Helicopter flight in the airwake of non-aviation ships
Helicopter flight in the airwake of non-aviation ships
There are problems specific to the helicopter/ship dynamic interface, which limit helicopter operations. Amongst these is the difficulty associated with landing on a moving platform. The ship airwake, which includes large velocity gradients and areas of turbulence, is considered a crucial factor in limiting these operations. For this reason knowledge of the air flow around the ship and through the helicopter's rotors is necessary to understand the problems the helicopter encounters as it lands and takes off.
A CFD model of a hovering helicopter main rotor is developed to examine airflow in the presence of ship structures and side winds. The rotor is modelled by modifying the governing Navier-Stokes equations in the region of the disc. The extra terms added to the governing equations apply a downforce to the fluid; these forces are independent of the flow around the rotor and equal to the helicopter weight. The boundaries of the computational domain are also modified in order to generate a physically correct solution. Flow solutions in both two and three dimensions are achieved using the commercial flow solver CFX. The flow solutions exhibit very good correlation with established momentum and power principles. The rotor model is also flown in steady horizontal flight. The resultant flow solutions agree with theoretical flow fields thus proving the validity of the rotor model.
An extensive sensitivity study of CFD grid and solver parameters is also presented. This ensures that all flow solutions achieved are of the highest fidelity but are reached in a computationally efficient manner. The turbulence models are adjusted to produce solutions which agree with wind tunnel data. CFD flow solutions are presented which correspond to full-scale version of experimental studies on bluff bodies in wind tunnels. The results show that qualitative features of the wind tunnel flow regimes are recognised and resolved by the computational solution. The CFD also agrees with the quantitative data where available.
Finally the helicopter rotor model and the ship model are combined to yield one flow solution, which cannot be achieved by superposition. The resultant flow yields valuable data about the induced velocities at the rotor which ultimately determine the control pitch and power required to maintain the hover in a given location.
University of Southampton
Wakefield, Nigel Hugh
db9752ef-e97b-446b-9c0c-cb5c08e6e663
2000
Wakefield, Nigel Hugh
db9752ef-e97b-446b-9c0c-cb5c08e6e663
Wakefield, Nigel Hugh
(2000)
Helicopter flight in the airwake of non-aviation ships.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
There are problems specific to the helicopter/ship dynamic interface, which limit helicopter operations. Amongst these is the difficulty associated with landing on a moving platform. The ship airwake, which includes large velocity gradients and areas of turbulence, is considered a crucial factor in limiting these operations. For this reason knowledge of the air flow around the ship and through the helicopter's rotors is necessary to understand the problems the helicopter encounters as it lands and takes off.
A CFD model of a hovering helicopter main rotor is developed to examine airflow in the presence of ship structures and side winds. The rotor is modelled by modifying the governing Navier-Stokes equations in the region of the disc. The extra terms added to the governing equations apply a downforce to the fluid; these forces are independent of the flow around the rotor and equal to the helicopter weight. The boundaries of the computational domain are also modified in order to generate a physically correct solution. Flow solutions in both two and three dimensions are achieved using the commercial flow solver CFX. The flow solutions exhibit very good correlation with established momentum and power principles. The rotor model is also flown in steady horizontal flight. The resultant flow solutions agree with theoretical flow fields thus proving the validity of the rotor model.
An extensive sensitivity study of CFD grid and solver parameters is also presented. This ensures that all flow solutions achieved are of the highest fidelity but are reached in a computationally efficient manner. The turbulence models are adjusted to produce solutions which agree with wind tunnel data. CFD flow solutions are presented which correspond to full-scale version of experimental studies on bluff bodies in wind tunnels. The results show that qualitative features of the wind tunnel flow regimes are recognised and resolved by the computational solution. The CFD also agrees with the quantitative data where available.
Finally the helicopter rotor model and the ship model are combined to yield one flow solution, which cannot be achieved by superposition. The resultant flow yields valuable data about the induced velocities at the rotor which ultimately determine the control pitch and power required to maintain the hover in a given location.
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Published date: 2000
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Local EPrints ID: 464226
URI: http://eprints.soton.ac.uk/id/eprint/464226
PURE UUID: 09c110f6-963b-41fb-9c8a-1f339e61d0f1
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Date deposited: 04 Jul 2022 21:39
Last modified: 16 Mar 2024 19:21
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Author:
Nigel Hugh Wakefield
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