# Film Separation Modeling ANSYS Fluent

## Simulation of Film Separation at backward facing step

In this tutorial, we provide guidelines for modeling and simulation of film separation using Eulerian Wall Film (EWF) model. We use backward facing step problem in this tutorial. This method can be utilized to analyze the ability of turbulence models for the prediction of separated flows & reattachment.

### EWF model and Film Separation Modeling

We employ EWF model to predict the formation and flow of thin liquid films on wall surfaces.

### It is possible to use this model with:

• Discrete Phase Model – In this case, particles aggregate on the wall to form the film
• Eulerian Multiphase Model –In this case, the film is formed on the wall by secondary phase mass

EWF model uses a virtual film on the surface instead of mesh normal to the surface. The focus of thin film modeling is to model a thin film flow which can separate, strip and evaporate without affecting the core flow-field. Thin film modeling with these characteristics is computationally expensive. Because we need to use very fine mesh and calculate inter-phase flux accurately.

We can also use EWF model with the 3d solver. This model assumes that film always flows parallel to the surface and therefore the normal component of film velocity is zero. In addition, The film has a parabolic velocity profile & bilinear temperature profile across its depth.

### Problem Description of Film Separation

Here we model the creation of a water film due to the impingement of water particles. Air flows through the inlet and we inject water particles upstream of the backward facing step. We employ Euler film model to simulate the film formation and detachment at the edge of the step. Particles aggregate on the wall forming the film. At the edge, the film separates and release the particles. Separated particles get recollected on the downstream bottom wall.

### You will also learn how to do the following through this tutorial:

• Creating a film by couple EWF model with Eulerian multiphase approach
• Modeling detachment of film at edge
• Modeling film heat transfer