Computational Characterization of Unsteadiness and Turbulence in Rotor Hub Wakes

Forrest J. Mobley; Tristan D. Wall; James G. Coder

doi:10.4050/JAHS.68.012007

Computational Characterization of Unsteadiness and Turbulence in Rotor Hub Wakes

Forrest J. Mobley, Tristan D. Wall, James G. Coder

Aerospace Engineering

Research output: Contribution to journal › Article › peer-review

Abstract

Reynolds stresses and turbulent kinetic energy are studied in the wakes of several helicopter rotor hub geometries in forward flight. Computational fluid dynamics simulations are performed using NASA’s OVERFLOW 2.2n Reynolds-averaged Navier–Stokes solver. The simulations impose flow conditions based on previous and current experimental and numerical studies. Discrete Fourier transforms are used to examine velocity harmonics for several frequencies and compared against available experimental results. Components of the Reynolds stress tensor are computed and examined. Production and transport of the turbulent kinetic energy are examined through the rotor hub wakes at six streamwise coordinates. It was found that the scissor arms, previously found to have a significant effect on rotor hub force harmonics, also had a significant effect on the magnitudes of Reynolds stresses and turbulent kinetic energy. Integrated values of turbulent kinetic energy flux indicate that drag-reducing designs have a direct effect on turbulent kinetic energy levels in the wake.

Original language	English (US)
Article number	012007
Journal	Journal of the American Helicopter Society
Volume	68
Issue number	1
DOIs	https://doi.org/10.4050/JAHS.68.012007
State	Published - Jan 2023

All Science Journal Classification (ASJC) codes

General Materials Science
Aerospace Engineering
Mechanics of Materials
Mechanical Engineering

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10.4050/JAHS.68.012007

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title = "Computational Characterization of Unsteadiness and Turbulence in Rotor Hub Wakes",

abstract = "Reynolds stresses and turbulent kinetic energy are studied in the wakes of several helicopter rotor hub geometries in forward flight. Computational fluid dynamics simulations are performed using NASA{\textquoteright}s OVERFLOW 2.2n Reynolds-averaged Navier–Stokes solver. The simulations impose flow conditions based on previous and current experimental and numerical studies. Discrete Fourier transforms are used to examine velocity harmonics for several frequencies and compared against available experimental results. Components of the Reynolds stress tensor are computed and examined. Production and transport of the turbulent kinetic energy are examined through the rotor hub wakes at six streamwise coordinates. It was found that the scissor arms, previously found to have a significant effect on rotor hub force harmonics, also had a significant effect on the magnitudes of Reynolds stresses and turbulent kinetic energy. Integrated values of turbulent kinetic energy flux indicate that drag-reducing designs have a direct effect on turbulent kinetic energy levels in the wake.",

author = "Mobley, {Forrest J.} and Wall, {Tristan D.} and Coder, {James G.}",

note = "Funding Information: This research was partially funded by the U.S. Army{\textquoteright}s National Rotorcraft Technology Center program, an effort sponsored by the U.S. Government under Other Transaction number W15QKN-10-9-0003 between Vertical Lift Consortium, Inc. and the Government, and by the Government under Agreement No. W911W6-17-2-0003. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the U.S. Government. Some images in this paper were created using FieldView, licenses for which were provided through the FieldView University Partners Program. Publisher Copyright: {\textcopyright} 2023 Vertical Flight Society.",

year = "2023",

month = jan,

doi = "10.4050/JAHS.68.012007",

language = "English (US)",

volume = "68",

journal = "Journal of the American Helicopter Society",

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PY - 2023/1

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N2 - Reynolds stresses and turbulent kinetic energy are studied in the wakes of several helicopter rotor hub geometries in forward flight. Computational fluid dynamics simulations are performed using NASA’s OVERFLOW 2.2n Reynolds-averaged Navier–Stokes solver. The simulations impose flow conditions based on previous and current experimental and numerical studies. Discrete Fourier transforms are used to examine velocity harmonics for several frequencies and compared against available experimental results. Components of the Reynolds stress tensor are computed and examined. Production and transport of the turbulent kinetic energy are examined through the rotor hub wakes at six streamwise coordinates. It was found that the scissor arms, previously found to have a significant effect on rotor hub force harmonics, also had a significant effect on the magnitudes of Reynolds stresses and turbulent kinetic energy. Integrated values of turbulent kinetic energy flux indicate that drag-reducing designs have a direct effect on turbulent kinetic energy levels in the wake.

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Computational Characterization of Unsteadiness and Turbulence in Rotor Hub Wakes

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