EXP 1-4 Measurement Data and Results: Difference between revisions
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The drop-film interaction in the three videos from Table 1 (see Section [[Lib:EXP 1-4 Description]]) can be characterized as follows. | The drop-film interaction in the three videos from Table 1 (see Section [[Lib:EXP 1-4 Description]]) can be characterized as follows. | ||
* For the '''low energy impact''' the drop joins the liquid film smoothly without formation of a rim or crown. In this ''deposition regime'', the drop spreads on the surface of the liquid film forming a disk-shaped structure. In the late stage, capillary waves propagate on the surface of the film without formation of a notable central dome. | |||
For the '''moderate energy impact''' a rising crown is formed at the boundary between the residual and the initial film where there is a kinematic discontinuity due to the jump in both the film thickness and the local velocity field. The crown ascend continues as long as the inertial forces dominate the surface tension forces. The upper free rim of the crown remains stable and fully axisymmetric and the case corresponds to the ''crown formation without break-up regime''. In the late stage after collapse of the crown, a dome like structure forms at the impact center without generation of a jet. | For the '''moderate energy impact''' a rising crown is formed at the boundary between the residual and the initial film where there is a kinematic discontinuity due to the jump in both the film thickness and the local velocity field. The crown ascend continues as long as the inertial forces dominate the surface tension forces. The upper free rim of the crown remains stable and fully axisymmetric and the case corresponds to the ''crown formation without break-up regime''. In the late stage after collapse of the crown, a dome like structure forms at the impact center without generation of a jet. | ||
Revision as of 08:51, 10 August 2023
Axisymmetric drop impact dynamics on a wall film of the same liquid
Measurement data/results
The drop-film interaction in the three videos from Table 1 (see Section Lib:EXP 1-4 Description) can be characterized as follows.
- For the low energy impact the drop joins the liquid film smoothly without formation of a rim or crown. In this deposition regime, the drop spreads on the surface of the liquid film forming a disk-shaped structure. In the late stage, capillary waves propagate on the surface of the film without formation of a notable central dome.
For the moderate energy impact a rising crown is formed at the boundary between the residual and the initial film where there is a kinematic discontinuity due to the jump in both the film thickness and the local velocity field. The crown ascend continues as long as the inertial forces dominate the surface tension forces. The upper free rim of the crown remains stable and fully axisymmetric and the case corresponds to the crown formation without break-up regime. In the late stage after collapse of the crown, a dome like structure forms at the impact center without generation of a jet.
The case of the high energy impact corresponds to the crown formation without break-up regime as well. However, the increased magnitude of inertial forces causes the crown to grow much higher (approximately twice) as compared to the moderate energy impact. While the upper free rim remains axisymmetric during the ascend of the crown, slight deviations from axisymmetry can be noticed during the collapse of the crown. Moreover, the energy of the impact is high enough to form a central Worthington jet which emerges from the impact center. The central jet experiences rupture (pinch-off) and forms satellite droplets. These droplets bounce on the surface of the disturbed film before merging into it.
Excel files with experimental results for moderate and high impact velocity are available for download through the website https://tudatalib.ulb.tu-darmstadt.de/handle/tudatalib/3295 or via the following doi: https://doi.org/10.48328/tudatalib-722. In addition to the experimental results, the Excel files also include results of numerical simulations with a phase-field method. The content of the Excel files is described below.
In the numerical simulations, two different models for the surface tension force (equilibrium/relaxation) are employed in combination with different spatial resolutions. In the phase field method, the surface tension force is related to the profile of the phase-discriminating order parameter (C) and depends in particular on the gradient of C within the diffuse interface region. In the standard (equilibrium) formulation, C is assumed to follow the tanh profile of the equilibrium state whereas the relaxation model accounts for the deviation of the actual profile of C from the equilibrium profile. The spatial resolution is quantified by the number of mesh cells Nc used to resolve the diffuse interface as illustrated in Fig. 6.
Fig. 7 compares experimental results for the three crown dimensions (base diameter, rim diameter, crown height) with numerical results obtained for the two surface tension models and different grid resolution for the case with moderate impact energy. In contrast to the equilibrium model for surface tension, the relaxation model is able to reproduce the experimental data with reasonable accuracy irrespective of the number of interfacial cells. The Excel file for this case includes one worksheet for each of the six subfigures of Fig. 7. Each of the six worksheets contains one column for time, one column for the respective measured (experimental) crown dimension and four columns for the respective numerical results obtained with the different resolutions.
A similar Excel file is provided for the case with high impact energy (see links in first paragraph above). A figure similar to Fig. 7 for the high energy impact can found in the reference below, which also gives more detailed discussions of the experimental and numerical results and conclusions drawn.
M. Bagheri, B. Stumpf, I.V. Roisman, C. Tropea, J. Hussong, M. Wörner, H. Marschall, Interfacial relaxation – Crucial for phase-field methods to capture low to high energy drop-film impacts, Int. J. Heat Fluid Flow 94 (2022) 108943, https://doi.org/10.1016/j.ijheatfluidflow.2022.108943
Contributed by: Milad Bagheri, Bastian Stumpf, Ilia V. Roisman, Cameron Tropea, Jeanette Hussong, Martin Wörner, Holger Marschall — Technical University of Darmstadt and Karlsruhe Institute of Technology
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