Viscoelastic Fluid Flow Past a Submerged Spheroidal Body (Birefringence, Free Energy)
Dairanieh, Issam Salah
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https://hdl.handle.net/2142/69742
Description
Title
Viscoelastic Fluid Flow Past a Submerged Spheroidal Body (Birefringence, Free Energy)
Author(s)
Dairanieh, Issam Salah
Issue Date
1984
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Abstract
A stable and time-efficient numerical algorithm has been developed to study the problem of homogeneous axisymmetric flow of a third order fluid past a spheriodal body. The numerical solution was shown to agree well with existing analytical solutions for several limiting cases (such as flow past a sphere), and was used to investigate the effects of the (a) body shape, (b) free stream conditions, and (c) fluid elasticity on the local velocity and stress fields. The results of this study indicate that while a submerged spheroid gave rise to strong and highly localized stress fields, an immersed sphere created a stress field of moderate strength extending over larger distances. Also, it was found that the different free stream velocity fields, which included uniform flow, simple extensional flow and converging flow, resulted in different stress fields the strongest of which was produced by the extensional flow. Finally, it was found that the elasticity of the fluid had a profound effect on the local stresses. In some cases, the fore-aft symmetry of the stress field was lost, in others circulatory flow regions were produced downstream, and in all cases the magnitude of the stress tensor was increased as a result of increasing the fluid elasticity.
The computed flow kinematics were further used to calculate the expected molecular orientation and flow birefringence of the macromolecules. A derivation was also made of the flow birefringence to verify that the commonly used form of the stress-optical law is not valid for solutions of rigid chains. In addition, the free energy change due to flow was computed and the relationship between the free energy and stress fields and their possible bearing on the flow-induced phase separation of polymers were considered.
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