ANSYS Fluent: Multiphase VOF Inkjet Droplet Generation | Tutorial

[@cfdkareem]

Hello! I've added the pressure profile to the description of this video if you would like to try it out yourself!

[@NEMZEFILL]

Dude u beast, I’m searching guides like this one for weeks, simple and informative plus u explain ui of program and what it does

[@cfdkareem]

Glad you found it helpful!

[@sahrahamdollahi6725]

Thanks for the video

[@AbrarGASMI-dy6yf]

Hello sir, thanks for this nice tutorial. Can you please provide us with the geometry details ?

[@af2825]

Hello Sir, first of all I would like to thanks you for nice tutorial. Can you please upload one tutorial, in which water droplet absorption and spreading behaviour in porous surface?

[@cfdkareem]

Hello, thanks for the suggestion! This is a topic I have been working on currently. I will create a tutorial when I have a working model. Stay tuned...

[@AdityaChivate]

Hello! Thank you for the amazing tutorial. Can you please share how you created the pressure profile? I am want to create a pressure profile from some input parameters (for a piezo inkjet nozzle). It would be great if you can refer me to some existing work that discusses more about this relation

[@cfdkareem]

Hello, the pressure profile is in the video description!

[@AdityaChivate]

I used that pressure profile, I wanted to know how was that generated? Do you have any reference literature so that I can modify that pressure profile according to my operating conditions. Thank you!

[@cfdkareem]

@AdityaChivate this pressure profile is just an arbitrary waveform for the purpose of the tutorial unfortunately. If you look through some literature on inkjet waveform generation you may be able to copy a representative one from the literature.

[@AdityaChivate]

@@cfdkareem Thanks for your reply. I'll check around to see if there's any existing literature that talks about this.

[@bassiakosjr]

Hello and thanks for sharing this enlightening tutorial and power point presentation. I was wondering if you could answer two questions that I came up with while watching this video. 1) does the CFL criterion apply to the implicit time integration scheme as well, especially when using adaptive step stepping (the adaptive time stepping in the "Run Calculation" tab for implicit VOF remains unchanged asking again for a Global Courant Number). 2) when using the mixture model, in general, do we need a mesh of similarly fine quality to the VOF (or Eulerian model) since we're not capturing the interface position? I would really appreciate your thoughts. Thank you in advance.

[@cfdkareem]

1) If you are using the implicit scheme you can usally relax the CFL number to 5 or 10. Using the implicit scheme is only recomened if you are interested in the final steady state result, not the intermidiate transient flow states. 2) I don't like making general statements, but yes, on average, the mesh accuracy can be relaxed when using the mixture model. You will need to max sure that your mesh is still capturing your flow characterisitcs correctly.

[@bassiakosjr]

@@cfdkareem thank you so much for your prompt response.

[@agnimitraghosh9421]

Can you please share the pressure profile for the study.

[@cfdkareem]

Definetly! I just added the profile to the description of the video. Copy the profile to a text document and save it as a .txt file. You can then read it into Fluent for the study. Thanks!

[@agnimitraghosh9421]

@@cfdkareem thank you. It helped a lot!

[@priyapalanivel3907]

Thanks for such a great tutorial. Firstly, Would you please let me know how you got the pressure inlet profile? In my case actually, I have a voltage pulse profile, but I am not sure how to convert it from voltage to pressure profile. Any methods to find this pressure profile. Secondly, I couldn't find the geometry details that you have used for this tutorial, would you provide it in a detailed manner like nozzle inlet dia, throat dia along with the air chamber width.

[@cfdkareem]

Hello, going from voltage to pressure requires an initial simulation that models the piezo movement. I obtained this profile from such a simulation. To model this you will have to model the whole ink chamber. You can do this with a single phase simulation and have a pressure=0 condition at the outlet. You will then input the voltage profile to drive the motion of the piezo and export the pressure generated right above the nozzle. I will add such a model to my future video list!

[@life_is_boring2000]

where can i find dimensions for this nozzle????

[@cfdkareem]

Hello, I mentioned it in the video, but didn't list it. The nozzle diameter is 100um with a 100um bore.

[@JosueLopez-ft4lq]

How could I apply this to a solder reflow simulation, with a 3d model? could you please help me. Thank you!!

[@cfdkareem]

Hey Josue, 3D VOF models are very computationally intensive so if you can reduce your model to a 2D axis symmetric or 2D planer it will be much simpler. I have a video coming out soon on the deposition and solidification of a metal droplet on a solid substrate. It may help give you some direction for your model!

[@murtadhaidan7714]

please my work about how is inkjet droplet of binder to powder in binder jetting

[@cfdkareem]

Hello, I have a video coming out soon on deposition of droplets on a substrate which may help you. For binder jetting you can do one of two things. First, you can try depositing droplets onto a "porous media" which will use a mathematical approximation for the wetting of the ink into the powder. Second, much more complex, you can create a STL file of a small region of powder and deposit the droplet on top. This will require a very high fidelity 3D mesh and will be a complex model. What question are you trying to answer with your model? This will help me provide a better answer your question. Thanks!

[@adele_90]

In 2023 version, I don't see "phases" tab under "physics" section.

[@cfdkareem]

Hello Adele, in 2023 you can find the "Multiphase" option under Physics>Models from the top toolbar, or Setup>Models>Multiphase under the outline view.