results on jet stimulated by 302 Abstract We investigate the behaviour of a liquid jet stimulated by pressure disturbances using a photometric measurement of the jet shadow width. Two apparatuses involving lights of different nature are utilized and measurements are taken from the exit of the nozzle to drop breakoff for different operating conditions. Fourier analysis is applied to characterize the spatial evolution of the jet shape. In contrast to previous studies where only amplitudes of the Fourier modes are reported, phase shifts are also recovered for low and high initial perturbations. We show that the spatial reconstruction of the jet from the temporal Fourier analysis at different abscissae is in excellent agreement with the experimental profiles.
In this work, the influence of nozzle shape on microfluidic ink jet breakup is investigated. First, an industrial ink used in continuous inkjet (CIJ) printing devices is selected. Ink rheological properties are measured to ensure an apparent Newtonian behavior and a constant surface tension. Then, breakup lengths and shapes are observed on a wide range of disturbance amplitude for four different nozzles. Later on, ink breakup behaviors are compared to the linear theory. Finally, these results are discussed using numerical simulations to highlight the influence of the velocity profiles at the nozzle outlet. Using such computations, a simple approach is derived to accurately predict the breakup length for industrial CIJ nozzles.
The theory of the so-called Rayleigh–Plateau instability of fluid jets has been widely studied and can be used to predict the breakup length of liquid jets. Recently, in the work of Rosello et al. [J. Fluids Eng. 140(3), 031202 (2018)], the linear theory was enhanced to accurately predict the breakup length of continuous ink jets of Newtonian fluids by accounting for the influence of the nozzle geometry. In the present work, the influence of a shear-thinning behavior is addressed for both the breakup morphologies and breakup lengths in a linear regime. A comparison with the experimental data shows an excellent agreement extending the model of Rosello et al. to a non-Newtonian shear-thinning fluid.
For very low relaxation time (i.e. lesser than a microsecond) viscoelastic fluid experimental determination is difficult, if not impossible. In the present work the relaxation time measurement of a weakly elastic polymer solution, too low to be measured using classical rheometry techniques, is assessed using a mixed experimental-numerical strategy. First the fluid is rheologically assessed, by measuring its shear viscosity, surface tension and density. Then the relaxation time is determined by comparing the jetting of polymer solution from a Continuous Ink-Jet (CIJ) device experimentally and numerically. The numerical approach is first validated using test case and a viscoelastic Oldroyd-B model is then used to model the experimental solution. The relaxation time is then a parameter allowing us to fit numerical simulation onto experimental results. This mixed strategy is particularly convenient for weakly elastic solution for which physical parameters can not be measured using experimental rheometry setup.
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