The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow

Thomas A. Hafner, Jae Sung Park

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Reducing turbulent skin-friction drag is a subject of great interest due to the potential benefits. These benefits are reflected in applications such as aircraft and vehicles for which skin-friction drag constitutes a significant fraction of the total drag. For example, commercial airliners have up to 50% of their fuel consumption associated with turbulent drag. Thus, any drag reduction would result in substantial savings with regards to the operational cost of the airline industry. In this study, we investigated the effects of a spanwise body force on reducing skin-friction drag in turbulent channel flows. To this end, we performed direct numerical simulations (DNS) of turbulent channel flows with an applied spanwise body force. The body force consists of four control parameters: the amplitude of excitation, penetration depth, period of oscillation, and wavelength. A series of DNS were performed to investigate the effect of these parameters on drag reduction. We observed different levels of drag reduction and the magnitude of skin-friction varied considerably. The DNS results showed that the skin friction is reduced by as much as 20% with values for penetration lengths from 0.03 to 0.09 and periods between 10 and 20. An optimal combination of the four adjustable control parameters is yet to be concluded. In addition to skinfriction reduction, we found an intriguing observation from a time series of wall shear stress. When the wall shear stress is sufficiently lower than its mean value (i.e., low-drag intervals), the spanwise body force appears to significantly affect turbulent dynamics to make the wall shear stress not as chaotic as in other intervals. Specifically, the standard deviations of the peak-to-peak magnitudes of the wall shear stress during low-drag intervals are significantly lower than that of other intervals. This observation could be crucial in that it may lead to a further fundamental understanding of the drag reduction process. Moreover, it may aid in the development of more effective control schemes by way of anticipating that low-drag intervals are promising targets for drag reduction.

Original languageEnglish (US)
Title of host publicationFluids Engineering
PublisherAmerican Society of Mechanical Engineers (ASME)
ISBN (Electronic)9780791852101
DOIs
StatePublished - Jan 1 2018
EventASME 2018 International Mechanical Engineering Congress and Exposition, IMECE 2018 - Pittsburgh, United States
Duration: Nov 9 2018Nov 15 2018

Publication series

NameASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)
Volume7

Other

OtherASME 2018 International Mechanical Engineering Congress and Exposition, IMECE 2018
CountryUnited States
CityPittsburgh
Period11/9/1811/15/18

Fingerprint

Skin friction
Turbulent flow
Drag
Drag reduction
Shear stress
Direct numerical simulation
Channel flow
Fuel consumption
Time series
Aircraft
Wavelength

Keywords

  • Body force
  • Direct numerical simulation
  • Drag reduction process
  • Skinfriction reduction
  • Turbulence

ASJC Scopus subject areas

  • Mechanical Engineering

Cite this

Hafner, T. A., & Park, J. S. (2018). The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow. In Fluids Engineering (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE); Vol. 7). American Society of Mechanical Engineers (ASME). https://doi.org/10.1115/IMECE201886610

The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow. / Hafner, Thomas A.; Park, Jae Sung.

Fluids Engineering. American Society of Mechanical Engineers (ASME), 2018. (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE); Vol. 7).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Hafner, TA & Park, JS 2018, The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow. in Fluids Engineering. ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), vol. 7, American Society of Mechanical Engineers (ASME), ASME 2018 International Mechanical Engineering Congress and Exposition, IMECE 2018, Pittsburgh, United States, 11/9/18. https://doi.org/10.1115/IMECE201886610
Hafner TA, Park JS. The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow. In Fluids Engineering. American Society of Mechanical Engineers (ASME). 2018. (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)). https://doi.org/10.1115/IMECE201886610
Hafner, Thomas A. ; Park, Jae Sung. / The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow. Fluids Engineering. American Society of Mechanical Engineers (ASME), 2018. (ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)).
@inproceedings{7c6824d83e6b4af3802029ea53e289b7,
title = "The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow",
abstract = "Reducing turbulent skin-friction drag is a subject of great interest due to the potential benefits. These benefits are reflected in applications such as aircraft and vehicles for which skin-friction drag constitutes a significant fraction of the total drag. For example, commercial airliners have up to 50{\%} of their fuel consumption associated with turbulent drag. Thus, any drag reduction would result in substantial savings with regards to the operational cost of the airline industry. In this study, we investigated the effects of a spanwise body force on reducing skin-friction drag in turbulent channel flows. To this end, we performed direct numerical simulations (DNS) of turbulent channel flows with an applied spanwise body force. The body force consists of four control parameters: the amplitude of excitation, penetration depth, period of oscillation, and wavelength. A series of DNS were performed to investigate the effect of these parameters on drag reduction. We observed different levels of drag reduction and the magnitude of skin-friction varied considerably. The DNS results showed that the skin friction is reduced by as much as 20{\%} with values for penetration lengths from 0.03 to 0.09 and periods between 10 and 20. An optimal combination of the four adjustable control parameters is yet to be concluded. In addition to skinfriction reduction, we found an intriguing observation from a time series of wall shear stress. When the wall shear stress is sufficiently lower than its mean value (i.e., low-drag intervals), the spanwise body force appears to significantly affect turbulent dynamics to make the wall shear stress not as chaotic as in other intervals. Specifically, the standard deviations of the peak-to-peak magnitudes of the wall shear stress during low-drag intervals are significantly lower than that of other intervals. This observation could be crucial in that it may lead to a further fundamental understanding of the drag reduction process. Moreover, it may aid in the development of more effective control schemes by way of anticipating that low-drag intervals are promising targets for drag reduction.",
keywords = "Body force, Direct numerical simulation, Drag reduction process, Skinfriction reduction, Turbulence",
author = "Hafner, {Thomas A.} and Park, {Jae Sung}",
year = "2018",
month = "1",
day = "1",
doi = "10.1115/IMECE201886610",
language = "English (US)",
series = "ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)",
publisher = "American Society of Mechanical Engineers (ASME)",
booktitle = "Fluids Engineering",

