2D BFS flow CFD

asda3D · April 22, 2018, 05:20

Hi there am trying to create a uniform mesh for a 2d turbulent step flow problem. I would like to accurately record the data for recirculation region after the step. To improve the mesh quality I decided to split the 2d step into faces and meshed each of them by manipulating edge sizing. However, when I use edge sizing to refine the mesh, I am unable to use inflation layers at the walls. This lead to an inaccurate simulation in fluent. Any ideas on how I could go about to get a very fine uniform mesh will wall inflations. Much appreciated as always

flotus1 · April 22, 2018, 07:57

I assume you are trying to do this in Ansys mesher?
There are in general three possible approaches:
A uniform quad mesh is definitely the best and should be feasible in 2D steady state.
The other two are outlined here:
bfs_mesh.png
Blue lines indicate splits, gray lines indicate cell boundaries. There are pros and cons to each method. The first one only has cells with 90° angles, but their aspect ratio even further away from the wall might become very high. The second one does better in this regard, but cells are skewed. The first method could be improved further by adding more splits to achieve a constant cell size further away from the wall.
Both methods are possible in Ansys mesher with splits or building the geometry from parts, but at some point learning a more advanced tool like ICEM would be worth it.

April 22, 2018, 05:20	2D BFS flow CFD	#1
asda3D New Member anonymous Join Date: Apr 2018 Posts: 26 Rep Power: 8	Hi there am trying to create a uniform mesh for a 2d turbulent step flow problem. I would like to accurately record the data for recirculation region after the step. To improve the mesh quality I decided to split the 2d step into faces and meshed each of them by manipulating edge sizing. However, when I use edge sizing to refine the mesh, I am unable to use inflation layers at the walls. This lead to an inaccurate simulation in fluent. Any ideas on how I could go about to get a very fine uniform mesh will wall inflations. Much appreciated as always

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April 22, 2018, 07:57		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	I assume you are trying to do this in Ansys mesher? There are in general three possible approaches: A uniform quad mesh is definitely the best and should be feasible in 2D steady state. The other two are outlined here: bfs_mesh.png Blue lines indicate splits, gray lines indicate cell boundaries. There are pros and cons to each method. The first one only has cells with 90° angles, but their aspect ratio even further away from the wall might become very high. The second one does better in this regard, but cells are skewed. The first method could be improved further by adding more splits to achieve a constant cell size further away from the wall. Both methods are possible in Ansys mesher with splits or building the geometry from parts, but at some point learning a more advanced tool like ICEM would be worth it.