Nonprofit organization bringing together a global team to develop innovative solutions for wildlife conservation.
The Eagle Ray aircraft is a blended-wing body UAS designed to fly over the Himalayan Mountain Range at 20,000 feet. The goal is to monitor endangered snow leopard populations, offering protective solutions to poaching, habitat destruction, and dwindling populations.
My objective was to characterize the baseline aerodynamic performance of Eagle Ray across a range of angles of attack. I compared lift, drag, pitching moment, and lift-to-drag ratio using methods with different modeling assumptions and computational requirements.
To keep the workflow accessible to KWF’s nonprofit team, I prioritized open-source tools and evaluated what could be achieved on a standard laptop. I supplemented the local analysis with cloud-based simulations to investigate differences between the approaches.
Established a computationally inexpensive baseline using the vortex lattice method to evaluate aerodynamic trends.
Used steady-state RANS simulations to include viscous effects and compare results against the VLM baseline.
Used cloud computing to run a more refined mesh and compare the predicted aerodynamic coefficients with the local simulations.
I modeled cruise conditions at 20,000 ft with a freestream velocity of 26.04 m/s and a chord-based Reynolds number of approximately 1.03 million. Both CFD configurations used steady-state, incompressible RANS with the k–ω SST turbulence model.
To reduce computational cost, I modeled half of the aircraft with a symmetry boundary condition along the x-z plane. Cartesian refinement regions concentrated cells around the aircraft and wake; the OpenFOAM mesh was limited to ~3.5 million cells, while SimScale enabled up to 80 million cells.
I examined surface y+ to assess near-wall resolution. The figures below highlight the more consistent distribution achieved in SimScale. Because the meshes and domain sizes differed, this comparison was not a controlled mesh-convergence study.
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AoA [deg]The aerodynamic coefficients are in reasonable agreement between OpenFOAM and SimScale. The stall onset shown by SimScale around 15° AoA is not completely captured by OpenFOAM, showing where the model experiences limitations.
As expected, the VLM model underpredicts drag because of the attached and inviscid flow assumptions. The pressure distribution along the blended-wing body is highly dependent on flow separation, which is not captured by the VLM model.
Cross-referencing two independent CFD solvers was an incredibly valuable part of this process, as it allowed for the identification of discrepancies and built confidence in the results. Overall, this analysis provided a solid aerodynamic foundation for the Eagle Ray, yielding reliable coefficient data across a full range of angles of attack.