Turbulence statistics in smooth wall oscillatory boundary layer flow

Research output: Contribution to journalArticle

4 Citations (Scopus)
4 Downloads (Pure)

Abstract

Turbulence characteristics of an asymmetric oscillatory boundary layer flow are analysed through two-component laser-Doppler measurements carried out in a large oscillatory flow tunnel and direct numerical simulation (DNS). Five different Reynolds numbers, , in the range 846–2057 have been investigated experimentally, where with the maximum oscillatory velocity in the irrotational region, the Stokes length and the fluid kinematic viscosity. DNS has been carried out for the lowest three equal to 846, 1155 and 1475. Both experimental and numerical results show that the flow statistics increase during accelerating phases of the flow and especially at times of transition to turbulent flow. Once turbulence is fully developed, the near-wall statistics remain almost constant until the late half-cycle, with values close to those reported for steady wall-bounded flows. The higher-order statistics reach large values within a normalized wall distance of approximately at phases corresponding to the onset of low-speed streak breaking, because of the intermittency of the velocity fluctuations at these times. In particular, the flatness of the streamwise velocity fluctuations reaches values of the order of ten, while the flatness of the wall-normal velocity fluctuations reaches values of several hundreds. Far from the wall, at locations where the vertical gradient of the streamwise velocity is zero, the skewness is approximately zero and the flatness is approximately equal to 3, representative of a normal distribution. At lower elevations the distribution of the fluctuations deviate substantially from a normal distribution, but are found to be well described by other standard theoretical probability distributions.
Original languageEnglish
Pages (from-to)192-230
Number of pages39
JournalJournal of Fluid Mechanics
Volume849
Early online date18 Jun 2018
DOIs
Publication statusPublished - 25 Aug 2018

Fingerprint

boundary layer flow
Boundary layer flow
Turbulence
turbulence
Statistics
statistics
flatness
Direct numerical simulation
Normal distribution
direct numerical simulation
normal density functions
wall flow
Higher order statistics
Wall flow
skewness
intermittency
turbulent flow
Probability distributions
Turbulent flow
low speed

Keywords

  • coastal engineering
  • surface gravity waves
  • turbulent boundary layers

Cite this

Turbulence statistics in smooth wall oscillatory boundary layer flow. / Van der A, Dominic A.; Scandura, Pietro; O'Donoghue, Thomas.

In: Journal of Fluid Mechanics, Vol. 849, 25.08.2018, p. 192-230.

Research output: Contribution to journalArticle

@article{35d7f6bb79f448e0b2d2b4c030fe3910,
title = "Turbulence statistics in smooth wall oscillatory boundary layer flow",
abstract = "Turbulence characteristics of an asymmetric oscillatory boundary layer flow are analysed through two-component laser-Doppler measurements carried out in a large oscillatory flow tunnel and direct numerical simulation (DNS). Five different Reynolds numbers, , in the range 846–2057 have been investigated experimentally, where with the maximum oscillatory velocity in the irrotational region, the Stokes length and the fluid kinematic viscosity. DNS has been carried out for the lowest three equal to 846, 1155 and 1475. Both experimental and numerical results show that the flow statistics increase during accelerating phases of the flow and especially at times of transition to turbulent flow. Once turbulence is fully developed, the near-wall statistics remain almost constant until the late half-cycle, with values close to those reported for steady wall-bounded flows. The higher-order statistics reach large values within a normalized wall distance of approximately at phases corresponding to the onset of low-speed streak breaking, because of the intermittency of the velocity fluctuations at these times. In particular, the flatness of the streamwise velocity fluctuations reaches values of the order of ten, while the flatness of the wall-normal velocity fluctuations reaches values of several hundreds. Far from the wall, at locations where the vertical gradient of the streamwise velocity is zero, the skewness is approximately zero and the flatness is approximately equal to 3, representative of a normal distribution. At lower elevations the distribution of the fluctuations deviate substantially from a normal distribution, but are found to be well described by other standard theoretical probability distributions.",
keywords = "coastal engineering, surface gravity waves, turbulent boundary layers",
author = "{Van der A}, {Dominic A.} and Pietro Scandura and Thomas O'Donoghue",
note = "This work has been carried out within the SINBAD project, funded through the UK’s Engineering and Physical Sciences Research Council (EPSRC grant EP/J00507X/1). PS acknowledges the funding from the University of Aberdeen to support his Honoray Research Fellowship and funding from the Ministero dell’Istruzione dell’Universit`a e della Ricerca through PRIN 2012 “Hydromorphodynamic and modeling of coastal processes for engineering purposes”. The authors acknowledge the support of the technical staff at the University of Aberdeen, especially Fluids Laboratory Technician Roy Gillanders. The experimental and numerical datasets presented in this paper are available on https://dx.doi.org/10.5281/zenodo.1095116.",
year = "2018",
month = "8",
day = "25",
doi = "10.1017/jfm.2018.403",
language = "English",
volume = "849",
pages = "192--230",
journal = "Journal of Fluid Mechanics",
issn = "0022-1120",
publisher = "Cambridge Univ. Press.",

