The present study concerns the investigation of external natural convection driven around a Montgolfiere scientific balloon. Ground measurements are carried out on a small scale heated model located within an enclosure. Non intrusive planar Particle Image Velocimetry and thermocouple sensors are used to characterize both dynamical behavior of the flow generated around the balloon and heat transfers on its surface. It is shown that a relative good agreement is reached on wall heat transfers with simplified axisymmetrical 2D RANS simulations. However significant discrepancies exist regarding the analysis of the flow topology and dynamic quantities in comparison with the experimental data. The proposed numerical rebuilding is thus completed with a 3D Delayed Detached Eddy Simulation (DDES) in order to overcome conventional RANS approach inability to represent low frequency thermal plume instabilities.

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