Research Topic

Droplet Impact on Porous Media


example of a porous substrate (Source: wikipedia)

A droplet impact on a porous substrate is a an important phenomena for many industrial applications like Ink-Jet-Printing, irrigation, droplet cooling or needle free injections. Thereby one is interested in the penetration depth and spread-factor into the substrate or the behavior of the droplet during the impact.

Currently mostly 2D simulations with a modeled porous substrate have been presented. In this work , full 3D simulations with resolved capillaries and appropriate boundary conditions of the rigid bodies in the substrate shell be performed. With this results it will be possible to predict the outcome of the mentioned phenomena in a detailed way.

Numerical Methods

Porous substrates in numerical simulations are often modeled as source term in the Navier-Stokes-Equations. With a known permeability of the substrate one can simulate a quantitative intrusion. The aim of this work is to resolve the capillary tubes of the substrate in order to make predictions of the penetration depth and speed of droplet in a more detailed way.

One general approach for simulating a free surface flow is the Volume-of-Fluid (VoF) method. Here one solves besides the Navier-Stokes-Equations an additional transport equation for a phase indicator. As the geometry of a porous substrate can be very complex, in this work the Immersed-Boundary-Method (IBM) will be applied. This method uses a (cartesian) non body-conformal mesh whereas the geometry is provided by an external surface mesh. In order to imply the influence of the boundary at the solid surface, one introduces an additional Immersed-Boundary-Force which only acts close to the solid surface. In the Discrete-Forcing-Approach this force is applied after the discretisation of the equations and the value of the cells close to the surface are interpolated by the use of its neighbors and the value of the boundary close to the cell-center. Using this method a simulation of complex geometries will be possible.

Physical models

The behavior of a droplet impact is still under research. An important topic in this field is the propagation of the contact-line and the related contact-angle. Several models have been developed in order to predict the movement correctly. The basic phenomena take place on a molecular level which is not resolved in the simulations. Therefore one has to find appropriate models for a correct prediction of the propagation.


The scope of this topic is an accurate simulation of a droplet impact on a porous media. The next steps towards this goal are:

  • Extending the IBM to 3D and free surface flows
  • validation of the IBM
  • Validation and Extension of the contact-line models
  • Analysis of droplet impacts on porous media

Key Research Area

Multi-Physics, Multiphase Flows, Free Surface Methods, Immersed Boundary Method


Nicklas Linder


Dolivostraße 15

D-64293 Darmstadt



+49 6151 16 - 24401 or 24402


+49 6151 16 - 24404




linder (at) gsc.tu...

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