D models. Our model closely predicts the maximum spread factor and the time at which it is obtained on the whole range of Ohnesorge and Weber numbers considered. It also distinguishes between deposition with a steady variation in the wetted area from deposition with advancing and receding phases. The main limitations of the model lie in its inability to reproduce the spread factor at the very beginning of the impact and the rebounding observed after a receding phase for very high values of the equilibrium contact angle.

A series of monodisperse polybutadienes has been used to perform mechanical relaxation measurements from the flow regime to the glassy state. Results on loss shear moduli have been analyzed within the framework of a coupling model. It has been found to represent well the frequency dependence in the glassy and terminal zones using a segmental motion coupling parameter Pa and an entanglement coupling parameter Pv. Moreover, our results on apparent shift factors resulting from time-temperature superposition are consistent with the lack of thermorheological simplicity predicted by the coupling theory due to the difference between pa and &. ,

The experimental breakup of liquid jets subjected to a sinusoidal perturbation is investigated in the Rayleigh and first wind-induced regimes. Stroboscopic illumination of the jet and laser photometry method are used. The ability of linear spatial and temporal theories to describe certain aspects of the phenomenon is stressed. A review of data in the literature shows that the limited experimental windows investigated so far do not allow definite conclusions to be drawn. Our results, obtained over a wide range of fluid viscosity and jet velocity values, show that the linear theory of Sterling and Sleicher accurately predicts the variation in breakup length with jet velocity. The exponential character of the initial growth of a monochromatic perturbation along the jet is also described quantitatively. These results were obtained by carefully controlling the initial jet surface perturbation. It is also shown that transient surface tension and jet contraction have to be taken into account to analyze the experimental results.