# NACA0012：Oscillation on the wall **URL:** \ **Category:** General\ **Created:** [13 March 2022 14:46 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570 "2022-03-13T14:46:18Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![jian](https://avatars.discourse-cdn.com/v4/letter/j/7ba0ec/32.png) [@jian](https://pyfr.discourse.group/u/jian)\ **Post date:** [15 March 2022 15:46 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/22 "2022-03-15T15:46:05Z")
I take a look in Gmsh as Nunn said. I want to use your code to check grid，but it comes error，under the condition that h5py is installed. I use “python read.py” to launch the code. ---
**Author:** ![WillT](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@WillT](https://pyfr.discourse.group/u/WillT)\ **Post date:** [15 March 2022 15:49 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/23 "2022-03-15T15:49:16Z")
Ok, I’m just a bit confused as the screenshot from @nnunn seems to show that although gmsh is using high order elements, the surface is faceted i.e. not high order. ---
**Author:** ![nnunn](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@nnunn](https://pyfr.discourse.group/u/nnunn)\ **Post date:** [15 March 2022 23:48 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/24 "2022-03-15T23:48:33Z")
Hi @jian - in PyFR, a **high-order** mesh implies that the mesh has **curved** elements. In your case, the triangles are all **linear** , i.e. all the edges are **straight**. Your mesh is using 10-node triangles (high-order) to define triangles with straight edges. Usually, gmsh uses those 10-node triangles to define triangles with curved faces. So, to simulate a curved (high-order) aerofoil, we need to generate the gmsh .msh file using curved geometry (e.g. splines). How did you generate your mesh? If you used gmsh, can you send the .geo “geometry” file? ---
**Author:** ![jian](https://avatars.discourse-cdn.com/v4/letter/j/7ba0ec/32.png) [@jian](https://pyfr.discourse.group/u/jian)\ **Post date:** [16 March 2022 00:15 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/25 "2022-03-16T00:15:11Z")
Thanks a lot. This is my .geo file. > **[NACAc.geo](https://drive.google.com/file/d/1sfQ0x7nSFjOgmBmqPuI2I1xc7kw0UyYc/view?usp=sharing)** > > Google Drive file. ---
**Author:** ![nnunn](https://avatars.discourse-cdn.com/v4/letter/n/c89c15/32.png) [@nnunn](https://pyfr.discourse.group/u/nnunn)\ **Post date:** [16 March 2022 09:31 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/26 "2022-03-16T09:31:29Z")
Hi @jian - using splines instead of lines through your points we get excellent curved geometry for gmsh to mesh. In [this google folder](https://drive.google.com/drive/folders/1kIQDMxPSS6AX756qFSaHwhopF5EiA5mT?usp=sharing) you’ll find “ **NACA\_p3\_5751.msh** ”, a mesh with 5751 3rd order triangles, plus “ **NACA\_curved.geo** ”, the geometry file used to generate the mesh. If you want to reproduce and improve this mesh, I used these settings (with gmsh v4.9): From the [Options] panel on the [Mesh/General] tab, I set: - 2D algorithm to [MeshAdapt] - Element order to [3] - Max element size [2] Note that gmsh has lots of way to constrain the size of mesh elements. As a first step, I fiddled with “characteristic sizes” for the points to produce a mesh of size similar to yours. Better alternatives are to use background fields, boundary layers, nested transfinite regions, etc. See the gmsh documentation for inspiration. Also in [that folder](https://drive.google.com/drive/folders/1kIQDMxPSS6AX756qFSaHwhopF5EiA5mT?usp=sharing) are some pictures of the mesh, plus snapshots from various runs, each at time = 20: ```auto [slip_wall_N4_t20.jpg]: Navier-Stokes / order 4 / mu 1e-6 / slip wall BC [no_slip_wall_N4_t20.jpg]: Navier-Stokes / order 4 / mu 1e-6 / no-slip wall BC [no_slip_wall_N4_t20_mu0.jpg]: Navier-Stokes / order 4 / mu 0 / no-slip wall BC ``` Good luck! ---
**Author:** ![jian](https://avatars.discourse-cdn.com/v4/letter/j/7ba0ec/32.png) [@jian](https://pyfr.discourse.group/u/jian)\ **Post date:** [17 March 2022 00:27 UTC](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570/27 "2022-03-17T00:27:35Z")
Okey, thanks a lot. Again, thanks for your kindness replay and best regards. [Previous page](https://pyfr.discourse.group/t/naca0012-oscillation-on-the-wall/570.md?page=1)