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The effects of gravity modulation on...

University of California, Santa Barbara., Mechanical Engineering.

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The effects of gravity modulation on fluid mixing.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	The effects of gravity modulation on fluid mixing./
Author:	Siddavaram, Vikram K.
Description:	167 p.
Notes:	Adviser: George M. Homsy.
Contained By:	Dissertation Abstracts International68-10B.
Subject:	Engineering, Mechanical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3283680
ISBN:	9780549268789

The effects of gravity modulation on fluid mixing.
Siddavaram, Vikram K.

The effects of gravity modulation on fluid mixing. - 167 p.

Adviser: George M. Homsy.

Thesis (Ph.D.)--University of California, Santa Barbara, 2007.

We numerically study the effects of zero-mean, time-dependent gravity modulation on the mixing characteristics of two interdiffusing miscible fluids initially separated by a thin vertical diffusion layer. For harmonic vertical modulation in 2D with frequency o, the evolution of the interface between the fluids is governed by the Grashof number, Gr = Drr gl3nn 2 , based on the viscous length scale, lnu = nw , the Schmidt number, Sc = nD , the phase angle of the harmonic modulation, &phis;, and other geometric parameters. When &phis; = 0, pi, we observe four different flow regimes with increasing Gr: neutral oscillations at the forcing frequency; successive folds which propagate diffusively; localized shear instabilities; and both shear and convective instabilities leading to rapid mixing. When &phis; ≠ 0 or pi, the flow is similar to a modulated lock exchange flow.

ISBN: 9780549268789Subjects--Topical Terms:

783786
Engineering, Mechanical.

The effects of gravity modulation on fluid mixing.
LDR:03455nam 2200349 a 45 001 852505
005 20100630
008 100630s2007 ||||||||||||||||| ||eng d
020 $a 9780549268789
035 $a (UMI)AAI3283680
035 $a AAI3283680
040 $a UMI $c UMI
100 1 $a Siddavaram, Vikram K. $3 1018401
245 1 4 $a The effects of gravity modulation on fluid mixing.
300 $a 167 p.
500 $a Adviser: George M. Homsy.
500 $a Source: Dissertation Abstracts International, Volume: 68-10, Section: B, page: 6923.
502 $a Thesis (Ph.D.)--University of California, Santa Barbara, 2007.
520 $a We numerically study the effects of zero-mean, time-dependent gravity modulation on the mixing characteristics of two interdiffusing miscible fluids initially separated by a thin vertical diffusion layer. For harmonic vertical modulation in 2D with frequency o, the evolution of the interface between the fluids is governed by the Grashof number, Gr = Drr gl3nn 2 , based on the viscous length scale, lnu = nw , the Schmidt number, Sc = nD , the phase angle of the harmonic modulation, &phis;, and other geometric parameters. When &phis; = 0, pi, we observe four different flow regimes with increasing Gr: neutral oscillations at the forcing frequency; successive folds which propagate diffusively; localized shear instabilities; and both shear and convective instabilities leading to rapid mixing. When &phis; ≠ 0 or pi, the flow is similar to a modulated lock exchange flow.
520 $a We also study the effects of zero-mean stochastic vertical gravity modulation which is normally distributed and characterized by an exponentially damped cosine auto-correlation function, i.e. &lang;g( t) · g(t + tau)&rang;/&lang; g2(t)&rang; = e -lambdataucos(otau). We observe the propagation of gravity currents, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, even for extremely small Gr. Narrow-band modulations lead to the largest mixed volumes followed by harmonic modulations and then broad-band modulations. This non-monotonicity is explained on the basis of the competition between the effects of excitation of lower frequencies and the effects of the reduction in the energy content at the dominant frequency.
520 $a For harmonic horizontal modulation, we observe a critical Gr for the occurrence of Rayleigh-Taylor instability. As Gr is increased, we observe that the flow-field becomes chaotic through a sequence of period-doubling bifurcations with a Feigenbaum-type scenario. Stochastic modulation leads to Rayleigh-Taylor instabilities at smaller equivalent Gr than harmonic modulation.
520 $a We study the effects of three dimensionality, which is generated by introducing a small streamwise vorticity perturbation to the 2D flow. For perturbed flows, increased pairing of the spanwise rollers due to counter-rotating streamwise vortices results in larger rollers which in turn enhance mixing. We find that vortex stretching is the mechanism for the increase in streamwise vorticity.
590 $a School code: 0035.
650 4 $a Engineering, Mechanical. $3 783786
650 4 $a Physics, Fluid and Plasma. $3 1018402
690 $a 0548
690 $a 0759
710 2 $a University of California, Santa Barbara. $b Mechanical Engineering. $3 1018391
773 0 $t Dissertation Abstracts International $g 68-10B.
790 $a 0035
790 1 0 $a Ceniceros, Hector $e committee member
790 1 0 $a Homsy, George M., $e advisor
790 1 0 $a Meiburg, Eckart $e committee member
790 1 0 $a Moehlis, Jeff $e committee member
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3283680