E​RCOFTAC PC Italy

Supersonic Capsule Wake Interaction with a Disk-Gap-Band Parachute

Authors: Luca Placco
(Università degli Studi di Padova, Italy)

Thomas Hancock
(Vorticity Ltd, United Kingdom)

Francesco Picano
(Università degli Studi di Padova, Italy)

Contours of numerical Schlieren (density gradients) highlighting shock structures and highly turbulent flow around the capsule and parachute; axial plane cross section. The parachute frontal bow shock is observed to oscillate due to interaction with the turbulent flow originating from the capsule.

Scientific Abstract

The visualisation is based on a set of high-fidelity, time-resolved simulations of a rigid disk-gap-band (DGB) parachute trailing a descent module in a supersonic regime. The study employs Large-Eddy Simulation combined with an Immersed Boundary Method and GPU parallelisation to reproduce the Rosalind Franklin ExoMars flight geometry at Mach 2 in a rarefied Martian atmosphere. The parachute is modelled as a rigid surface in order to isolate fluid-dynamic effects and minimise modelling assumptions. We analyse the “breathing” instability phenomenon, which is associated with oscillations of the parachute frontal bow shock driven by its interaction with turbulent flow originating from the upstream forebody. The flow field surrounding the DGB and its unsteady statistics are examined to identify mechanisms that promote flow stabilisation compared with other parachute design shapes. Results show that the DGB exhibits significantly lower axial and tangential force fluctuations than non-slotted counterparts. This behaviour originates from a persistent annular outflow through the gap, which confines the main toroidal vortex within the canopy cavity. By limiting backflow, the gap reduces turbulence–shock interaction ahead of the parachute. As a result, the frontal bow shock remains closer to the canopy and appears flatter. The amplitude of stand-off distance oscillations is also reduced, while high-frequency components associated with lateral bow-shock modes are strongly damped due to more effective off-axis stabilisation. Overall, the simulations indicate that the DGB geometry mitigates the intensity of the “breathing” instability by altering the extent of wake–shock interaction through its annular gap outflow.

Relevant publications:

L. Placco, G. Soldati, M. Bernardini, F. Picano, "On flight instabilities of capsule-rigid parachute system during supersonic planetary descent", Aerospace Science and Technology 160, 110026, 2025

L. Placco, M. Cogo, M. Bernardini, A. Aboudan, F. Ferri, F. Picano, " Large-Eddy Simulation of the unsteady supersonic flow around a Mars entry capsule at different angles of attack " Aerospace Science and Technology 143, 108709, 2023

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