Inviscid flow calculation around a flexible airship

In the context of an airship development programme, inviscid flow behavior and its coupling with structure flexibility are investigated. For this purpose, we have chosen a nonlinear analysis tool relying on the unsteady Euler model for the flow part and the classical elastodynamic equations for the structure. The numerical model for the flow is based on a Mixed Element Volume discretization derived in an Arbitrary-Lagrangian- Eulerian framework in order to cope with the structural deformations. The case of low- Mach flows (natural flight regime for an airship) can be handled by a special dissipation preconditioner which improves the accuracy of the flow simulation. The structural model, coupled to the flow solver, is discretized by the finite element method in a Lagrangian formulation. In this work we have performed a series of inviscid flow calculations with the goal to evaluate accurately the global aerodynamical coefficients. We first compare the influence of different stiffeners in the airship structural model for flows with zero and nonzero (20?) angle of attack. Then, we study the influence of the numerical dissipation and of the low-Mach preconditioning. We observe -as expected- the stabilizing effect of the stiffeners, specially longitudinal ones. The positive impact of low Mach preconditioning and numerical dissipation on the results is also evaluated.

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