國立高雄大學圖資館 |

Language: English

Back

Turbulent drag reduction using rigid...

Paschkewitz, John Steven.

Turbulent drag reduction using rigid microfibers.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Turbulent drag reduction using rigid microfibers.
Author:	Paschkewitz, John Steven.
Description:	198 p.
Notes:	Adviser: Eric S. G. Shaqfeh.
Notes:	Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5882.
Contained By:	Dissertation Abstracts International65-11B.
Subject:	Engineering, Chemical.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3153074
ISBN:	9780496135202

Turbulent drag reduction using rigid microfibers.
Paschkewitz, John Steven.

Turbulent drag reduction using rigid microfibers. - 198 p.

Adviser: Eric S. G. Shaqfeh.

Thesis (Ph.D.)--Stanford University, 2005.

Simulations of polymer-fiber mixtures in the turbulent channel flow, motivated by observations of synergistic behavior in the literature, were performed. A synergy effect was only obtained in a small computational domain in which the turbulence structure is substantially modified. Lastly, drag reduction using a rigid rod-like polymer was experimentally and numerically investigated in a zero pressure gradient turbulent boundary layer. Using particle image velocimetry, drag reductions of up to 15% were observed using injection of the polysaccharide scleroglucan. The turbulence statistics obtained using DNS compare favorably to the experimental results, with differences due to the homogeneous concentration distribution assumed in the DNS.

ISBN: 9780496135202Subjects--Topical Terms:

226989
Engineering, Chemical.

Turbulent drag reduction using rigid microfibers.
LDR:03376nmm _2200289 _450 001 170579
005 20061228142150.5
008 090528s2005 eng d
020 $a 9780496135202
035 $a 00242609
040 $a UnM $c UnM
100 0 $a Paschkewitz, John Steven. $3 244606
245 1 0 $a Turbulent drag reduction using rigid microfibers.
300 $a 198 p.
500 $a Adviser: Eric S. G. Shaqfeh.
500 $a Source: Dissertation Abstracts International, Volume: 65-11, Section: B, page: 5882.
502 $a Thesis (Ph.D.)--Stanford University, 2005.
520 # $a Simulations of polymer-fiber mixtures in the turbulent channel flow, motivated by observations of synergistic behavior in the literature, were performed. A synergy effect was only obtained in a small computational domain in which the turbulence structure is substantially modified. Lastly, drag reduction using a rigid rod-like polymer was experimentally and numerically investigated in a zero pressure gradient turbulent boundary layer. Using particle image velocimetry, drag reductions of up to 15% were observed using injection of the polysaccharide scleroglucan. The turbulence statistics obtained using DNS compare favorably to the experimental results, with differences due to the homogeneous concentration distribution assumed in the DNS.
520 # $a Using DNS of a fiber drag-reduced turbulent channel flow, the effect of fiber rheology and the drag reduction mechanism are determined. Drag reductions of up to 26% are obtained, with semi-dilute, non-Brownian fibers being most effective. This result suggests that additive elasticity is not necessary for drag reduction. Fiber stresses are correlated to inter-vortex, biaxial extensional flow regions, with the spatial gradients of these stresses generating opposition forces that destroy nearby vortices. The cross-flow plane stress components are shown to be responsible for the drag reduction effect, with the largest contribution from small fluctuations in the x-z plane shear stress. The dynamics of stress generation are investigated using conditional statistics of fiber stress and orientation along Lagrangian pathlines in the drag-reduced flow. Fibers are shown to align in the cross-flow plane, generate stress and realign in the flow direction in a process taking approximately 4 strain units, defined using the strain rate along the fiber. The stress fluctuations end because nearby vortices are weakened or destroyed and not because of relative motion of the vortices and fibers.
520 # $a Using a combination of direct numerical simulation (DNS) and experiment, the mechanism by which rigid fibers cause turbulent drag reduction has been investigated. The fibers are assumed to have a length smaller than the scale of the spatial variations of the velocity field and negligible inertia; these "microfibers" include rigid biopolymers and colloids. Fiber extra stresses are modeled using a constitutive equation related to the moments of the fiber orientation.
590 $a School code: 0212.
650 # 0 $a Engineering, Chemical. $3 226989
650 # 0 $a Engineering, Mechanical. $3 212470
690 $a 0542
690 $a 0548
710 0 # $a Stanford University. $3 212607
773 0 # $g 65-11B. $t Dissertation Abstracts International
790 $a 0212
790 1 0 $a Shaqfeh, Eric S. G., $e advisor
791 $a Ph.D.
792 $a 2005
856 4 0 $u http://libsw.nuk.edu.tw:81/login?url=http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3153074 $z http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3153074