Inquiry regarding UEq vs. PUEq for Shock-Induced Cavitation

[vitamilk-codo]

Dear ECOGEN Developers,

I am a graduate student from Harbin Engineering University (HEU), China. My current research focuses on the interaction between shock waves and liquid droplets.

First of all, I would like to express my sincere respect and gratitude to you and your team. ECOGEN is a remarkably powerful CFD tool that has been immensely helpful to my research. Before discovering your code, I attempted to simulate these phenomena using ANSYS Fluent, but the results were unsatisfactory. I am now a strong advocate for ECOGEN and have been recommending it to my colleagues and supervisor.

Despite the excellent performance of the code, I have encountered a specific technical challenge that I hope you could clarify:

1. Model Selection for Cavitation:
   I noticed that the shock-induced cavitation cases in your official library utilize the UEq (Velocity Equilibrium) model. I am curious about the rationale behind choosing UEq over the PUEq (Pressure-Velocity Equilibrium/Kapila) model for these specific cavitation problems.

2. Oscillations in Internal Pressure:
   I conducted a comparative study between your library case (UEQ/2D/dropletShockInducedCavitation/Mach2.4) and my own test using the PUEq model (Mach 1.5 shock on a 2mm water droplet).

While the overall droplet deformation and shock wave evolution appear similar between the two, the internal pressure evolution captured by my probes is significantly different. Specifically, my PUEq results exhibit high-frequency oscillations inside the droplet (as shown in the attached images).

Question: What might be causing these severe pressure oscillations in my PUEq simulation? Could it be related to the absence of pressure relaxation settings in my current configuration?

I have attached my configuration files (Main.xml, Model.xml, and initialConditions.xml) and the probe comparison plots for your reference.

Thank you very much for your time and for providing such an outstanding open-source tool to the community. I look forward to your insights.

enclosure.docx

[NiruBhai]

Hi, I am a fellow user, not associated with the developers. I think this article by them would help though: https://doi.org/10.1002/fld.5142
Modelling interactions between waves and diffused interfaces

[kevinschmidmayer]

Hello @vitamilk-codo

First, thank you for your kind message. We are always very happy to hear the code helps others in their research projects.

Second, thank you @NiruBhai. I would add that reading this other paper will help answer your questions: https://doi.org/10.1063/5.0127105
After reading this, if this is still unclear to you. Please get back to us and I'll try my best to make an elaborate answer.

Best,
Kevin

[vitamilk-codo]

thanks a lot @NiruBhai @kevinschmidmayer
I will read these two articles carefully, Sorry for the delayed response due to the time difference.
besides, as a new graduate student just beginning my journey in this field, I have a few broader questions regarding the research trends:
Research Frontiers: It seems that traditional studies on shock-droplet interaction have largely focused on external mechanisms, such as breakup modes (bag, stripping, etc.) or surface instabilities (KH, RT). Is the study of internal cavitation currently considered a frontier or cutting-edge topic in this community? It feels like it adds an essential internal dimension to the classical aerobreakup theory.
Future Directions: Given the impressive work your team has done with ECOGEN, I was wondering if your group plans to continue research in the droplet direction? As I am still building my knowledge base, understanding the future roadmap of leading teams like yours would be incredibly inspiring.