The flow physics of helicopter brownout

Catriona Phillips, Hyo Wan Kim, R.E. Brown

Research output: Contribution to conferencePaper

Abstract

The formation of the dust cloud that is associated with low-level helicopter operations in desert environments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the flow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to explain the formation of characteristic sheet- and filament-like structures in the dust cloud in terms of the interactions between individual vortical filaments and the ground. In parts of the flow, for instance near the ground vortex that is formed under the leading edge of the rotor when in forward flight, the dust cloud becomes more space-filling than sheet-like in character, and the theory suggests that this is a result of the dust distribution having been processed by multiple vortices over a significant period of time. The distribution of the regions on the ground plane from which significant entrainment of dust into the flow takes place is shown to be influenced strongly by the unstable nature of the vortical structures within the flow. It is suggested that the effect of this vortical instability, when integrated over the timescales that are characteristic of the formation of the dust cloud, is to de-sensitize the gross characteristics of the dustcloud to the details of the wake structure at its inception on the rotor blades. This suggests that the formation of the brownout cloud may be relatively insensitive to the detailed design of the blades of the rotors and may thus be influenced only by less subtle characteristics of the helicopter system.

Conference

Conference66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology
CityPhoenix, Arizona
Period11/05/1013/05/10

Fingerprint

Helicopter
Helicopters
Dust
Physics
Rotor
Entrainment
Filament
Blade
Rotors
Vortex
Turbomachine blades
Vortex flow
Particulate Matter
Coupled Model
Thin Layer
Wake
Gross
Period of time
Vorticity
Time Scales

Keywords

  • vorticity transport model
  • numerical modelling
  • vortical instability
  • brownout dust cloud

Cite this

Phillips, C., Kim, H. W., & Brown, R. E. (2010). The flow physics of helicopter brownout. Paper presented at 66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology, Phoenix, Arizona, .
Phillips, Catriona ; Kim, Hyo Wan ; Brown, R.E. / The flow physics of helicopter brownout. Paper presented at 66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology, Phoenix, Arizona, .
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abstract = "The formation of the dust cloud that is associated with low-level helicopter operations in desert environments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the flow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to explain the formation of characteristic sheet- and filament-like structures in the dust cloud in terms of the interactions between individual vortical filaments and the ground. In parts of the flow, for instance near the ground vortex that is formed under the leading edge of the rotor when in forward flight, the dust cloud becomes more space-filling than sheet-like in character, and the theory suggests that this is a result of the dust distribution having been processed by multiple vortices over a significant period of time. The distribution of the regions on the ground plane from which significant entrainment of dust into the flow takes place is shown to be influenced strongly by the unstable nature of the vortical structures within the flow. It is suggested that the effect of this vortical instability, when integrated over the timescales that are characteristic of the formation of the dust cloud, is to de-sensitize the gross characteristics of the dustcloud to the details of the wake structure at its inception on the rotor blades. This suggests that the formation of the brownout cloud may be relatively insensitive to the detailed design of the blades of the rotors and may thus be influenced only by less subtle characteristics of the helicopter system.",
keywords = "vorticity transport model, numerical modelling, vortical instability, brownout dust cloud",
author = "Catriona Phillips and Kim, {Hyo Wan} and R.E. Brown",
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language = "English",
note = "66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology ; Conference date: 11-05-2010 Through 13-05-2010",

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Phillips, C, Kim, HW & Brown, RE 2010, 'The flow physics of helicopter brownout' Paper presented at 66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology, Phoenix, Arizona, 11/05/10 - 13/05/10, .

The flow physics of helicopter brownout. / Phillips, Catriona; Kim, Hyo Wan; Brown, R.E.

2010. Paper presented at 66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology, Phoenix, Arizona, .

Research output: Contribution to conferencePaper

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T1 - The flow physics of helicopter brownout

AU - Phillips, Catriona

AU - Kim, Hyo Wan

AU - Brown, R.E.

PY - 2010/5/11

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N2 - The formation of the dust cloud that is associated with low-level helicopter operations in desert environments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the flow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to explain the formation of characteristic sheet- and filament-like structures in the dust cloud in terms of the interactions between individual vortical filaments and the ground. In parts of the flow, for instance near the ground vortex that is formed under the leading edge of the rotor when in forward flight, the dust cloud becomes more space-filling than sheet-like in character, and the theory suggests that this is a result of the dust distribution having been processed by multiple vortices over a significant period of time. The distribution of the regions on the ground plane from which significant entrainment of dust into the flow takes place is shown to be influenced strongly by the unstable nature of the vortical structures within the flow. It is suggested that the effect of this vortical instability, when integrated over the timescales that are characteristic of the formation of the dust cloud, is to de-sensitize the gross characteristics of the dustcloud to the details of the wake structure at its inception on the rotor blades. This suggests that the formation of the brownout cloud may be relatively insensitive to the detailed design of the blades of the rotors and may thus be influenced only by less subtle characteristics of the helicopter system.

AB - The formation of the dust cloud that is associated with low-level helicopter operations in desert environments has been simulated using the Vorticity Transport Model together with a coupled model to represent the entrainment and subsequent transport of particulate matter through the flow. A simple thin-layer theory, supported by simulations performed using the more physically-representative numerical model, is used to explain the formation of characteristic sheet- and filament-like structures in the dust cloud in terms of the interactions between individual vortical filaments and the ground. In parts of the flow, for instance near the ground vortex that is formed under the leading edge of the rotor when in forward flight, the dust cloud becomes more space-filling than sheet-like in character, and the theory suggests that this is a result of the dust distribution having been processed by multiple vortices over a significant period of time. The distribution of the regions on the ground plane from which significant entrainment of dust into the flow takes place is shown to be influenced strongly by the unstable nature of the vortical structures within the flow. It is suggested that the effect of this vortical instability, when integrated over the timescales that are characteristic of the formation of the dust cloud, is to de-sensitize the gross characteristics of the dustcloud to the details of the wake structure at its inception on the rotor blades. This suggests that the formation of the brownout cloud may be relatively insensitive to the detailed design of the blades of the rotors and may thus be influenced only by less subtle characteristics of the helicopter system.

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Phillips C, Kim HW, Brown RE. The flow physics of helicopter brownout. 2010. Paper presented at 66th American Helicopter Society Forum: Rising to New Heights in Vertical Lift Technology, Phoenix, Arizona, .