Real time simulation of air-to-air refuellin

This thesis presents the development of numerical simulation of real-time air- to-air refuelling. The air wake model behind the tanker was prescribed as a three dimensional non-linear array of wake velocities, which was obtained by application of non-linear vortex roll-up computer codes. Estimation of interpolation errors at the grid cell centroid in the tanker wake are verified. Correlation of tanker wake velocities for different tanker lift coefficients is also presented. Compressibility effects are also included in the tanker wake. To model the receiver aircraft in a real-time simulation, a single point, multi-point and strip theory models are developed. The report also presents a flat wake panel model for large receiver aircraft e.g. VC10. The report presents a comparison between single point and multi-point results at varying receiver position in the tanker wake. The results from single point method are found to be adequate for small receiver aircraft e.g. Tornado and the flat wake panel model presents a good comparison between predicted and exact results for large receiver aircraft e.g. VC-10. The thesis presents the results from the interaction of the drogue and the receiver aircraft's nose. To predict the airflow around the nose of the receiver aircraft, an off the shelf axisymmetric surface ring vortex model is used. Calculations for the velocities induced by the receiver Tornado nose at small incidence are made using slender body theory and are found to be negligible. The hose has been independently modelled as a succession of finite elements for the case of real time air-to-air simulation. Real Time Simulation of Air-to-Air Refuelling The finite element model has been further developed to predict the hose and drogue static trail position under the influence of the tanker wake and receiver nose flowfield. Iterative techniques are developed to predict the forces induced at the probe of the receiver Tornado aircraft during post-contact; the results for which are presented as a set of mathematical relations for ease of integration into real-time simulation. To simulate the dynamics of the hose and drogue, a perturbation model has been developed. Both longitudinal and lateral cases have been analysed. The static results from the dynamic model are compared to the finite element model of the hose and drogue. The thesis includes the results for pre-contact drogue and receiver nose interaction, pre-contact hose and drogue dynamics and post contact forces induced on the receiver aircraft operating within the tanker wake. The models presented in this thesis have been successfully incorporated and validated by a test pilot for a Tornado refuelling from a VC10 into DERA, Bedford air-to-air simulation. Real Time Simulation of Air-to-Air Refuelling.