Hello, i'm working on a store separation project and I don't know how to use dynamic meshing or overset mesh in Ansys Fluent. Can you give me some instructions about this topic? Thank you very much.

@hienaominh6588 Hi. Thanks for the message. I hope I can be of some assistance. When I use the tern dynamic meshing I'm referring specifically to the so called spring analogy method. This method works best when using tet elements. Don't bother if you are using poly or hex elements because it is quite a challenge to maintain acceptable mesh quality as the store moves away from the aircraft. Smoothing and reemeshing parameters must be fine tuned iteratively and that is a very time consuming process. So the way to go is to use overset meshing. This is such amazing technology that has been implemented in CFD codes. This is the so called "Chimera" method of meshing. To successfully release the store you need to take specific care to minimize or mitigate orphan cells. Secondly, you need to compile your UDF. I will discuss these in more detail now: 1. Orphan Cells: These are a result of insufficient overlap between background and component mesh. The idea here is to ensure that where the meshes overlap, cell sizes in each mesh are about the same size. The critical areas that are prone to orphan cells are the gaps between suspension equipment and store. In other words, where walls of overlapping meshes are close to each other. A trick to keep cell sizing similar or compatible in these regions is to use BOIs in the small gaps in both the background and component meshes. You also want to switch the donor priority method to cell based (accessed via the following TUI command: define\overset-interfaces\options\donor-priority-method 1) 2. UDF: You need to write .c file containing store mass, inertia and ejection profiles if present and data is available. Please look at Fluent documentation and tutorials (stores release which I believe can be found on Ansys Learning Hub) for sample UDF .c files. The trick that gets people undone is with compiling the UDF. To do this successfully you MUST ensure that you have the correct version of Visual Studio installed for your release of Ansys Fluent. Please search this online. I will report back later with more information on what to look for online. Once that is taken care of you can successfully compile the UDF. After that you need to hook the UDF to the store and the store domain (passive). The rest of the case setup will be exactly as you would do for any other external aero problem. Set turbulence model, boundary conditions, reference values, report files etc etc. You must first run a steady state simulation to provide the transient stage with an initial converged starting point. When switching to transient remember to enable gravity and set its value with correct sign and magnitude. When it comes to time step size I typically use 0.001 with 1200 steps for 1.2s worth of flow time. You can certainly experiment with coarser time steps but be careful not to go too coarse.

​@@azharcassim2795Hi. Thank you so much for your helpful response. I really appreciate your explanation and I understand the process now. However, I would still like to learn more about the meshing methods and how to use 6DOF. Would it be possible to contact you via email for further assistance? I would be very grateful for your help. Thank you again for your time and consideration.

Hello Karan, Could you do that?