Design of an overset mesh methodology for forest protection aircraft droplet release
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Date
2015
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University of New Brunswick
Abstract
Canada's forests are exposed to persistent threats from insect outbreaks, which are mitigated by pesticides (and increasingly bio-pesticides) released from aircrafts. The trajectory of the pesticide droplets into a forest canopy is heavily influenced by the aircraft wake and atmospheric turbulence leading to a potential for off-target drift. Off-target drifts are subject to heavy environmental regulations, and buffer zones are required to adhere to the regulations, which restrict the target areas. Advanced aerial operators make use of spray drift models to predict the droplet trajectories into the canopy in advance and compensate for drift. The models are based on simplified analytic approaches for vortex swirling and atmospheric ground effects, and they do not adequately predict the spray distribution or deposition. A better evaluation of the spray droplet transport can be obtained with a full-physics representation using Computational Fluid Dynamics. This approach can be used to create a reliable database (relative to experiments) once proven to improve existing real-time spray drift models. The objective of the present work is to lay the ground work for the accomplishment of such a full-physics representation.
A full-physics CFD simulation with a single mesh is not possible without geometric changes or active mesh re-generation at each time-step due to the movement of the aircraft relative to a complex forest canopy. A method to resolve this issue is the use of an overset mesh, where the computational domain consists of separate, independent, nested mesh systems that can move relative to one another. Flow solution data is transferred between the meshes via interpolation at shared boundaries using a donor-receiver methodology. The implementation and demonstration of an overset methodology in the hybrid multicore-manycore EXN/Aero CFD software is one of the main objectives of this work. Another objective is the demonstration of an aircraft simulation. Both, the overset methodology and the knowledge gained by the aircraft simulation will be incorporated into the broad objectives of the research program.