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The effect of turboprop propulsion on the aerodynamic benefits of formation flight
In order to determine the effect of turboprop propulsion on the aerodynamic benefits of formation flight, a 3D Vortex Filament Method (VFM) programme, which made use of a Burnham-Hallock viscous core model, was formulated and employed to model the progression and interaction of the wing and turbopro...
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| Format: | Thesis |
| Language: | English |
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Department of Mechanical Engineering
2017
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| _version_ | 1867613299611271168 |
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| access_status_str | Open Access |
| author | McKenzie, Cameron Cedric |
| author2 | Redelinghuys, Christiaan |
| author_browse | McKenzie, Cameron Cedric Redelinghuys, Christiaan |
| author_facet | Redelinghuys, Christiaan McKenzie, Cameron Cedric |
| author_sort | McKenzie, Cameron Cedric |
| collection | Thesis |
| description | In order to determine the effect of turboprop propulsion on the aerodynamic benefits of formation flight, a 3D Vortex Filament Method (VFM) programme, which made use of a Burnham-Hallock viscous core model, was formulated and employed to model the progression and interaction of the wing and turboprop trailing wakes. Within this programme, an initial prescribed wake for the turboprop engines was discretised by shed helicoidal vortex filaments generated by the use of an amalgamation of the propeller theory of Goldstein and Theodorsen. The downwash velocity field of a B747 during cruise, obtained via the use of the VFM Burnham-Hallock (VFM B-H) model programme, was verified against both the simulation conducted by Ehret and Oertel, in which an integrated Biot-Savart law VFM was utilised, as well as against experimental results obtained by Burnham et al. in their ground-based measurements of the wake vortex characteristics of a B747 aircraft. The VFM B-H model produced peak upwash and downwash velocities which matched those obtained by Ehret and Oertel to within 95% accuracy. Furthermore, a distance of 47.48 m between the rolled up vortex centres was achieved utilising the programmed VFM B-H model, which differed from the Ehret and Oertel model by only 0.48 m. Qualitatively, the 3D VFM B-H plot displayed similar degrees of roll-up and descent when compared to their Biot-Savart VFM plot. As a result of this positive validation process, the programmed VFM B-H model was utilised to simulate turboprop aircraft wakes of a higher complexity. In order to compare the effects of the number of turboprop engines on the aerodynamic benefits of formation flight, the three-bladed single turboprop engine Lancair Propjet, the six-bladed twin turboprop engine ATR 72 and the four-bladed four engine Lockheed Martin P-3 Orion were selected for comparative simulations. As extended formation flight makes use of aircraft downstream separation distances of more than ten wingspans, a wake length of 330 m (which equates to 10.9 span lengths for the P-3 Orion, 12.4 span lengths for the ATR 72 and 36.3 span lengths for the Lancair Propjet) was selected. All aircraft were simulated via the use of the VFM B-H model programme for a range of flight states from cruise conditions to zero g wing loading with full propeller thrust, such as in vertical ascents. From said simulations a novel viscous core radius to simulation convergence relationship equation was developed. The induced velocity fields at 330 m downstream in the wake were then generated in order to investigate the effects of the inclusion of turboprop engines on the aerodynamic benefits of formation flight. From said downwash plots, it was found that the helicoidal vortices affected that region of the wake within an average value of 35% of the wingspan, measured from the fuselage symmetry plane, for all simulated aircraft. In aircraft design, wing mounted engines are placed in a more inboard position in order to reduce rudder strength requirements as well as to minimize the yawing moment due to asymmetric thrust in the event of an engine failure. These helicoidal vortices' areas of influence are a result of said aircraft design convention as well as the helicoidal vortex sheets having a much lower vortex strength and filament density than the wing wake. The regions of the wing wake dominated by upwash induced velocities are outboard of an average value of 40% of the wingspan, measured from the fuselage symmetry plane. It is this region in which the drag reduction, fuel saving benefits of extended formation flight are harnessed. Therefore, as a result of aircraft engine mounting convention and marginal outboard drift of the helicoidal vortices, the turboprops' helicoidal vortices have minimal to negligible effect on the 10% wing overlap outboard-most region that sees positive fuel savings of 10% to 16% for previous extended formation flight investigations. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/25417 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:55.830Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Department of Mechanical Engineering |
