No abstract

To investigate the suitability of computational fluid dynamics (CFD) with regard to windbreak aerodynamics, simulations are performed with a state-of-the-art numerical scheme (Fluent) and compared against experimental data for two-and three-dimensional disturbances, namely the case of a long straight porous shelter fence and the case of a shelter fence erected in a square about an enclosed plot. A thorough sensitivity study quantifies the impact of numerical choices on the simulation (e.g. grid-point density, domain size, turbulence closure), and leads to guidelines that should ensure objective simulation of windbreak flows. On a fine grid Fluent's "realizable k-closure" gives results that are in qualitative accord with the observed mean winds.

This paper investigates a novel method for the control of 'morphing' aircraft. The concept consists of a pair of articulated split wingtips, independently actuated and mounted on a baseline flying wing. The general philosophy behind the concept was that adequate control of a flying wing about its three axes could be obtained through local modifications of the dihedral angle at the wingtips, thus providing an alternative to conventional control effectors such as elevons and drag rudders. Preliminary computations with a vortex lattice model and subsequent wind tunnel tests demonstrate the viability of the concept, with individual and/or combined wingtip deflections producing multi-axis, coupled control moments.

† The observed kink in the moment coefficient curves, when the fore wing-tip passes in the rear wing-tip plane, is predicted by the VLM as well but not to the same extent, especially when the wing angle of attack is small, see Figs (a) vs (b). This might suggest that modelling the wake interference from the leading wing-tip on the trailing wing-tip would be particularly important when both of them are in close alignment. This modelling could be enhanced by replacing the rigid wake model by a force-free wake model within the VLM. However, the RANS method, which intrinsically accounts for the wake roll-up (force-free wake), does not enable improved predictions in the kink region of the moment curves (Figs 8(e) and 9(e)), except maybe in terms of rolling moment - Fig. 7(e). †

No abstract