Saithe Fish Simulation: ANSYS Fluent Dynamic Mesh Setup

     One of the most famous post on the blog can be read here. Worryingly😁, many fellow researchers and readers are interested in the aerodynamics of flexible robots 🤓. In this post, the dynamic mesh 🕸 settings used are shared 🥰. These settings are used to reproduce 🖨️ the results from [1], all those years ago. All in a hope that this post helps the readers in their scholarly work! 🎩

     Once the UDF 💻 has been acquired, the next step is to apply the UDF to the airfoil 🐠 geometry correctly ✔️. The airfoil geometry at the first time-step 🕰 i.e. at t = 0 for UDF 02 obtained from [1] is made available here. Once on the dynamic 🏎️ mesh page, select the options shown in Fig. 1. The options selected in Fig. 1 show the default parameters. Within Fig. 1, "wing" refers to the named selection that includes the only the airfoil geometry. Named selections can be created during the meshing process. The "wing" named selection is shown in Fig. 3.

Fig. 1, The dynamic mesh settings

     Before following the settings in Fig. 1, do remember to compile the UDF. To compile the UDF, please use the settings shown in Fig. 2. After selecting the UDF, select the options as shown in the Fig. 2 and then select Build and Load.

Fig. 2, Compile UDF

Fig. 3, Named selection for the dynamic mesh

     The maximum Lift ⬆️ force coefficient from the simulations performed using the method explained here is at 1.77 as compared to 1.68 [1]. The average Drag ⬅️ coefficient is at 0.097 as compared to 0.103 [1]. The obtained flow-field 🏟️ is shown in Fig. 4. Within Fig. 4, top row has v and u components of velocity while the bottom row shows pressure field❗

Fig. 4, The flow-field

     If you are still having trouble, switch to immersed boundary method. The immersed boundary method code your truly wrote, is available here. The validation of this code is available here, here, here and more generally here.

     If you want to hire me as your next shining post-doc or collaborate in research, please reach out! Thank you for reading!

References

[1] Shi, Fulong, Xin, Jianjian and Ou, Chuanzhong, Li, Zhiwei, Chang, Xing, Wan, Ling, "Effects of the Reynolds number and attack angle on wake dynamics of fish swimming in oblique flows", Physics of Fluids, 37(2), 025205, 2025 https://doi.org/10.1063/5.0252506