| publisherStr | Department of Mechanical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/25417 The effect of turboprop propulsion on the aerodynamic benefits of formation flight McKenzie, Cameron Cedric Redelinghuys, Christiaan Mechanical Engineering In order to determine the effect of turboprop propulsion on the aerodynamic benefits of formation flight, a 3D Vortex Filament Method (VFM) programme, which made use of a Burnham-Hallock viscous core model, was formulated and employed to model the progression and interaction of the wing and turboprop trailing wakes. Within this programme, an initial prescribed wake for the turboprop engines was discretised by shed helicoidal vortex filaments generated by the use of an amalgamation of the propeller theory of Goldstein and Theodorsen. The downwash velocity field of a B747 during cruise, obtained via the use of the VFM Burnham-Hallock (VFM B-H) model programme, was verified against both the simulation conducted by Ehret and Oertel, in which an integrated Biot-Savart law VFM was utilised, as well as against experimental results obtained by Burnham et al. in their ground-based measurements of the wake vortex characteristics of a B747 aircraft. The VFM B-H model produced peak upwash and downwash velocities which matched those obtained by Ehret and Oertel to within 95% accuracy. Furthermore, a distance of 47.48 m between the rolled up vortex centres was achieved utilising the programmed VFM B-H model, which differed from the Ehret and Oertel model by only 0.48 m. Qualitatively, the 3D VFM B-H plot displayed similar degrees of roll-up and descent when compared to their Biot-Savart VFM plot. As a result of this positive validation process, the programmed VFM B-H model was utilised to simulate turboprop aircraft wakes of a higher complexity. In order to compare the effects of the number of turboprop engines on the aerodynamic benefits of formation flight, the three-bladed single turboprop engine Lancair Propjet, the six-bladed twin turboprop engine ATR 72 and the four-bladed four engine Lockheed Martin P-3 Orion were selected for comparative simulations. As extended formation flight makes use of aircraft downstream separation distances of more than ten wingspans, a wake length of 330 m (which equates to 10.9 span lengths for the P-3 Orion, 12.4 span lengths for the ATR 72 and 36.3 span lengths for the Lancair Propjet) was selected. All aircraft were simulated via the use of the VFM B-H model programme for a range of flight states from cruise conditions to zero g wing loading with full propeller thrust, such as in vertical ascents. From said simulations a novel viscous core radius to simulation convergence relationship equation was developed. The induced velocity fields at 330 m downstream in the wake were then generated in order to investigate the effects of the inclusion of turboprop engines on the aerodynamic benefits of formation flight. From said downwash plots, it was found that the helicoidal vortices affected that region of the wake within an average value of 35% of the wingspan, measured from the fuselage symmetry plane, for all simulated aircraft. In aircraft design, wing mounted engines are placed in a more inboard position in order to reduce rudder strength requirements as well as to minimize the yawing moment due to asymmetric thrust in the event of an engine failure. These helicoidal vortices' areas of influence are a result of said aircraft design convention as well as the helicoidal vortex sheets having a much lower vortex strength and filament density than the wing wake. The regions of the wing wake dominated by upwash induced velocities are outboard of an average value of 40% of the wingspan, measured from the fuselage symmetry plane. It is this region in which the drag reduction, fuel saving benefits of extended formation flight are harnessed. Therefore, as a result of aircraft engine mounting convention and marginal outboard drift of the helicoidal vortices, the turboprops' helicoidal vortices have minimal to negligible effect on the 10% wing overlap outboard-most region that sees positive fuel savings of 10% to 16% for previous extended formation flight investigations. 2017-09-26T14:58:43Z 2017-09-26T14:58:43Z 2017 Master Thesis Masters MSc (Eng) http://hdl.handle.net/11427/25417 eng application/pdf Department of Mechanical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Mechanical Engineering McKenzie, Cameron Cedric The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| thesis_degree_str | Master's |
| title | The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| title_full | The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| title_fullStr | The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| title_full_unstemmed | The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| title_short | The effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| title_sort | effect of turboprop propulsion on the aerodynamic benefits of formation flight |
| topic | Mechanical Engineering |
| url | http://hdl.handle.net/11427/25417 |
| work_keys_str_mv | AT mckenziecameroncedric theeffectofturboproppropulsionontheaerodynamicbenefitsofformationflight AT mckenziecameroncedric effectofturboproppropulsionontheaerodynamicbenefitsofformationflight |