Henriquez Huecas, Sergio
(2023)
Modelling of Airwake Hazards for Helicopter Flight Simulation.
PhD thesis, University of Liverpool.
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Abstract
This thesis summarises the work performed in the use of flight simulation to assess the impact of wake encounters and turbulence on the safety of helicopter operations. An initial literature search is presented, revealing a lack of previous research regarding the impact of wind turbine wakes on helicopter operations and a lack of accurate and easy to implement modelling tools for the assessment of the impact of turbulence on rotorcraft handling. The work is divided in two main parts: In the first part, following a literature review, results of flight simulation tests representing the accidental crossing of a wind turbine wake by a helicopter are presented. Encounters are of a ‘mild’ severity, flight safety was not compromised and resulted mainly in excursions in the yaw axis and deviations in roll. The pilot workload required in the recovery of from the initial encounter was strongly related to the aircraft’s handling qualities, especially yaw to pitch and yaw to roll cross couplings. The second part of the thesis details the development and implementation of a new turbulence modelling method for flight simulation. The model is based on an adaptation of a synthetic eddy method (SEM). It generates a random turbulence field surrounding the aircraft by filling a control volume with turbulence generating eddies which are displaced by ambient flow; this is the first time this type of modelling has been implemented in real-time piloted flight simulation. The induced turbulence automatically cross correlates disturbances across all aircraft elements and can be adjusted by changing strength, shape and size of eddies and combining series of eddies with different properties. Average frequency of the induced turbulence is proportional to the cube root of the number of eddies; increasing the frequency results in increased computational costs. Nevertheless, the SEM turbulence generator can produce real time disturbances within the 0.1 – 1Hz frequency range which has the most impact on pilot workload. Offline and piloted simulation was used to evaluate the model and compare against a precomputed wake using a Mann turbulence model. Results show that SEM induced turbulence can impact handling in similar manners as the precomputed wake, while offering random turbulence in real time.
| Item Type: | Thesis (PhD) |
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| Uncontrolled Keywords: | flight handling qualities, flight simulation, rotorcraft, turbulence modelling, wake encounters |
| Divisions: | Faculty of Science and Engineering > School of Engineering |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 14 Aug 2023 13:22 |
| Last Modified: | 14 Aug 2023 13:22 |
| DOI: | 10.17638/03169783 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3169783 |
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