Effects of wall roughness on turbulent junction flow characteristics

Effects of wall roughness on turbulent junction flow characteristics Global measurements of turbulent flows at wall–cylinder junctions are employed to quantify the effects of wall roughness on the behavior of the horseshoe vortex system (HVS). Two laboratory setups were considered: one with an impermeable smooth wall and a second characterized by a porous hydraulically rough bed. The measurements were obtained using planar particle image velocimetry. Time-averaged flow topology, turbulence statistics, and instantaneous fields associated with the streamwise and wall-normal velocity components are emphasized. Proper orthogonal decomposition (POD) is also applied on the velocity signals to probe into the characteristics of the energetic flow structures. For the Reynolds numbers studied here and the specific differences in the roughness geometry of the bed, a clear trend for the increase in flow incoherence due to the rough wall is documented. It is also demonstrated that, in the presence of roughness, vorticity and turbulence spread more evenly throughout the junction. On the other hand, qualitative and quantitative agreement between the smooth and rough bed tests is found in the structure of the downflow and the near-wall jet opposing the bulk flow. The efficiency of POD in analyzing turbulent junction flows is justified based on its results and metrics of modal energy distribution. POD verified in an objective way the role of integral components of the HVS dynamics such as the vortices comprising the system and their interplay with the wall. The decomposition furnishes new evidence about energetic structures that were not captured with the other data analysis methodologies. It also confirms the aperiodic behavior of the HVS for the investigated Reynolds numbers. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Effects of wall roughness on turbulent junction flow characteristics

Loading next page...
 
/lp/springer_journal/effects-of-wall-roughness-on-turbulent-junction-flow-characteristics-4Z2ewm3jZ0
Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2015 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-015-2098-0
Publisher site
See Article on Publisher Site

Abstract

Global measurements of turbulent flows at wall–cylinder junctions are employed to quantify the effects of wall roughness on the behavior of the horseshoe vortex system (HVS). Two laboratory setups were considered: one with an impermeable smooth wall and a second characterized by a porous hydraulically rough bed. The measurements were obtained using planar particle image velocimetry. Time-averaged flow topology, turbulence statistics, and instantaneous fields associated with the streamwise and wall-normal velocity components are emphasized. Proper orthogonal decomposition (POD) is also applied on the velocity signals to probe into the characteristics of the energetic flow structures. For the Reynolds numbers studied here and the specific differences in the roughness geometry of the bed, a clear trend for the increase in flow incoherence due to the rough wall is documented. It is also demonstrated that, in the presence of roughness, vorticity and turbulence spread more evenly throughout the junction. On the other hand, qualitative and quantitative agreement between the smooth and rough bed tests is found in the structure of the downflow and the near-wall jet opposing the bulk flow. The efficiency of POD in analyzing turbulent junction flows is justified based on its results and metrics of modal energy distribution. POD verified in an objective way the role of integral components of the HVS dynamics such as the vortices comprising the system and their interplay with the wall. The decomposition furnishes new evidence about energetic structures that were not captured with the other data analysis methodologies. It also confirms the aperiodic behavior of the HVS for the investigated Reynolds numbers.

Journal

Experiments in FluidsSpringer Journals

Published: Dec 26, 2015

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off