TJ296 : An Analytical Study on Motion and Shape of Creeping Viscoelastic Drops Falling through Viscoelastic Media
Thesis > Central Library of Shahrood University > Mechanical Engineering > MSc > 2014
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Abstarct: Investigation on two phase flow problem and particularly motion of droplets descending in
another media is of great importance in medical fields (particularly production of penicillin),
sedimentation reservoirs, water treatment industries (in sedimentation process of solids in
water), heat exchangers and other problems in industry.
In the present study, an analytical solution baxsed on the perturbation method is obtained to
simulate the creeping flow and motion of a viscoelastic drop descending in another
immiscible viscoelastic quiescent media. In different industrial application any of these
media (interior or exterior fluids) can show non-Newtonian behaviors. For the sake of this
reason a rigorous investigation on the scenario in which both fluids are non-Newtonian is
carried out.
The quasi-linear and non-linear Oldroyd-B and Giesekus constitutive equations are
implemented for both interior and exterior phases due to theirs high suitability in simulation
of polymeric solutions behaviors. The perturbation parameters are considered to be Deborah
numbers defined baxsed on the corresponding relaxation times of drop and exterior fluids and
capillary number to linearize the governing equations. To check the accuracy of presented
solution an experimental part is also included to the current version of study. In the
experimental part a solution of Polyacrylamide in water/glycerin is implemented as the
interior viscoelastic phase. In previous studies Xantham gum were used in most of works that
dues to its rigid molecular structure it was not to be simulated perfectly using the presented
simple constitutive equations. Silicon oil is used as the exterior media which is a water
repellence fluid. Also due to its high viscosity, it is a great choice in creep simulation
scenario. In contrast to the generally spherical shape of Newtonian drop creeping in viscose
media, it is shown that the effect of elasticity in this scenario can even feature prolate and
oblate shapes. The results have shown suitable agreements with previously reported
experimental results.
The motion of the droplet in surrounding media is considered to be creeping. Effects of
different parameters including Deborah numbers, elasto-capillary number, viscosity ratios of
drop and exterior media and, viscosity ratio between the drop and external flows are
rigorously investigated on the shape, motion, stream function and drag force of drop falling
into quiescent media.
Keywords:
#Viscoelastic drops #Viscoelastic media #Creeping motion #Oldroyd-B model #Deborah number #Elasto-capillary number #Perturbation method.
Keeping place: Central Library of Shahrood University
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Keeping place: Central Library of Shahrood University
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