Secondary flows in statistically unstable turbulent boundary layers with spanwise heterogeneous roughness

This paper examines changes in the mean velocity profiles of turbulent boundary layers subjected to system rotation. Analysis of the data from several studies conducted in the large rotating wind tunnel at the University of Melbourne shows the existence of a universal linear correction to the velocity profile in the logarithmic region. The appropriate parameters relevant to rotation are derived and correlations are found between the parameters. Flows with adverse pressure gradients, zero pressure gradients and secondary flows are examined and all appear to exhibit the universal linear correction, suggesting that it is robust.

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The instantaneous structure of secondary flows in turbulent boundary layers

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.955 ◽

2019 ◽

Vol 862 ◽

pp. 845-870 ◽

Cited By ~ 10

Author(s):

C. Vanderwel ◽

A. Stroh ◽

J. Kriegseis ◽

B. Frohnapfel ◽

B. Ganapathisubramani

Keyword(s):

Boundary Layers ◽

Wall Stress ◽

Flow Patterns ◽

Turbulent Boundary Layers ◽

Secondary Flows ◽

Homogeneous Distribution ◽

Mean Flow ◽

Number Range ◽

Instantaneous Flow ◽

Near Wall

Secondary flows can develop in turbulent boundary layers that grow over surfaces with spanwise inhomogeneities. In this article, we demonstrate the formation of secondary flows in both experimental and numerical tests and dissect the instantaneous structure and topology of these secondary motions. We show that the formation of secondary flows is not very sensitive to the Reynolds number range investigated, and direct numerical simulations and experiments produce similar results in the mean flow as well as the dispersive and turbulent stress distributions. The numerical methods capture time-resolved features of the instantaneous flow and provide insight into the near-wall flow structures, that were previously obscured in the experimental measurements. Proper orthogonal decomposition was shown to capture the essence of the secondary flows in relatively few modes and to be useful as a filter to analyse the instantaneous flow patterns. The secondary flows are found to create extended regions of high Reynolds stress away from the wall that comprise predominantly sweeps similar to what one would expect to see near the wall and which are comparable in magnitude to the near-wall stress. Analysis of the instantaneous flow patterns reveals that the secondary flows are the result of a non-homogeneous distribution of mid-size vortices.

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Effects of heterogeneous surface geometry on secondary flows in turbulent boundary layers

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.1014 ◽

2020 ◽

Vol 886 ◽

Cited By ~ 3

Author(s):

T. Medjnoun ◽

C. Vanderwel ◽

B. Ganapathisubramani

Keyword(s):

Boundary Layers ◽

Turbulent Boundary Layers ◽

Secondary Flows ◽

Heterogeneous Surface ◽

Surface Geometry ◽

Image Position

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Effects of spanwise spacing on large-scale secondary flows in rough-wall turbulent boundary layers

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.292 ◽

2015 ◽

Vol 774 ◽

Cited By ~ 55

Author(s):

Christina Vanderwel ◽

Bharathram Ganapathisubramani

Keyword(s):

Boundary Layer ◽

Layer Thickness ◽

Boundary Layers ◽

Boundary Layer Thickness ◽

Large Scale ◽

Turbulent Boundary Layers ◽

Surface Flow ◽

Secondary Flows ◽

Flow Conditions ◽

Roughness Elements

Large-scale secondary flows can sometimes appear in turbulent boundary layers formed over rough surfaces, creating low- and high-momentum pathways along the surface (Barros & Christensen, J. Fluid Mech., vol. 748, 2014, R1). We investigate experimentally the dependence of these secondary flows on surface/flow conditions by measuring the flows over streamwise strips of roughness with systematically varied spanwise spacing. We find that the large-scale secondary flows are accentuated when the spacing of the roughness elements is roughly proportional to the boundary layer thickness ${\it\delta}$, and do not appear for cases with finer spacing. Cases with coarser spacing also generate ${\it\delta}$-scale secondary flows with tertiary flows in the spaces in between. These results show that the ratio of the spanwise length scale of roughness heterogeneity to the boundary layer thickness is a critical parameter for the occurrence of these secondary motions in turbulent boundary layers over rough walls.

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Secondary flows and developing, turbulent boundary layers in a rotating duct

Journal of Fluid Mechanics ◽

10.1017/s0022112098002584 ◽

1998 ◽

Vol 373 ◽

pp. 1-32 ◽

Cited By ~ 12

Author(s):

I. MACFARLANE ◽

P. N. JOUBERT ◽

T. B. NICKELS

Keyword(s):

Aspect Ratio ◽

Secondary Flow ◽

Boundary Layers ◽

Suction Side ◽

Turbulent Boundary Layers ◽

Secondary Flows ◽

Turbulent Shear ◽

Mean Flow ◽

Flow Strength ◽

Aspect Ratios

The work presented in this paper represents an experimental investigation into secondary flows, turbulent boundary layers and the interaction of the two as they develop in a zero-pressure-gradient rotating flow field. A duct of intermediate aspect ratio was used to examine secondary flows and determine when they begin to govern the boundary layer development. The aspect ratio (A) was defined as duct height/width at the upstream end of the working section. Measurements were taken at three aspect ratios: A=1, 2 and 4.A qualitative indication of secondary flow strength was established with mean-cross-stream-plane velocity measurements. A first-order analysis of the secondary flow is presented which provides a reasonable estimation of their strength. Mid-span mean-flow, turbulence and spectra profiles were measured on the duct walls parallel to the axis of rotation. Results are generally presented for A=2 and 1. For A=4 and 2 there were minor effects of secondary flows observed on the mid-span mean flow parameters. The turbulent shear measurements showed some secondary flow effect for A=2. All turbulence and mean-flow quantities were strongly affected by secondary flows for A=1. Spectra results presented for A=2 showed most variation at the low-to-mid wavenumber end. Spectra results for A=1 showed a bodily shift of the whole spectrum towards low wavenumber on the pressure side and high wavenumber on the suction side.

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Three-dimensional boundary layers: a report on Euromech 2

Journal of Fluid Mechanics ◽

10.1017/s0022112067000394 ◽

1967 ◽

Vol 27 (2) ◽

pp. 369-380 ◽

Cited By ~ 6

Author(s):

J. H. Horlock ◽

J. F. Norbury ◽

J. C. Cooke

Keyword(s):

Boundary Layers ◽

Three Dimensional ◽

Turbulent Boundary Layers ◽

Secondary Flows ◽

List Type ◽

Delta Wings ◽

Laminar Boundary Layers ◽

Dimensional Boundary ◽

The Subject ◽

Introductory Review

The second European Mechanics Colloquium, on the subject of three-dimensional boundary layers, was held at Liverpool University from 4 to 7 January 1966 and was attended by thirty-eight people closely associated with current work in this field.The meeting was opened by an introductory review by J. C. Cooke, who successfully sought to provoke discussion by emphasizing areas of apparent agreement and disagreement. The discussions which followed were based on a series of contributions by participants in the Colloquium, and covered the following topics:Laminar boundary layers.Three-dimensional perturbations of two-dimensional turbulent boundary layers.Corner and secondary flows.Boundary layers associated with flow past obstacles.Flow over delta wings.Separation.Flow over rotating surfaces.Heat and mass transfer.Miscellaneous topics.In all these cases, the emphasis was on the three-dimensional nature of the flow, and in this report the discussions are summarized under these headings.

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