We propose a hybrid continuum surface tension force (CSF) formulation to model the interface interaction within the three-phase volume of fluid (VOF) method. Instead of employing the height function ...globally, we compute the curvature based on a smooth fraction function near the region of the triple contact point. In addition, we apply the isotropic finite difference method to calculate derivatives, and the current scheme readily accommodates adaptive mesh refinement, greatly enhancing efficiency. We rigorously validate the hybrid CSF using two benchmark problems that have received limited attention in previous studies of the three-phase VOF method. Using the hybrid CSF method, we accurately predict the behavior of a liquid lens under specific surface tension ratios. Furthermore, the simulation results of the equilibrium morphology of two contacting droplets are consistent with the theoretical expectations.
•Hybrid continuum surface tension force.•Three-dimensional and three-phase VOF method.•Benchmark validations for three-phase VOF method.
A well-known drawback of the Volume-Of-Fluid (VOF) method is that the breakup of thin liquid films or filaments is mainly caused by numerical aspects rather than by physical ones. The rupture of thin ...films occurs when their thickness reaches the order of the grid size and by refining the grid the breakup events are delayed. When thin filaments rupture, many droplets are generated due to the mass conserving properties of VOF. Thus, the numerical character of the breakup does not allow obtaining the desired convergence of the droplet size distribution upon grid refinement. In this work, we present a novel algorithm to detect and perforate thin structures. First, thin films or ligaments are identified by taking quadratic moments of an indicator obtained from the volume fraction. A multiscale approach allows us to choose the critical film thickness independently of the mesh resolution. Then, the breakup is induced by making holes in the films before their thickness reaches the grid size. We show that the method improves the convergence upon grid refinement of the droplets size distribution and of enstrophy.
A well-known drawback of the Volume-Of-Fluid (VOF) method is that the breakup of thin liquid films or filaments is mainly caused by numerical aspects rather than by physical ones. The rupture of thin ...films occurs when their thickness reaches the order of the grid size and by refining the grid the breakup events are delayed. When thin filaments rupture, many droplets are generated due to the mass conserving properties of VOF. Thus, the numerical character of the breakup does not allow obtaining the desired convergence of the droplet size distribution under grid refinement. In this work, we present a novel algorithm to detect and perforate thin structures. First, thin films or ligaments are identified by taking quadratic moments of an indicator obtained from the volume fraction. A multiscale approach allows us to choose the critical film thickness independently of the mesh resolution. Then, the breakup is induced by making holes in the films before their thickness reaches the grid size. We show that the method improves the convergence upon grid refinement of the droplets size distribution and of enstrophy.
We propose a hybrid continuum surface force (CSF) formulation to model the interface interaction within the three-phase volume of fluid (VOF) method. Instead of employing the height function ...globally, we compute the curvature based on a smooth fraction function near the region of the triple contact line. In addition, we apply the isotropic finite difference method to calculate derivatives, and the current scheme readily accommodates adaptive mesh refinement, greatly enhancing efficiency. We rigorously validate the hybrid CSF using two benchmark problems that have received limited attention in previous studies of the three-phase VOF method. Using the hybrid CSF method, we accurately predict the behavior of a liquid lens under specific surface tension ratios. Furthermore, the simulation results of the equilibrium morphology of two contacting droplets are consistent with the theoretical expectations.
This study analyzes and compares party ads that were broadcast on television during the 2009 European Election campaign in France, Germany, Sweden and the UK. Even though electoral TV ads have never ...reached the same importance in European countries as in the US, such ads are to be regarded as an expression of the specific political culture of a country and therefore have relevance beyond election campaigns. An international comparison of ads produced for the same event is particularly suited to revealing similarities across cultures as well as national idiosyncrasies. Additionally, the present study demonstrates a methodological approach that defines a 'sequence' as the unit of analysis instead of the whole spot, and thus it is different from previous research on electoral advertising.
Advertising for Europe Holtz-Bacha, Christina; Johansson, Bengt; Leidenberger, Jacob ...
Nordicom review,
12/2012, Volume:
33, Issue:
2
Journal Article
Peer reviewed
Open access
This study analyzes and compares party ads that were broadcast on television during the 2009 European Election campaign in France, Germany, Sweden and the UK. Even though electoral TV ads have never ...reached the same importance in European countries as in the US, such ads are to be regarded as an expression of the specific political culture of a country and therefore have relevance beyond election campaigns. An international comparison of ads produced for the same event is particularly suited to revealing similarities across cultures as well as national idiosyncrasies. Additionally, the present study demonstrates a methodological approach that defines a ‘sequence’ as the unit of analysis instead of the whole spot, and thus it is different from previous research on electoral advertising.
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