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This paper deals with numerical simulations on a self-propelled fish-like body. Firstly, the methods used to achieve such simulations based on the solution of the Reynolds-Averaged-Navier-Stokes Equations are described: resolution of the Newton's law (parameterization, use of a description of the rotation based on a quaternion), regridding strategies linked to body motion and deformation, fluid-motion coupling methods. In the second part, realistic applications are shown. The interaction between the fluid and the body is fully solved since the evolution of the body's position is not imposed but computed. Only the imposed deformation of the shape and its interaction with the fluid produce forces on the body and, consequently, motion.

This paper presents an investigation of RANS and DES models for the Ahmed body with 25 • and 35 • slant angles. The Reynolds number, based on the height of the model and the upstream velocity, is 7.68×10 5 . Two RANS ( Reynolds Averaged Navier-Stokes) models are used: the k − ω SST of Menter and the EARSM (Explicit Algebraic Stress Model), based on the k − ω model. Two hybrid RANS-LES (Large Eddy Simulation) models are used: a DES (Detached Eddy Simulation) and an IDDES (Improved Delay Detached Eddy Simulation). These hybrid models are also based on the k − ω model. The flow for the slant angle 35 • is well predicted by all turbulence models with a slight advantage for the IDDES model. For the flow with the slant angle 25 • , only the IDDES hybrid RANS-LES model predicts the recirculation bubble on the slant. It is concluded that the IDDES model is the only turbulence model that gives good agreements with the experimental data.