Komerath, N., Hiremath, N., Shukla, D., Robinson, J. et al., "Aerodynamic Loads on Arbitrary Configurations: Measurements, Computations and Geometric Modeling," SAE Technical Paper 2017-01-2162, 2017.
This paper brings together three special aspects of bluff-body aeromechanics. Experiments using our Continuous Rotation method have developed a knowledge base on the 6-degree-of-freedom aerodynamic loads on over 50 different configurations including parametric variations of canonical shapes, and several practical shapes of interest. Models are mounted on a rod attached to a stepper motor placed on a 6-DOF load cell in a low speed wind tunnel. The aerodynamic loads are ensemble-averaged as phase-resolved azimuthal variations. The load component variations are obtained as discrete Fourier series for each load component versus azimuth about each of 3 primary axes. This capability has enabled aeromechanical simulation of the dynamics of roadable vehicles slung below rotorcraft. In this paper, we explore the genesis of the loads on a CONEX model, as well as models of a short and long container, using the “ROTCFD” family of unstructured Navier-Stokes solvers. The paper also describes the problem of generating computational geometries of models that start as wind tunnel models, not as computer-generated numerical shapes. Photogrammetric reconstruction has been refined, to enable measuring the geometry of models even where the surface is shiny or complex, such as the sides and the underside of road vehicle models. A simple laws-of-physics verification of the volume is obtained using the buoyancy occurring when immersing the model in water. These measurements are used to obtain a numerical solid model, that is then used in generating computational grids for models of roadable vehicles such as a HumVee and a Tactical Response Vehicle. Results show encouraging success in obtaining correct azimuth-resolved aerodynamic loads on the generic shapes, with computational demands being moderate enough to permit 5-degree resolved results.