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I want to take a look at the default settings. Initially you've got this happy fun time slider bar. I call it the happy fun time slider bar because it doesn't tell you anything. How accurate do you want it to be? 3! Yay! How about 4? Awesome! Now what is 3 versus 4? It's actually quite a lot of things. So I will show you what that is and how that works.
But here's that close thin slots option. That is the another quick way to close leaks in a sheet metal enclosure.
For level of initial mesh, the default value is 3. I'm going to jump into the manual mode. In manual mode, it starts wherever you left off. So if you picked five and then jump into manual mode, that's going to be the starting point. It gives you a basic mesh, looks about like this, tries to keep the squares as close to an aspect ratio of one as possible.
The typical default values are level of two refinement on narrow channels with a characteristic number of cells of 5, advanced refinement of four, and geometric tolerance level of five. That's usually the default values, although usually it'll update as you start using it. It might switch over to a different, default starting value. These values can be problematic, let me talk about what exactly meshing is doing and why it can be problematic.
When you do a mesh, you start out with a basic mesh. Each element in that basic mesh is one element, one data point. And if you refine that to level 2, you split that in 3 directions. So 2 to the 3rd power is 8. Now if you were to split all of those again, You would hit 64. Now that's only two refinement levels up. We're now 64 times bigger, and every time you go up another refinement level, your mesh count starts to explode exponentially. This is what can create massive meshes. This is one of the reasons you want to simplify your geometry, but you don't have to do geometry simplification to achieve an efficient mesh. And here's the key, we need an efficient mesh. We're not ready for a final solve. This study is not set up and ready to give us that solve that takes all afternoon or all night and gives us a super accurate result.
We don't have confidence in this study setup yet. So we need a very efficient mesh to start with. Then go back and do things like unsuppress all the components on the circuit board. and run it all night and do all that kind of fun stuff. This is what the meshing dialog looks like and I'm going to try to explain meshing and mesh controls in Flow Simulation as a balance between what you want and what you have to offer.
For example, narrow channels. That's the very first mesh refinement characteristic that you can set. Five is the characteristic number of cells across a channel. Those slots on the sides of the enclosure where I'm going to put my pressure boundaries, those are channels, right? Two opposing faces separated by a gap. So what I'm telling it is I want five elements to, cover that gap opening. You're gonna have to refine from your basic mesh a certain number of times to hit that number. How many times do you have to refine? I don't know. But what I've done here is I've said two is the refinement level that I am willing to give. I have two refinement levels to give to the channel refinement strategy. So if you see a channel, and it has less than 5 elements across the channel, refine it up to level 2, but no further.
This doesn't mean the mesh can't go beyond level 2, I just can't from a channel definition. And so what really gets complicated is elements are going to get meshed based on multiple overlapping criteria.
Let's go down to advanced refinement. It starts out with small solid feature refinement at level four. That's significantly smaller elements, at the larger refinement level than it is on the channels. In this specific study, you could turn off channel refinement and it would probably have zero impact on your results.
But refinement level four means if I see a sharp corner, I want refined mesh around that sharp corner. The last one that's enabled is down here, this tolerance level is five. If I have a bumpy surface, Even just a really small divot, like an embossed text that's just a thousandth of an inch thick.
I can go up to a level of five to refine that and get a good mesh around that text. Do I care about refined text? No, I absolutely do not care about embossed text. So like this reset button, around these screws and stuff like that, I'm expecting a really tight mesh in those areas.
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