Hi Jianguo, I can try to help with your first two questions.
1) As mentioned by Junting the first thing to do when generating the 3D airfoil mesh is to start by generating a nice 2D mesh. You then extrude in the spanwise direction. For the initial 2D mesh you can build some structured mesh faces in the boundary layer using the "transfinite line", "transfinite surface", and "recombine" options in gmsh. Then, in the unstructured farfield you can use the "Box" mesh refinement option, which lets you specify the element size inside the box and outside the box. Also, make sure to use at least the "set order 2" option in gmsh once the mesh is built, which will use quadratic curves to represent the surface. 2) In the paper, the y+ that is reported is that of the first solution point off the wall when using Gauss points. Since you have the mesh and therefore element sizes, and the Gauss point locations which can be looked up, you should be able to compute the x+ and z+ values from that information. On Tuesday, 3 September 2019 11:18:30 UTC-4, Junting Chen wrote: > > Let me put my two cents into the topic of GMSH regarding the questing 1. > I'm a user, too. > > Seems to me the process of creating such mesh in GMSH uses boundary layer > refinement field and box refinement field. The boundary layer refinement > field is only available in a 2d case, so you will have to create a 2D plane > and "extrude" it to a 3d domain. It's also the only way of generating > conformal mesh on the two surfaces which you are going to apply periodic > condition on. To create your 2D plane, you might have to get the > coordinates of the airfoil surface nodes first. > > I hope it helps. gmsh script can be lengthy... > > Junting > > On Tuesday, September 3, 2019 at 10:52:50 AM UTC-4, JG wrote: >> >> Dear PyFR developers and users, >> >> I have successfully reproduced the LES simulation of the flow around a >> sd7003 airfoil presented in the paper (On the utility of GPU accelerated >> high-order methods for unsteady flow simulations: A comparison with >> industry-standard tools, 2017 JCP). The results are quite good. >> >> Now, I want to perform LES of flow around a NACA0015 airfoil with angle >> of attack near stall angle and Reynolds number of around 60,000. The first >> difficulty encountered is the mesh generation. I have the following >> problems: >> >> 1. In the PyFR user guide, the free software Gmsh is used to generate >> mesh. As seen in the above JCP paper by the developers, the mesh used in >> LES of flow past airfoil is complex. The mesh is refined near the airfoil >> and in the rectangular wake region, and then quickly coarsened outside >> these regions. So, is there any example script that can be read into Gmsh >> to generate such a complex mesh for a LES simulation or any guide for >> complex mesh generation? >> >> 2. For a LES simulation, the grid resolution (dx, dy, dz) in streamwise, >> wall-normal and spanwise direction respectively must satisfy certain >> criterion. According to the above JCP paper, y+ in the first layer of mesh >> near wall is around 0.4. So, what is the grid spacing in streamwise (dx) >> and spanwise (dz) direction if the Reynolds number is around say 60,000? >> >> 3. Pointwise17.3R4 can generate mesh for PyFR. However, its seems that in >> Pointwise, one cannot specify periodic boundary conditions and there is no >> option for periodic BC. So, how can we impose the periodic BC when >> pointwise is used. >> >> It will be greatly appreciated if anyone can help answer the above >> questions or give some suggestion. >> >> Best regards, >> >> Jianguo >> >> -- You received this message because you are subscribed to the Google Groups "PyFR Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to pyfrmailinglist+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/pyfrmailinglist/9e5a1ed5-f3d9-427b-a9d1-be1734417686%40googlegroups.com.
