Unsteady Panel Method (UPM)
UPM is a fast mid-fidelity tool for rotorcraft aerodynamics. It is based on an unsteady 3D panel method with a "free-wake" method or a particle method for modeling the wake of wings and rotors. Viscous effects such as friction forces and separation areas can be predicted using boundary layer methods. All computationally intensive program parts are parallelized with OpenMP and are optimised for fast execution times.
UPM allows for performing complex unsteady simulations of complete helicopters or new eVTOL (= air taxi) configurations while requiring only a fraction of the effort needed by high-fidelity CFD simulations. Still, it is able to capture many aerodynamic interaction effects.
Key features
- unsteady 3D panel method with free-wake
- wake models based on wake panels with viscous cortex core, blade tip vortex rollup model (optional) or viscous vortex particles (optional)
- approximate boundary layer analysis
- performant implementation including OpenMP parallelization and fast multipole method (FMM) for wake induced velocities
- flexible hierarchical prescription of rigid body motion and deformations
- numerous postprocessing options included (e.g. unsteady loads, wake geometry, boundary layer properties)
Area of Application
Typical applications include preliminary investigations of flight performance, studies for aerodynamic interactions (e.g. rotor-rotor interactions, rotor-wing interactions), multidisciplinary coupled simulations including flight mechanics and structural dynamics methods, and aeroacoustic prediction of rotor noise (focusing on blade-vortex interaction noise). For example, UPM was successfully used to optimise the tail geometry of a new helicopter considering the main rotor downwash, and to analyze the noise of the novel high-speed helicopter RACER. Nevertheless, one should always be aware of the limitations of the underlying theories (incompressible, inviscid flow) when using UPM.
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