Flow characteristics and scaling past highly porous wall-mounted fences
File(s)
Accepted version
Author(s)
Rodriguez-Lopez, E
Bruce, PJK
Buxton, ORH
Type
Journal Article
Abstract
An extensive characterization of the flow past wall-mounted highly porous fences based on single-
and multi-scale geometries has been performed using hot-wire anemometry in a low-speed wind
tunnel. Whilst drag properties (estimated from the time-averaged momentum equation) seem to be
mostly dependent on the grids’ blockage ratio; wakes of different size and orientation bars seem to
generate distinct behaviours regarding turbulence properties. Far from the near-grid region, the flow
is dominated by the presence of two well-differentiated layers: one close to the wall dominated by
the near-wall behaviour and another one corresponding to the grid’s wake and shear layer, originating
from between this and the freestream. It is proposed that the effective thickness of the wall layer can
be inferred from the wall-normal profile of root-mean-square streamwise velocity or, alternatively,
from the wall-normal profile of streamwise velocity correlation. Using these definitions of wall-layer
thickness enables us to collapse different trends of the turbulence behaviour inside this layer. In
particular, the root-mean-square level of the wall shear stress fluctuations, longitudinal integral length
scale, and spanwise turbulent structure is shown to display a satisfactory scaling with this thickness
rather than with the whole thickness of the grid’s wake. Moreover, it is shown that certain grids
destroy the spanwise arrangement of large turbulence structures in the logarithmic region, which are
then re-formed after a particular streamwise extent. It is finally shown that for fences subject to a
boundary layer of thickness comparable to their height, the effective thickness of the wall layer scales
with the incoming boundary layer thickness. Analogously, it is hypothesized that the growth rate of
the internal layer is also partly dependent on the incoming boundary layer thickness.
and multi-scale geometries has been performed using hot-wire anemometry in a low-speed wind
tunnel. Whilst drag properties (estimated from the time-averaged momentum equation) seem to be
mostly dependent on the grids’ blockage ratio; wakes of different size and orientation bars seem to
generate distinct behaviours regarding turbulence properties. Far from the near-grid region, the flow
is dominated by the presence of two well-differentiated layers: one close to the wall dominated by
the near-wall behaviour and another one corresponding to the grid’s wake and shear layer, originating
from between this and the freestream. It is proposed that the effective thickness of the wall layer can
be inferred from the wall-normal profile of root-mean-square streamwise velocity or, alternatively,
from the wall-normal profile of streamwise velocity correlation. Using these definitions of wall-layer
thickness enables us to collapse different trends of the turbulence behaviour inside this layer. In
particular, the root-mean-square level of the wall shear stress fluctuations, longitudinal integral length
scale, and spanwise turbulent structure is shown to display a satisfactory scaling with this thickness
rather than with the whole thickness of the grid’s wake. Moreover, it is shown that certain grids
destroy the spanwise arrangement of large turbulence structures in the logarithmic region, which are
then re-formed after a particular streamwise extent. It is finally shown that for fences subject to a
boundary layer of thickness comparable to their height, the effective thickness of the wall layer scales
with the incoming boundary layer thickness. Analogously, it is hypothesized that the growth rate of
the internal layer is also partly dependent on the incoming boundary layer thickness.
Date Issued
2017-07-26
Date Acceptance
2017-07-05
Citation
Physics of Fluids, 2017, 29 (7)
ISSN
1070-6631
Publisher
AIP Publishing
Journal / Book Title
Physics of Fluids
Volume
29
Issue
7
Copyright Statement
© 2017 The Authors. Published by
AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Fluids and may be found at http://aip.scitation.org/doi/10.1063/1.4995307
AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Fluids and may be found at http://aip.scitation.org/doi/10.1063/1.4995307
Sponsor
Commission of the European Communities
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000406765200030&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Grant Number
FP7 - 317269
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
TURBULENT-BOUNDARY-LAYERS
MODERATE REYNOLDS-NUMBERS
SHEAR-STRESS
HOT-WIRE
SURFACE-ROUGHNESS
VELOCITY PROFILE
WIND-TUNNEL
STEP CHANGE
FORM DRAG
REGION
Publication Status
Published
Article Number
ARTN 075106