What is this mesh's topology?

Transonic · December 18, 2023, 13:11

Hi, I came across this video on youtube, and would like to know more about the mesh (for a cylinder) such as the internal structure? is there a reason to do it that way?

Am i correct in saying there is an o-grid around the cylinder?

Capturee.PNG

Source:https://www.bing.com/videos/rivervie...F&&FORM=VRDGAR

JBeilke · December 18, 2023, 15:39

It's an O-grid around the cylinder but with a horrible mesh quality. They should do some smoothing to get rid of the jumps in cell sizes.

Transonic · December 18, 2023, 16:41

Hello JBeilke. So an O grid around the cylinder, but for the rest of the area, what’s special about it please? Is there any name for having it structured that way?

Also, was the ‘wake’ kept longer for a particular reason?

LuckyTran · December 18, 2023, 19:22

O-grid is the name for this style of grid. It's so-called "O" because the topological lines around the cylinder form an O. Other topologies are the worser C-grid and even worser H-grid. An O-grid allows for the surface mesh around the cylinder to conform to the cylindrical surface and minimizes the grid skewness between the structured blocks. O-grids allow gradual/rapid grid stretching away from the cylinder in all directions. However, an O-grid needs a grid smoother to generate cells that stretch smoothly.

C-grids and H-grids don't need any smoother, because their topology isn't smoothable. They're simpler and very easy to setup. However, their best skewness even with a smoother is worse than an O-grid with a smoother.

The O tells you the arrangement of the blocks. Each of the blocks will be structured blocks and don't really get any special names.

The wake is longer because you want to simulate enough of the downstream mixing behind the wake so that it doesn't interact with the outlet BC and impact the results. Flow doesn't "flow" upstream, so you can have an inlet closer to the body.

Transonic · December 19, 2023, 05:23

Hi LuckyTran, that’s a really amazing reply! How did you learn about the topology like that? Did you learn it from a book or something please? I’d love to give it a read if it’s from a book or something

Just curious, but how could the flow flow upstream? Would this depend on the upstream velocity please?

Thanks!

December 18, 2023, 13:11	What is this mesh's topology?	#1
Transonic Member Join Date: Jan 2023 Posts: 32 Rep Power: 3	Hi, I came across this video on youtube, and would like to know more about the mesh (for a cylinder) such as the internal structure? is there a reason to do it that way? Am i correct in saying there is an o-grid around the cylinder? Capturee.PNG Source:https://www.bing.com/videos/rivervie...F&&FORM=VRDGAR

December 18, 2023, 15:39		#2
JBeilke Senior Member Joern Beilke Join Date: Mar 2009 Location: Dresden Posts: 516 Rep Power: 20	It's an O-grid around the cylinder but with a horrible mesh quality. They should do some smoothing to get rid of the jumps in cell sizes. Transonic likes this.

December 18, 2023, 19:22		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,747 Rep Power: 66	O-grid is the name for this style of grid. It's so-called "O" because the topological lines around the cylinder form an O. Other topologies are the worser C-grid and even worser H-grid. An O-grid allows for the surface mesh around the cylinder to conform to the cylindrical surface and minimizes the grid skewness between the structured blocks. O-grids allow gradual/rapid grid stretching away from the cylinder in all directions. However, an O-grid needs a grid smoother to generate cells that stretch smoothly. C-grids and H-grids don't need any smoother, because their topology isn't smoothable. They're simpler and very easy to setup. However, their best skewness even with a smoother is worse than an O-grid with a smoother. The O tells you the arrangement of the blocks. Each of the blocks will be structured blocks and don't really get any special names. The wake is longer because you want to simulate enough of the downstream mixing behind the wake so that it doesn't interact with the outlet BC and impact the results. Flow doesn't "flow" upstream, so you can have an inlet closer to the body. Transonic likes this.

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December 18, 2023, 16:41		#3
Transonic Member Join Date: Jan 2023 Posts: 32 Rep Power: 3	Hello JBeilke. So an O grid around the cylinder, but for the rest of the area, what’s special about it please? Is there any name for having it structured that way? Also, was the ‘wake’ kept longer for a particular reason?

December 19, 2023, 05:23		#5
Transonic Member Join Date: Jan 2023 Posts: 32 Rep Power: 3	Hi LuckyTran, that’s a really amazing reply! How did you learn about the topology like that? Did you learn it from a book or something please? I’d love to give it a read if it’s from a book or something Just curious, but how could the flow flow upstream? Would this depend on the upstream velocity please? Thanks!