Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Improved aerodynamic analysis tool

For several reasons the aerodynamic analysis of ram-air parachute systems is a very intricate and crucial task. The flexible textile wing structure interacts with the pressure distribution resulting from the surrounding external and internal flow field and vice versa. Unsteady processes ranging from canopy deployment, spreading, and filling process to dynamic flight manoeuvres like landing flare or rapid turn initiation are out of reach for nowadays-standard aerodynamic analysis tools. Special features of the parafoil-payload system -e.g. the complex arrangement of large numbers of suspension lines and the close coupling between flight mechanics, (local) free stream velocity resulting from the actual flight path, and changing geometrical shape of the canopy - do not ease the process of aerodynamic analysis.

Therefore most of the theoretical methods available focus on description of the aerodynamic behaviour of fully inflated ram-air canopies in steady flight conditions. Only a few computer codes offer the capability to perform an iterative coupling between a solver for the flow and a deformation analysis of the textile wing structure. Unfortunately most of these programs concentrate on one aspect of the coupling, i.e. either a highly accurate flow simulation is coupled with an elementary method for the structural analysis or very simple aerodynamic modelling is combined with highly detailed finite-element methods for the treatment of the textile structure.

In the frame of FASTWing an advanced simulation tool will be developed at CFD Norway combining both, an up-to-date flow simulation with an adequate representation of the structural part. Of course, such complex tool cannot be used for all kind of analysis needed during the design process as the corresponding effort w.r.t. man power and computational resources is tremendous. Therefore also an improvement of established methods is followed up. Handbook design procedures as well as singularity (panel) methods at several levels of complexity are applied and, whenever possible, improvements are added. At the same time reduction of empirical corrections to be applied with these type of methods is the major concern, as an increasing independence on empirical data coming from existing (and therefore old) design solutions is the only way to open up the field for innovative design alternatives.

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EADS Space Transportation
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