CFD Modeling of a Wingsuit

Abstract

An experienced wingsuit pilot may be able to cover a horizontal distance up to three meters for each meter of vertical fall in steady flight. Such a glide ratio of 3:1 is dramatically much better than can be achieved by ordinary parachutists or BASE- (Buildings, Antennae, Spans and Earth) jumpers. Use of wingsuits makes BASE-jumping a potentially much safer exercise and parachute jumping even more entertaining. A major focus for wingsuit design is to achieve a maximal glide ratio while maintaining sufficient maneuverability. Inspired by a new type of wingsuit design of Norwegian origin, the Wingrig, the 3D mechanical design software Autodesk Inventor was used to construct a simplified representation of a 3D wingsuit. The simulation domain and the grid for this domain were generated by use of software packages in the Ansys Workbench v13.0 environment. All simulations were run by Ansys FLUENT v12.0, applying the realizable k-epsilon turbulence model with standard wall functions.Predictions of the model were tested in a wind tunnel experiment at the Norwegian University of Science and Technology (NTNU), making use of the Wingrig. Despite the lack of experimental data for high angles of attack, the predicted lift coefficient was in reasonable agreement with the experimental results. There was, however, a non-negligible quantitative difference between the predicted and observed glide ratio curves, reflecting that the model underestimates drag. A major explanation for this underestimation is that the applied turbulence model does not resolve the viscous boundary layer. In addition, the smooth nature of the computational wingsuit model lowers the drag. As the main aerodynamic properties of the wingsuit were captured by the model, the design was given a lower armwing and a lower armwing attachment point to study the effect of a more blocked legwing leading edge. The revised model showed a reduction in glide ratio of about 8% due to an increase of the drag coefficient. The drag increase was partly due to the generation of a stronger vortex at the wingtip and thus higher induced drag in this region. In addition, the blockage caused by the armwing attachment point on the leg wing of the revised model, is also shown to have an effect on the drag. Since the glide ratio is the most important parameter in wingsuit design, the results suggest that a free leg wing characterizing the Wingrig is a design feature that should be exploited further.