}

TY - JOUR

T1 - Turbulence statistics in smooth wall oscillatory boundary layer flow

AU - Van der A, Dominic A.

AU - Scandura, Pietro

AU - O'Donoghue, Thomas

N1 - This work has been carried out within the SINBAD project, funded through the UK’s Engineering and Physical Sciences Research Council (EPSRC grant EP/J00507X/1). PS acknowledges the funding from the University of Aberdeen to support his Honoray Research Fellowship and funding from the Ministero dell’Istruzione dell’Universit`a e della Ricerca through PRIN 2012 “Hydromorphodynamic and modeling of coastal processes for engineering purposes”. The authors acknowledge the support of the technical staff at the University of Aberdeen, especially Fluids Laboratory Technician Roy Gillanders. The experimental and numerical datasets presented in this paper are available on https://dx.doi.org/10.5281/zenodo.1095116.

PY - 2018/8/25

Y1 - 2018/8/25

N2 - Turbulence characteristics of an asymmetric oscillatory boundary layer flow are analysed through two-component laser-Doppler measurements carried out in a large oscillatory flow tunnel and direct numerical simulation (DNS). Five different Reynolds numbers, , in the range 846–2057 have been investigated experimentally, where with the maximum oscillatory velocity in the irrotational region, the Stokes length and the fluid kinematic viscosity. DNS has been carried out for the lowest three equal to 846, 1155 and 1475. Both experimental and numerical results show that the flow statistics increase during accelerating phases of the flow and especially at times of transition to turbulent flow. Once turbulence is fully developed, the near-wall statistics remain almost constant until the late half-cycle, with values close to those reported for steady wall-bounded flows. The higher-order statistics reach large values within a normalized wall distance of approximately at phases corresponding to the onset of low-speed streak breaking, because of the intermittency of the velocity fluctuations at these times. In particular, the flatness of the streamwise velocity fluctuations reaches values of the order of ten, while the flatness of the wall-normal velocity fluctuations reaches values of several hundreds. Far from the wall, at locations where the vertical gradient of the streamwise velocity is zero, the skewness is approximately zero and the flatness is approximately equal to 3, representative of a normal distribution. At lower elevations the distribution of the fluctuations deviate substantially from a normal distribution, but are found to be well described by other standard theoretical probability distributions.

AB - Turbulence characteristics of an asymmetric oscillatory boundary layer flow are analysed through two-component laser-Doppler measurements carried out in a large oscillatory flow tunnel and direct numerical simulation (DNS). Five different Reynolds numbers, , in the range 846–2057 have been investigated experimentally, where with the maximum oscillatory velocity in the irrotational region, the Stokes length and the fluid kinematic viscosity. DNS has been carried out for the lowest three equal to 846, 1155 and 1475. Both experimental and numerical results show that the flow statistics increase during accelerating phases of the flow and especially at times of transition to turbulent flow. Once turbulence is fully developed, the near-wall statistics remain almost constant until the late half-cycle, with values close to those reported for steady wall-bounded flows. The higher-order statistics reach large values within a normalized wall distance of approximately at phases corresponding to the onset of low-speed streak breaking, because of the intermittency of the velocity fluctuations at these times. In particular, the flatness of the streamwise velocity fluctuations reaches values of the order of ten, while the flatness of the wall-normal velocity fluctuations reaches values of several hundreds. Far from the wall, at locations where the vertical gradient of the streamwise velocity is zero, the skewness is approximately zero and the flatness is approximately equal to 3, representative of a normal distribution. At lower elevations the distribution of the fluctuations deviate substantially from a normal distribution, but are found to be well described by other standard theoretical probability distributions.

KW - coastal engineering

KW - surface gravity waves

KW - turbulent boundary layers

U2 - 10.1017/jfm.2018.403

DO - 10.1017/jfm.2018.403

M3 - Article

VL - 849

SP - 192

EP - 230

JO - Journal of Fluid Mechanics

JF - Journal of Fluid Mechanics

SN - 0022-1120

ER -