IKA-FLOW : A Flexible Body Overset Mesh Implementation for Fish Swimming





CFD, fish swimming, overset swimming, fish simulation


Simulation of inertial aquatic swimmers requires fluid structure interactions with temporal body geometry deformation. In practice,  his results in a change of the computational domain boundaries that represent the ”swimmer.” These simulations are traditionally done  sing body-fitted mesh and mesh morphing methods, but have drawbacks of negative cell volumes and small time-steps to  account for the complex swimming motion. In contrast, the overset mesh method, also provided by OpenFOAM®, overcomes most of  the drawbacks of the mesh morphing method at the expense of interpolation error. The current OpenFOAM® overset motion library only supports rigid body motion and cannot be used to resolve a body undergoing undulation. A modified motion solver is presented that allows for the complex mesh motion of an overset mesh for four body-caudal fin (BCF) virtual swimmers. The results of this solver are compared with published data of body-fitted meshes. The effect of different simulation parameters (including number of solving iterations, time delay, and temporal resolution) is investigated. Additionally, a novel simulation and comparison of the Ostraciiform locomotion mode with Anguilliform, Carangiform, and Thunniform modes are made investigating the wake, drag and lift. It is concluded that fish undulation has a marked effect on reducing lift generation. Lastly, a comparison of turbulence models (Spalart-Allmaras, k − ω SST, and k − kL − ω) at multiple Reynolds numbers shows that all three models have similar performance at lower Reynolds numbers but diverge at higher numbers.

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How to Cite

Coe, M., & Gutschmidt, S. (2023). IKA-FLOW : A Flexible Body Overset Mesh Implementation for Fish Swimming. OpenFOAM® Journal, 3, 75–119. https://doi.org/10.51560/ofj.v3.89



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