Droplet - CFD Simulation CFD Software Tutorial

The Droplet tutorial serves as an introduction to SimFlow. In this tutorial, we will present the simulation of free free-falling droplet into the tank (geometry created directly in SimFlow). This simulation considers a 2D analysis of a multi-phase (water + air), incompressible flow.

SimFlow is a general purpose CFD Software

To follow this tutorial, you will need SimFlow free version, you may download it via the following link:
Download SimFlow

Open SimFlow and create a new case named droplet

We will start by creating a 2D mesh. This can be accomplished by choosing the Plate type as the background mesh.

We will start by creating a 2D mesh. This can be accomplished by choosing the Plate type as the background mesh.

Now we are ready to create our simple mesh.

After the meshing process is finished, the mesh should appear in the graphics window.

To indicate the initial shape of the droplet we will use cylinder geometry.

Additionally, we would like the droplet to fall down into the tank partially filled by water. To fill the bottom part of the domain with the water we will add another geometry.

To be able to better resolve water behavior, we will create an area with a higher mesh resolution. To do this, we will add two more box geometries.

The second refinement box will be located at the path of the falling droplet.

Check the refinement region by hiding the geometries and displaying mesh.

To analyze water behavior we will use Inter (interFoam) solver. This solver designed to model two-phase flow with interface capturing capabilities.

Now we will define the transport properties for both fluids.

Repeat this step for phase2 using air properties.

We will use the droplet geometry to select the region where water phase fraction should be initially applied.

Repeat the step for water geometry.

During calculation, we can observe intermediate results on a section plane. To add sampling data on a plane we need to define plane properties and also select variables that will be sampled. Note that runtime post-processing can only be defined before starting calculations and can not be changed later on.

For any simulation, it is very convenient to let the solver automatically determine the proper time step value. To use this option we need to define time step constraints by providing the initial time step(adjusted by the solver during computations), maximal time step value and the Courant number. In our case, we will reduce the default Courant number for better stability and quality.

It is very important to control when results should be stored on the hard drive. This is especially important for the transient simulations where users are interested in the whole flow history saved as a collection of the snapshots.

When calculations will begin SimFlow automatically will switch view to the Residuals tab, where we can observe the convergence of our simulation. This is very handy for steady-state simulations when we try reaching low residuals levels. In case of transient simulation, we would rather like to see how our flow develops as simulation time progress.

This concludes the tutorial, covering all the aspects we intended to showcase. To create a finely tuned presentation of the results, you may take advantage of the seamless integration with ParaView. You can easily open simulation results in ParaView with a single click from SimFlow.

In ParaView, you can perform typical and advanced postprocessing tasks such as displaying streamlines, contour plots, vector fields, line or time plots, and calculating volume or surface integrals.

To familiarize yourself with the ParaView capabilities, it’s worth checking out our video tutorial, Paraview CFD Tutorial - Advanced Postprocessing in ParaView, in which we demonstrate some of the most commonly used post-processing techniques.

Paraview CFD Tutorial - Advanced Postprocessing in ParaView