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Laminar and turbulent boundary layer...

Afroz, Farhana.

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Laminar and turbulent boundary layer separation control of Mako shark skin.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Laminar and turbulent boundary layer separation control of Mako shark skin./
Author:	Afroz, Farhana.
Description:	162 p.
Notes:	Source: Dissertation Abstracts International, Volume: 75-08(E), Section: B.
Contained By:	Dissertation Abstracts International75-08B(E).
Subject:	Engineering, Aerospace. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3620048
ISBN:	9781303897290

Laminar and turbulent boundary layer separation control of Mako shark skin.
Afroz, Farhana.

Laminar and turbulent boundary layer separation control of Mako shark skin. - 162 p.

Source: Dissertation Abstracts International, Volume: 75-08(E), Section: B.

Thesis (Ph.D.)--The University of Alabama, 2014.

The Shortfin Mako shark (Isurus oxyrinchus) is one of the fastest swimmers in nature. They have an incredible turning agility and are estimated to achieve speeds as high as ten body lengths per second. Shark skin is known to contain flexible denticles or scales, capable of being actuated by the flow whereby a unique boundary layer control (BLC) method could reduce drag. It is hypothesized that shark scales bristle when the flow is reversed, and this bristling may serve to control flow separation by (1) inhibiting the localized flow reversal near the wall and (2) inducing mixing within the boundary layer by cavities formed between the scales that increases the momentum of the flow near the wall. To test this hypothesis, samples of Mako shark skin have been studied under various amounts of adverse pressure gradient (APG). These samples were collected from the flank region of a Shortfin Mako shark where the scales have the greatest potential for separation control due to the highest bristling angles. An easy technique for inducing boundary layer separation has been developed where an APG can be generated and varied using a rotating cylinder. Both the experimental and numerical studies showed that the amount of APG can be varied as a function of cylinder rotation speed or cylinder gap height for a wide range of Reynolds numbers. This method of generating an APG is used effectively for inducing both laminar and turbulent boundary layer separation over a flat plate. Laminar and turbulent boundary layer separation studies conducted over a smooth plate have been compared with the same setup repeated over shark skin. The time-averaged DPIV results showed that shark scale bristling controlled both laminar and turbulent boundary layer separation to a measurable extent. It shows that the shark scales cause an early transition to turbulence and reduce the degree of laminar separation. For turbulent separation, reverse flow near the wall and inside the boundary layer is hypothesized to bristle the shark scales thereby preventing the reverse flow from reaching higher magnitudes that leads to global flow separation.

ISBN: 9781303897290Subjects--Topical Terms:

1018395
Engineering, Aerospace.

Laminar and turbulent boundary layer separation control of Mako shark skin.
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020 $a 9781303897290
035 $a (MiAaPQ)AAI3620048
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100 1 $a Afroz, Farhana. $3 3169137
245 1 0 $a Laminar and turbulent boundary layer separation control of Mako shark skin.
300 $a 162 p.
500 $a Source: Dissertation Abstracts International, Volume: 75-08(E), Section: B.
500 $a Adviser: Amy W. Lang.
502 $a Thesis (Ph.D.)--The University of Alabama, 2014.
520 $a The Shortfin Mako shark (Isurus oxyrinchus) is one of the fastest swimmers in nature. They have an incredible turning agility and are estimated to achieve speeds as high as ten body lengths per second. Shark skin is known to contain flexible denticles or scales, capable of being actuated by the flow whereby a unique boundary layer control (BLC) method could reduce drag. It is hypothesized that shark scales bristle when the flow is reversed, and this bristling may serve to control flow separation by (1) inhibiting the localized flow reversal near the wall and (2) inducing mixing within the boundary layer by cavities formed between the scales that increases the momentum of the flow near the wall. To test this hypothesis, samples of Mako shark skin have been studied under various amounts of adverse pressure gradient (APG). These samples were collected from the flank region of a Shortfin Mako shark where the scales have the greatest potential for separation control due to the highest bristling angles. An easy technique for inducing boundary layer separation has been developed where an APG can be generated and varied using a rotating cylinder. Both the experimental and numerical studies showed that the amount of APG can be varied as a function of cylinder rotation speed or cylinder gap height for a wide range of Reynolds numbers. This method of generating an APG is used effectively for inducing both laminar and turbulent boundary layer separation over a flat plate. Laminar and turbulent boundary layer separation studies conducted over a smooth plate have been compared with the same setup repeated over shark skin. The time-averaged DPIV results showed that shark scale bristling controlled both laminar and turbulent boundary layer separation to a measurable extent. It shows that the shark scales cause an early transition to turbulence and reduce the degree of laminar separation. For turbulent separation, reverse flow near the wall and inside the boundary layer is hypothesized to bristle the shark scales thereby preventing the reverse flow from reaching higher magnitudes that leads to global flow separation.
590 $a School code: 0004.
650 4 $a Engineering, Aerospace. $3 1018395
650 4 $a Engineering, Mechanical. $3 783786
650 4 $a Engineering, General. $3 1020744
690 $a 0538
690 $a 0548
690 $a 0537
710 2 $a The University of Alabama. $b Aerospace Engineering. $3 3169138
773 0 $t Dissertation Abstracts International $g 75-08B(E).
790 $a 0004
791 $a Ph.D.
792 $a 2014
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3620048