Rajiv Shenoy

Unstructured Overset Mesh Adaptation with Turbulence Modeling for Unsteady Aerodynamic Interactions

Schemes for anisotropic grid adaptation for dynamic overset simulations are presented. These approaches permit adaptation over a periodic time window in a dynamic flowfield so that an accurate evolution of the unsteady wake may be obtained, as demonstrated on an unstructured flow solver. Unlike prior adaptive schemes, this approach permits grid adaptation to occur seamlessly across any number of grids that are overset, excluding only the boundary layer to avoid surface manipulations. A demonstration on a rotor/fuselage-interaction configuration includes correlations with time-averaged and instantaneous fuselage pressures, and wake trajectories. Additionally, the effects of modeling the flow as inviscid and turbulent are reported. The ability of the methodology to improve these predictions is confirmed, including a vortex/fuselage-impingement phenomenon that has before now not been captured by computational simulations. The adapted solutions exhibit dependency based on the choice of the feature to form the...

Exploration of the Physics of Hub Drag

Main rotor hubs contribute signi cantly to the helicopter’s parasite drag. Due to the complex geometry of typical hub con gurations, large uncertainties in loads and wake ow eld phenomena inhibit the development of improved concepts at the design stage. Experimental and computational evaluations of the near wake of a generic, subscale complex rotor hub are explored. Prior e orts have shown that state of the art computational uid dynamics (CFD) simulations are accurate enough to predict drag characteristics of the complex hub. Velocity pro les and turbulence spectra measurements in the hub near wake (0.5 1.0 hub diameters) correlate well with CFD when proper delity of grid, time step, and turbulence model are chosen. The wake spectral content is characterized by broadband turbulence in addition to large scale spectral content energizing the ow eld. Current results substantiate earlier ndings of the role played by Magnus e ect due to bodies of rotation in forward ight.