Published online by Cambridge University Press: 06 August 2019
Normal and oblique drop impact on a solid surface is numerically analysed for yield stress fluids. A rich diversity of results are generated as a consequence of the exploration of the inertial, elastic, plastic and thixotropic features of the process, as well as the inclination of the solid surface. We show that drops of more thixotropic fluids have a higher tendency to bounce in the normal impact, and to roll or to bounce in the case of an oblique drop impact. Concerning elasticity, we found a critical value for the elastic Ohnesorge number above which no bouncing takes place. Experimental findings such as the fact that the stored energy due to the elasticity of the fluid drop plays a role similar to the stored energy of an interfacial nature in inelastic fluid drops are corroborated in the present study.
Numerical prediction of the structure parameter $\lambda$ at different dimensionless times using $Re=2.05$, $\tau_y=0.7$. From (column) left to right: $t_{eq}=5, 20$, and from (row) top to bottom: $Wi=0.05, 2$. The reader will find, in the supplementary material, the file Movie1.mp4 with the movie of the evolution displayed in this figure.
Numerical predictions of the structural parameter $\lambda$ at different dimensionless times using $Re=13.49$, $\tau_y=0.7$ and $Wi=0.5$ or $2.0$. Columns from left to right: $t_{eq}=5, 20$. The reader will find in the supplementary material the movie with the complete evolution of the motions shown in this figure.
Drop interface profiles for a surface at an inclination of $\theta=30 \degree$. The fixed non-dimensional parameter for the EVPT material is $Wi=0.05$; The thixotropic times shown are $t_{eq}=1, 5, 20$
Drop interface profiles for a surface at an inclination of $\theta=30 \degree$. The fixed non-dimensional parameter for the EVPT material is $Wi=2$; The times shown are $t_{eq}=1, 5, 20$. The drop interface profiles considering an Oldroyd-B fluid with $Wi=2$ for different $Re$ are also included
Numerical prediction of the structural parameter $\lambda$ at different dimensionless times using $Re=13.49$, $\tau_y=0.7$, $t_{eq}=5,$ and $Wi=0.5$ for a surface at an inclination of $\theta=30 \degree$. The reader will find, in the supplementary material, the file Movie5.mp4 with the movie of the complete evolution of the case shown in this figure.
Numerical prediction of the structural parameter $\lambda$ at different dimensionless times using $Re=13.49$, $\tau_y=0.3$, $t_{eq}=20,$ and $Wi=0.5$ for a surface at an inclination of $\theta=30 \degree$. The reader will find, in the supplementary material, the file Movie6.mp4 with the movie of the complete evolution of the case shown in this figure.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Normal impact, Re=2.05, Wi=0.05.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Normal impact, Re=2.05, Wi=2.00.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Normal impact, Re=13.49, Wi=0.05.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$.Normal impact, Re=13.49, Wi=2.00.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=2.05, Wi=0.05.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=2.05, Wi=2.00.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $\tau_y=0.1$ and $t_{eq}=5$. In the right column, $\tau_y=0.7$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=13.49, Wi=0.05.
Set of evolutions with plastic number and dimensionless thixotropic time fixed. In the left column, $ au_y=0.1$ and $t_{eq}=5$. In the right column, $ au_y=0.7$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=13.49, Wi=2.00.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Normal impact, Re=2.05, $\tau_y$=0.1.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Normal impact, Re=2.05, \tau_y=0.7.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Normal impact, Re=13.49, \tau_y=0.1.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Normal impact, Re=13.49, \tau_y=0.7.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=2.05, \tau_y=0.1.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=2.05, \tau_y=0.7.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=13.49, \tau_y=0.1.
Set of evolutions with Weissenberg and dimensionless thixotropic time fixed. In the top left position, $Wi=0.05$ and $t_{eq}=5$. In the top right position, $Wi=0.05$ and $t_{eq}=20$. In the bottom left position, $Wi=2.00$ and $t_{eq}=5$. In the top right position, $Wi=2.00$ and $t_{eq}=20$. Inclined plane, $30^0$, Re=13.49, \tau_y=0.7.