Hysterical effects in flow structure behind a finite array of cylinders under gradually varying unsteady flow conditions

Eryilmaz Erdog; Oral Yagci; V. S.Ozgur Kirca

doi:10.1007/s40722-022-00229-y

Hysterical effects in flow structure behind a finite array of cylinders under gradually varying unsteady flow conditions

Eryilmaz Erdog, Oral Yagci^*, V. S.Ozgur Kirca

^*Corresponding author for this work

Department of Civil Engineering

Istanbul Technical University

Research output: Contribution to journal › Article › peer-review

1 Citation (Scopus)

Abstract

Recent investigations revealed that a group of cylinders offer more advantages than mono-pile when applied as a foundation for offshore wind turbines or pile-supported structures. In this context, the influence of gradually varying unsteady flow around a group of cylinder (Hexagonal arrays of circular cylinders, HACCs) was investigated by flume experiments. Reproducible gradually varying flow conditions were repeated in the flume for each point on the measurement grid distributed around the cylinder group. The dimensions of the recirculating flume, equipped with an electronically programmable discharge pump, were 30 m in length and 1 m in width. Spatio-temporal variations of the turbulence and mean flow quantities were obtained during the passage of the unsteady and steady flow. The experimental findings demonstrated that the velocity difference between contraction and wake regions is more significant during the falling stage of the unsteady flow than the rising stage for both arrangements of HACC. Besides, a hysterical counter-clockwise relationship between TKE and normalized streamwise velocity in the wake region of both cases of HACC was observed. Nevertheless, under steady flow conditions, while the regular array of HACC generates higher resistance compared to the unsteady case, the staggered array exhibited lower resistance.

Original language	English
Pages (from-to)	247-267
Number of pages	21
Journal	Journal of Ocean Engineering and Marine Energy
Volume	8
Issue number	3
DOIs	https://doi.org/10.1007/s40722-022-00229-y
Publication status	Published - Aug 2022

Bibliographical note

Publisher Copyright:
© 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Funding

The present study emanates from the Ph.D. thesis of the first author. The full set of data can directly be obtained from Ph.D. thesis which is currently in writing stage by Eryilmaz Erdog. The authors gratefully acknowledge the precise work and great efforts of technicians H. Yalçın and M. Uluçınar, who employ in Hydraulics Laboratory of Istanbul Technical University. The financial support from the Scientific Research Funding Program of Istanbul Technical University provided for the construction of the flume (ITU-BAP Program, MDK-2017-40708) is gratefully acknowledged. The present study emanates from the Ph.D. thesis of the first author. The full set of data can directly be obtained from Ph.D. thesis which is currently in writing stage by Eryilmaz Erdog. The authors gratefully acknowledge the precise work and great efforts of technicians H. Yalçın and M. Uluçınar, who employ in Hydraulics Laboratory of Istanbul Technical University. The financial support from the Scientific Research Funding Program of Istanbul Technical University provided for the construction of the flume (ITU-BAP Program, MDK-2017-40708) is gratefully acknowledged.

Funders	Funder number
Eryilmaz Erdog
Istanbul Teknik Üniversitesi	MDK-2017-40708

Keywords

Bleed flow
Drag
Foundation
Group of pile
Hysteresis
Pairs of vortices
Pier
Supporting pile
Unsteady flow
Vegetation–flow interaction
Wake region

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Cite this

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title = "Hysterical effects in flow structure behind a finite array of cylinders under gradually varying unsteady flow conditions",

abstract = "Recent investigations revealed that a group of cylinders offer more advantages than mono-pile when applied as a foundation for offshore wind turbines or pile-supported structures. In this context, the influence of gradually varying unsteady flow around a group of cylinder (Hexagonal arrays of circular cylinders, HACCs) was investigated by flume experiments. Reproducible gradually varying flow conditions were repeated in the flume for each point on the measurement grid distributed around the cylinder group. The dimensions of the recirculating flume, equipped with an electronically programmable discharge pump, were 30 m in length and 1 m in width. Spatio-temporal variations of the turbulence and mean flow quantities were obtained during the passage of the unsteady and steady flow. The experimental findings demonstrated that the velocity difference between contraction and wake regions is more significant during the falling stage of the unsteady flow than the rising stage for both arrangements of HACC. Besides, a hysterical counter-clockwise relationship between TKE and normalized streamwise velocity in the wake region of both cases of HACC was observed. Nevertheless, under steady flow conditions, while the regular array of HACC generates higher resistance compared to the unsteady case, the staggered array exhibited lower resistance.",

keywords = "Bleed flow, Drag, Foundation, Group of pile, Hysteresis, Pairs of vortices, Pier, Supporting pile, Unsteady flow, Vegetation–flow interaction, Wake region",

author = "Eryilmaz Erdog and Oral Yagci and Kirca, {V. S.Ozgur}",

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year = "2022",

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doi = "10.1007/s40722-022-00229-y",

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Y1 - 2022/8

N2 - Recent investigations revealed that a group of cylinders offer more advantages than mono-pile when applied as a foundation for offshore wind turbines or pile-supported structures. In this context, the influence of gradually varying unsteady flow around a group of cylinder (Hexagonal arrays of circular cylinders, HACCs) was investigated by flume experiments. Reproducible gradually varying flow conditions were repeated in the flume for each point on the measurement grid distributed around the cylinder group. The dimensions of the recirculating flume, equipped with an electronically programmable discharge pump, were 30 m in length and 1 m in width. Spatio-temporal variations of the turbulence and mean flow quantities were obtained during the passage of the unsteady and steady flow. The experimental findings demonstrated that the velocity difference between contraction and wake regions is more significant during the falling stage of the unsteady flow than the rising stage for both arrangements of HACC. Besides, a hysterical counter-clockwise relationship between TKE and normalized streamwise velocity in the wake region of both cases of HACC was observed. Nevertheless, under steady flow conditions, while the regular array of HACC generates higher resistance compared to the unsteady case, the staggered array exhibited lower resistance.

AB - Recent investigations revealed that a group of cylinders offer more advantages than mono-pile when applied as a foundation for offshore wind turbines or pile-supported structures. In this context, the influence of gradually varying unsteady flow around a group of cylinder (Hexagonal arrays of circular cylinders, HACCs) was investigated by flume experiments. Reproducible gradually varying flow conditions were repeated in the flume for each point on the measurement grid distributed around the cylinder group. The dimensions of the recirculating flume, equipped with an electronically programmable discharge pump, were 30 m in length and 1 m in width. Spatio-temporal variations of the turbulence and mean flow quantities were obtained during the passage of the unsteady and steady flow. The experimental findings demonstrated that the velocity difference between contraction and wake regions is more significant during the falling stage of the unsteady flow than the rising stage for both arrangements of HACC. Besides, a hysterical counter-clockwise relationship between TKE and normalized streamwise velocity in the wake region of both cases of HACC was observed. Nevertheless, under steady flow conditions, while the regular array of HACC generates higher resistance compared to the unsteady case, the staggered array exhibited lower resistance.

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KW - Group of pile

KW - Hysteresis

KW - Pairs of vortices

KW - Pier

KW - Supporting pile

KW - Unsteady flow

KW - Vegetation–flow interaction

KW - Wake region

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Hysterical effects in flow structure behind a finite array of cylinders under gradually varying unsteady flow conditions

Abstract

Bibliographical note

Funding

Keywords

UN SDGs

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