Brownout modeling

Rovere, Federico (2023) Brownout modeling. PhD thesis, University of Glasgow.

Abstract

The thesis compares different computational approaches for simulate brownout clouds. Brownout relates to blinding dust clouds stirred up by the helicopter rotor downwash during near-ground flight. This causes significant flight safety risks, including ground obstacle collisions and dynamic rollover due to sloped and uneven terrain. Operating helicopters in brownout conditions is very dangerous and has claimed many lives.

Due to the complexity of these phenomena, and the safety issues they may generate, brownout has been studied using different approaches, both numerical and experimental. In terms of the computational investigations: brownout works may be divided into the two approaches used to predict the dust cloud: Lagrangian and Eulerian.

A direct comparison of the two models s is presented in the same framework, to define the best practice for brownout predictions. The present work involved the development of a Lagrangian particle tracking algorithm and an Eulerian model in the HMB3 (Helicopter Multi Block) framework. Brownout clouds obtained with these models are compared with experimental results and between them. Results show that even if in proximity to a rotor, the accuracy of the two models is comparable, further from it the Lagrangian approach is more accurate than modelling based on the Eulerian approach.

Furthermore, the two models are compared in terms of computational efficiency, and results show how Eulerian is a better model to predict brownout, due to its intrinsic abilities not to being affected in its computational efficiency by the amount of particles.

In addition, brownout clouds are compared in terms of size at different rotor configurations. Results show how rotors with higher thrust coefficient are able to generate the more dangerous scenarios, generating bigger clouds than rotors operating at lower thrust coefficients. The presence of the fuselage has also been studied, comparing cases with and without it.

The thesis includes more safety aspects, including risks posed to ground personnel and nearby structures due to the strong outflow generated by hovering and taxiing rotorcraft. In this work, an analysis of safety operations is performed in terms of forces that ground personnel may
suffer due to strong rotor outflows. Force distribution over the human body and total force are computed from the resolved flowfield around a rotor. Different single rotor configurations have been taken into account, and in all cases considered, the whole area around the rotor can be considered safe according to military-based thresholds.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Funded through the European Union’s H2020 research and innovation programme under the Marie Sktodowska-Curie grant agreement No 721920.
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering > Autonomous Systems and Connectivity
• Supervisor's Name: Steijl, Dr. Rene and Barakos, Professor George
• Date of Award: 2023
• Depositing User: Theses Team
• Unique ID: glathesis:2023-83704
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 05 Jul 2023 10:20
• Last Modified: 07 Jul 2023 08:04
• Thesis DOI: 10.5525/gla.thesis.83704
• URI: https://theses.gla.ac.uk/id/eprint/83704

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