View Video Presentation: https://doi.org/10.2514/6.2022-3218.vid
The ability to accurately and rapidly assess unsteady interactional aerodynamics is a shortcoming and bottleneck in the design of various next-generation aerospace systems: from electric vertical takeoff and landing (eVTOL) aircraft to airborne wind energy (AWE) and wind farms. In this study, we present a meshless CFD framework based on the reformulated vortex particle method (rVPM) for the analysis of complex interactional aerodynamics. The rVPM is a large eddy simulation (LES) solving the Navier-Stokes equations in their vorticity form. It uses a meshless Lagrangian scheme, which not only avoids the hurdles of mesh generation, but it also conserves the vortical structure of wakes over long distances with minimal numerical dissipation, while being 100x faster than conventional mesh-based LES. Wings and rotating blades are introduced in the computational domain through actuator line and actuator surface models. Simulations are coupled with an aeroacoustics solver to predict tonal and broadband noise radiated by rotors. The framework, called FLOWUnsteady, is hereby released as an open-source code and extensively validated. Validation studies published in previous work by the authors are summarized, showcasing rotors across operating conditions with a rotor in hover, propellers, a wind turbine, and two side-by-side rotors in hover. Validation of rotor-wing interactions is presented simulating a tailplane with tip-mounted propellers and a blown wing with propellers mounted mid-span. The capabilities of the framework are showcased through the simulation of a tiltwing eVTOL vehicle and an AWE wind-harvesting aircraft, featuring rotors with variable RPM, variable pitch, tilting of wings and rotors, non-trivial flight paths, and complex aerodynamic interactions.
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Helicopter Rotor Optimization via Operator Overloading-Based Discrete Adjoint Approach
A memory efficient framework is developed for the aerodynamic design optimization of helicopter rotor blades in hover. This framework is based on a fully-automated discrete-adjoint toolbox called FDOT. The in-house toolbox is capable of computing sensitivity or gradient information very accurately, and uses an operator-overloading technique that takes advantage of a unique expression-template-based approach for memory and computational efficiency while still being fully-automated with minimal user interventions. The main goal of the present work is to "design" helicopter rotor blades with increased figure-of-merit. Therefore, the flow around the Caradonna-Tung rotor in non-lifting and lifting hover conditions is studied in order to validate the primal and adjoint solvers based on a rotating frame of reference formulation. The efficacy of the optimization framework is first demonstrated for drag minimization of a rotating NACA 0012 airfoil, which resembles a Vertical-Axis Wind Turbine (VAWT) configuration. Finally, the single- and multi-point design optimization results for the Caradonna-Tung rotor are presented. It is important to note that the current approach (FDOT) can be directly coupled -- in a "black-box" manner -- to other existing codes in the Helios computational platform, which is part of CREATE-AV.
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- Award ID(s):
- 1803760
- NSF-PAR ID:
- 10280820
- Date Published:
- Journal Name:
- AIAA Scitech 2021 Forum
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.2514/6.2021-0170
