Fluid-structure interaction of the Jaguar XK8 convertible car roof

Abstract

The designer of convertible vehicles needs to consider the acoustical properties, quality of the interior environment, fatigue life and the aesthetic integrity of the flexible roof. Each of these concerns is affected, to a greater or lesser extent, by the interaction of the flexible roof material and its supporting structure with the aerodynamic loading on the material. For many convertibles, the roof quickly settles into a deformed shape for which the roof's internal forces are in equilibrium with the aerodynamic loading. The use of mathematical modelling can reduce the amount of time spent using experimental methods to assess a large number of design alternatives. A better understanding of the problem is obtained in the computational approach due to the increased amount of information which is gathered as part of the calculation. Also, the approach can be used at the concept stage of a product as the lengthy and costly build of a physical model is not required until later in the design cycle. The current research investigates the flow-induced deformation of the Jaguar XK8 convertible roof using a numerical method. A computational methodology is developed that entails the coupling of a commercial Computational Fluid Dynamics (CFD) code with a third-party structural solver. The computed flow-structure interaction yields stable solutions, the aerodynamically loaded flexible roof settling into static equilibrium. The flow-structure interaction is found to yield a static deformation to within 1% difference in the displacement variable after three iterations between the fluid and structural codes. The methodology is also shown to be robust even under conditions beyond those likely to be encountered. The full methodology could be used as a design tool. However, the present work demonstrates that reasonably accurate predictions, to within 20%, are possible using only a single iteration between the fluid and the structural codes.