arXiv subjects

J. A. Dijksman

Publications and source records attributed to J. A. Dijksman.

3 recordsLinked to original sources

arXiv2021

Instabilities of a thin liquid film in a funnel

We explore flow of a completely wetting fluid in a funnel, with particular focus on contact line instabilities at the fluid front. While the flow in a funnel may be related to a number of other flow configurations as limiting cases, understanding its stability is complicated due to the presence of additional azimuthal curvature, as well as due to convergent flow effects imposed by the geometry. Convergent nature of the flow leads to thickening of the film, therefore influencing its stability properties. In this work, we analyze these stability properties by combining physical experiments, asymptotic modeling, self-similar type of analysis and numerical simulations. We show that appropriate long-wave based model supported by the input from experiments, simulations and linear stability analysis origination from the flow down an incline plane provides a basic insight allowing to understand the development of contact line instability and emerging lengthscales.

physics.flu-dyn↗

arXiv2011

Jamming, Yielding and Rheology of Weakly Vibrated Granular Media

We establish that the rheological curve of dry granular media is non-monotonic, both in the presence and absence of external mechanical agitations. In the presence of weak vibrations, the non-monotonic flow curves govern a hysteretic transition between slow but steady and fast, inertial flows. In the absence of vibrations, the non-monotonic flow curve governs the yielding behavior of granular media. Finally, we show that non-monotonic flow curves can be seen in at least two different flow geometries and for several granular materials.

cond-mat.soft↗

arXiv2010

The role of tap duration for the steady state density of vibrated granular media

We revisit the problem of compaction of a column of granular matter exposed to discrete taps. We accurately control the vertical motion of the column, which allows us to vary the duration T and the amplitude A of single-cycle sinusoidal taps independently. We find that the density of the material at the reversible branch depends both on A and T. By comparing the densities on the reversible branches obtained for a range of values of T, we find that we can collapse all data when plotted as function of A/T, which scales similar to both the liftoff velocity and the time of flight of the packing. We further show that switching between states obtained for different A and T, but chosen such that their densities on the reversible branches match, does not lead to appreciable hysteresis. We conclude that the appropriate control parameter for sinusoidal tapping is not the peak acceleration Γ\sim A/T^2, as is usually assumed, but rather ΓT \sim A/T.

cond-mat.soft↗