}

TY - GEN

T1 - The effect of a spanwise body force on skin-friction reduction and its connections to low-drag states in turbulent flow

AU - Hafner, Thomas A.

AU - Park, Jae Sung

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Reducing turbulent skin-friction drag is a subject of great interest due to the potential benefits. These benefits are reflected in applications such as aircraft and vehicles for which skin-friction drag constitutes a significant fraction of the total drag. For example, commercial airliners have up to 50% of their fuel consumption associated with turbulent drag. Thus, any drag reduction would result in substantial savings with regards to the operational cost of the airline industry. In this study, we investigated the effects of a spanwise body force on reducing skin-friction drag in turbulent channel flows. To this end, we performed direct numerical simulations (DNS) of turbulent channel flows with an applied spanwise body force. The body force consists of four control parameters: the amplitude of excitation, penetration depth, period of oscillation, and wavelength. A series of DNS were performed to investigate the effect of these parameters on drag reduction. We observed different levels of drag reduction and the magnitude of skin-friction varied considerably. The DNS results showed that the skin friction is reduced by as much as 20% with values for penetration lengths from 0.03 to 0.09 and periods between 10 and 20. An optimal combination of the four adjustable control parameters is yet to be concluded. In addition to skinfriction reduction, we found an intriguing observation from a time series of wall shear stress. When the wall shear stress is sufficiently lower than its mean value (i.e., low-drag intervals), the spanwise body force appears to significantly affect turbulent dynamics to make the wall shear stress not as chaotic as in other intervals. Specifically, the standard deviations of the peak-to-peak magnitudes of the wall shear stress during low-drag intervals are significantly lower than that of other intervals. This observation could be crucial in that it may lead to a further fundamental understanding of the drag reduction process. Moreover, it may aid in the development of more effective control schemes by way of anticipating that low-drag intervals are promising targets for drag reduction.

AB - Reducing turbulent skin-friction drag is a subject of great interest due to the potential benefits. These benefits are reflected in applications such as aircraft and vehicles for which skin-friction drag constitutes a significant fraction of the total drag. For example, commercial airliners have up to 50% of their fuel consumption associated with turbulent drag. Thus, any drag reduction would result in substantial savings with regards to the operational cost of the airline industry. In this study, we investigated the effects of a spanwise body force on reducing skin-friction drag in turbulent channel flows. To this end, we performed direct numerical simulations (DNS) of turbulent channel flows with an applied spanwise body force. The body force consists of four control parameters: the amplitude of excitation, penetration depth, period of oscillation, and wavelength. A series of DNS were performed to investigate the effect of these parameters on drag reduction. We observed different levels of drag reduction and the magnitude of skin-friction varied considerably. The DNS results showed that the skin friction is reduced by as much as 20% with values for penetration lengths from 0.03 to 0.09 and periods between 10 and 20. An optimal combination of the four adjustable control parameters is yet to be concluded. In addition to skinfriction reduction, we found an intriguing observation from a time series of wall shear stress. When the wall shear stress is sufficiently lower than its mean value (i.e., low-drag intervals), the spanwise body force appears to significantly affect turbulent dynamics to make the wall shear stress not as chaotic as in other intervals. Specifically, the standard deviations of the peak-to-peak magnitudes of the wall shear stress during low-drag intervals are significantly lower than that of other intervals. This observation could be crucial in that it may lead to a further fundamental understanding of the drag reduction process. Moreover, it may aid in the development of more effective control schemes by way of anticipating that low-drag intervals are promising targets for drag reduction.

KW - Body force

KW - Direct numerical simulation

KW - Drag reduction process

KW - Skinfriction reduction

KW - Turbulence

UR - http://www.scopus.com/inward/record.url?scp=85060382770&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85060382770&partnerID=8YFLogxK

U2 - 10.1115/IMECE201886610

DO - 10.1115/IMECE201886610

M3 - Conference contribution

AN - SCOPUS:85060382770

T3 - ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

BT - Fluids Engineering

PB - American Society of Mechanical Engineers (ASME)

ER -