Multi-scale analysis of a viscoelastic liquid jet

Abstract

A multi-scale analyzing tool is now available to investigate the temporal evolution of two phase flows such as liquid systems experiencing an atomization process. Thanks to its multi-scale and global nature, it allows identifying all dynamics simultaneously involved in the process with no restriction of the liquid system shape. In the present work this multi-scale tool is applied on 2D visualizations of free falling jets of a low-viscosity viscoelastic solution. The jets are produced from a cylindrical discharge orifice and the liquid is a very dilute polymer solution containing 5 PPM of Poly(ethylene oxide). High spatial resolution images of the free falling jets are performed as a function of the velocity and at several distances from the discharge orifice. For every operating condition, the liquid jet remains cylindrical first, then shows the development of a sinusoidal perturbation and finally adopts a beads-on-a-string pattern before breakup occurs. The multi-scale analysis is performed on a high number of images and at several spatial positions in order to return statistical and temporal information, respectively. The results of this analysis show that during the sinusoidal perturbation stage, the large-scale region follows an exponential increase as predicted by the linear stability theory and during the beads-on-a-string

Behaviour of free falling viscoelastic liquid jets

“…This work completes a previous experimental study of the behaviour of free-falling liquid jet of dilute viscoelastic solutions [1]. This study considered the dynamic at small scales that was detected by applying a 2D multi-scale description of the jets and identified an exponential decreasing regime from which the viscoelastic relaxation time of the solution could be measured.…”

“…Until recently, new results [4] suggest that an operating domain where these dependences vanish may exist. In this context, a multi-scale analysis of the behaviour of free falling jets of a dilute viscoelastic solution was performed, allowing measurements of the relaxation time [1]. The dynamics of the smaller scales was monitored and an exponential decrease was observed from which a relaxation time was extracted.…”

“…The temporal evolution of d1 for the free viscoelastic jets reported a decrease according to three regimes [1]. The second one is an exponential regime which corresponds to an elastic-controlled capillary thinning behavior [1], i.e. :…”

“…

AbstractIn a recent work, a protocol to measure the relaxation time of dilute polymer solutions, known to be challenging, has been established [1]. This protocol is based on a 2D multi-scale description of free-falling low velocity viscoelastic liquid jets.

…”

“…The analysis of these images used a 2D multi-scale description of the jet. This description consisted in measuring the surface-based cumulative scale function E2(d,z) as a function of the position z (see [1]). First, image treatments were applied to provide two-level images where the liquid appeared as black pixels on a white background.…”