Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development

The interaction of a helicopter rotor with the ground in hover flight is addressed numerically using a hybrid Eulerian–Lagrangian CFD model. When a helicopter takes off or lands, its wake interferes with the ground. This interaction, depending on the height-to-rotor diameter ratio, causes the alteri...

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Autores principales:	Theologos Andronikos, George Papadakis, Vasilis Riziotis, Spyros Voutsinas
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	ground boundary layer helicopter ground effect Eulerian-Lagrangian methods Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/f91ba0d776cf426fb19668da185f4e41
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spelling	oai:doaj.org-article:f91ba0d776cf426fb19668da185f4e412021-11-11T15:01:57ZRevising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development10.3390/app112199352076-3417https://doaj.org/article/f91ba0d776cf426fb19668da185f4e412021-10-01T00:00:00Zhttps://www.mdpi.com/2076-3417/11/21/9935https://doaj.org/toc/2076-3417The interaction of a helicopter rotor with the ground in hover flight is addressed numerically using a hybrid Eulerian–Lagrangian CFD model. When a helicopter takes off or lands, its wake interferes with the ground. This interaction, depending on the height-to-rotor diameter ratio, causes the altering of the rotor loading and performance as compared to the unconstrained case and gives rise to the development of a complex outwash flow field in the surrounding of the helicopter. The present study aims to characterize the interactional phenomena occurring in the early stages of the rotor wake development and in particular the interference of the starting vortex with the ground boundary layer and the effect of this interaction in the motion of the vortex in the rotor outwash flow. The hybrid CFD method employed combines a standard URANS compressible finite volume solver, the use of which is restricted to confined grids around solid bodies, and a Lagrangian approximation of the entire flow field in which conservation equations are solved in their material form, disctretized using particle representation of the flow quantities. The two methods are strongly coupled to each other through an appropriate iterative scheme. The main advantage of the proposed methodology is that it can conveniently handle complex configurations with several bodies that move independently from one another, with affordable computational cost. In this paper, thrust coefficient predictions of the hybrid model are compared to predictions of a free wake code and to experimental data indicating that consistent prediction of the rotor load requires the inclusion of the ground boundary layer in the analysis. Moreover, detailed comparisons of the rotor wake evolution predicted by the hybrid model are presented.Theologos AndronikosGeorge PapadakisVasilis RiziotisSpyros VoutsinasMDPI AGarticleground boundary layerhelicopterground effectEulerian-Lagrangian methodsTechnologyTEngineering (General). Civil engineering (General)TA1-2040Biology (General)QH301-705.5PhysicsQC1-999ChemistryQD1-999ENApplied Sciences, Vol 11, Iss 9935, p 9935 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	ground boundary layer helicopter ground effect Eulerian-Lagrangian methods Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999
spellingShingle	ground boundary layer helicopter ground effect Eulerian-Lagrangian methods Technology T Engineering (General). Civil engineering (General) TA1-2040 Biology (General) QH301-705.5 Physics QC1-999 Chemistry QD1-999 Theologos Andronikos George Papadakis Vasilis Riziotis Spyros Voutsinas Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
description	The interaction of a helicopter rotor with the ground in hover flight is addressed numerically using a hybrid Eulerian–Lagrangian CFD model. When a helicopter takes off or lands, its wake interferes with the ground. This interaction, depending on the height-to-rotor diameter ratio, causes the altering of the rotor loading and performance as compared to the unconstrained case and gives rise to the development of a complex outwash flow field in the surrounding of the helicopter. The present study aims to characterize the interactional phenomena occurring in the early stages of the rotor wake development and in particular the interference of the starting vortex with the ground boundary layer and the effect of this interaction in the motion of the vortex in the rotor outwash flow. The hybrid CFD method employed combines a standard URANS compressible finite volume solver, the use of which is restricted to confined grids around solid bodies, and a Lagrangian approximation of the entire flow field in which conservation equations are solved in their material form, disctretized using particle representation of the flow quantities. The two methods are strongly coupled to each other through an appropriate iterative scheme. The main advantage of the proposed methodology is that it can conveniently handle complex configurations with several bodies that move independently from one another, with affordable computational cost. In this paper, thrust coefficient predictions of the hybrid model are compared to predictions of a free wake code and to experimental data indicating that consistent prediction of the rotor load requires the inclusion of the ground boundary layer in the analysis. Moreover, detailed comparisons of the rotor wake evolution predicted by the hybrid model are presented.
format	article
author	Theologos Andronikos George Papadakis Vasilis Riziotis Spyros Voutsinas
author_facet	Theologos Andronikos George Papadakis Vasilis Riziotis Spyros Voutsinas
author_sort	Theologos Andronikos
title	Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
title_short	Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
title_full	Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
title_fullStr	Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
title_full_unstemmed	Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development
title_sort	revising of the near ground helicopter hover: the effect of ground boundary layer development
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/f91ba0d776cf426fb19668da185f4e41
work_keys_str_mv	AT theologosandronikos revisingoftheneargroundhelicopterhovertheeffectofgroundboundarylayerdevelopment AT georgepapadakis revisingoftheneargroundhelicopterhovertheeffectofgroundboundarylayerdevelopment AT vasilisriziotis revisingoftheneargroundhelicopterhovertheeffectofgroundboundarylayerdevelopment AT spyrosvoutsinas revisingoftheneargroundhelicopterhovertheeffectofgroundboundarylayerdevelopment
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Revising of the Near Ground Helicopter Hover: The Effect of Ground Boundary Layer Development

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