Troubleshooting Patchy Water Film in Discrete Phase Model (DPM) Coupled with Eulerian Wall Film (EWF) CFD

 There are a few possible reasons why  cloud map might be showing a granular distribution for the water film thickness when using a coupled DPM-EWF model:

1. Particle Size Discretization: In the DPM, you likely define a range of particle sizes to represent the water droplets. This discretization can lead to a blocky or granular appearance in the cloud map, especially if the range is large or the number of size classes is small.

2. Limited Resolution: Cloud maps often have a limited number of cells to represent the solution space. If the water film is thin or the cloud map resolution is coarse, you might see a patchy or granular distribution instead of a smooth film.

3. Turbulent Fluctuations: If you're simulating a turbulent flow, the water film thickness may fluctuate due to the turbulent eddies. These fluctuations can be captured by the DPM and reflected as a granular distribution in the cloud map.

1. Model Convergence Issues: If the DPM-EWF model hasn't fully converged, the solution might be unstable and show inconsistencies like a granular film.

Here are some steps you can take to address these potential causes:

• Refine Particle Size Distribution: Try reducing the range of particle sizes in the DPM or increasing the number of size classes. This will provide a more accurate representation of the water droplet size distribution and potentially lead to a smoother film in the cloud map.
• Increase Cloud Map Resolution: If possible, increase the number of cells in your cloud map to capture the variations in film thickness more accurately. This will allow for a smoother representation of the film.
• Reduce Turbulence Intensity (if applicable): If the granular distribution is due to turbulent fluctuations, consider reducing the turbulence intensity in your simulation (if the physics allows it) to see if the film becomes smoother.
• Ensure Model Convergence: Double-check your convergence criteria and run the simulation for a longer time to ensure the solution has fully converged. An unconverged solution can lead to various inconsistencies in the results.

By investigating these factors and making adjustments to your model setup, you should be able to achieve a smoother representation of the water film thickness in your cloud map.