If you haven't yet read, Meshing in Flow Simulation and Part 2, I would recommend doing so before reading this. I'm building off the basic mesh discussed in Part 2. In this post, I'm going to talk about the initial mesh.
The initial mesh of a Flow Simulation is the first mesh that is used for performing actual calculations. The software starts with the basic mesh, then refines area with certain geometrical features based on the different settings in the software. This post will be a discussion of those settings.
Before we discuss the actual settings here, let's talk about what all the level settings are since we see it multiple times in Small solid features refinement level, Curvature refinement level, and Tolerance refinement level.
The refinement level is the maximum amount of times a cube that represents a cell can be split. Each cube splitting into 8 equal cubes represents one level. The image below shows multiple refinement levels. If all the cells combine to make 1 starting cell, then the following is a table to put the different refinement levels in the image in perspective:
- Level 1: Red
- Level 2: Blue
- Level 3: Green
- Level 4: Yellow
- Level 5: Black
- Level 6: White
- Level 7 and Level 8: Uncolored because they are too small too make out. See second image for zoomed in view
You can imagine how many cells would be created if every cell was refined 8 times. The actual amount would be 8^8 or 16,777,216. That means that a single cell that would normally take about 10 kB of RAM to store would now produce about 16GB of RAM needed if all cells created by refinements were continually refined up to the max as well. And that's just from 1 cell out of the basic mesh! There can be thousands or millions in the basic mesh! This is why the settings exist. So that the software can sort out what needs refinement and what doesn't - otherwise you would never finish an analysis in any reasonable time frame.