Computational studies of flow in Couette Rheometer and particle interaction in nonNewtonian fluids
(2016) Abstract
 This work aims to study the flow of nonNewtonian fluids and has two main goals. First, the powerlaw and Herschel Bulkley fluids are studied in a Couette rheometer. Second, the static and dynamic interaction of dual particles in powerlaw fluid are investigated.
For the first goal, Computational Fluid Dynamics (CFD) is employed to understand the flow behavior of powerlaw fluid in the Couette rheometer, and to find more accurate predictorcorrector methods to enhance the accuracy of fluid properties estimation by the measurement. Unlike the previous numericalbased method, the current correction factors take into account the effect of wide gap into a single coefficient besides the effect of the end parts. This novel method, including... (More)  This work aims to study the flow of nonNewtonian fluids and has two main goals. First, the powerlaw and Herschel Bulkley fluids are studied in a Couette rheometer. Second, the static and dynamic interaction of dual particles in powerlaw fluid are investigated.
For the first goal, Computational Fluid Dynamics (CFD) is employed to understand the flow behavior of powerlaw fluid in the Couette rheometer, and to find more accurate predictorcorrector methods to enhance the accuracy of fluid properties estimation by the measurement. Unlike the previous numericalbased method, the current correction factors take into account the effect of wide gap into a single coefficient besides the effect of the end parts. This novel method, including the effect of the wide gap, can enhance the accuracy up to 16% depending on the fluid behavior and the gap distance. For Herschel Bulkley fluid, Finite Element Method (FEM) is also employed in addition to CFD. It is shown that compared to the analytical solution, the presented method can enhance the accuracy of the yield stress value estimation about 11% and the consistency index about 23%. In this section, the effect of the plug flow on the inverse problem solution of the Couette flow has also been evaluated. By the Couette inverse problem solution and the superposition assumption of the fluid and solid part of the Herschel Bulkley model, it is shown that except Bingham fluid, the superposition assumption introduces significant error to the calculations especially for powerlaw index less than 0.7 and ratio of yield stress to consistency index less than 50. For shear thickening fluid, one should takes into account the discrepancy introduced by the assumption as well. The discrepancy introduced is in the range of 0 – 6%.
The second goal is to study both static and dynamic interaction of the particles in nonNewtonian media for spherical and cubical particle shapes, respectively. To study the static interaction of the particles, the variation of drag and lift coefficients of two fixed spherical particles for various dual sphere configurations in a powerlaw fluid has been investigated. The results show that the influence of the shear thinning cannot be overlooked even at the higher Reynolds number. The drag and lift coefficients are compared in different states, and the wake strength is assessed in the tandem cases. Repulsion and attraction forces are observed when the direction of the lift forces is changed due to the high and low pressure regions between the spheres. Regarding the dynamic interaction of cubical particles, the results indicate that there is a horizontal separation distance in which the particles behaves close to that of a singular particle. Moreover, increasing the vertical distance would have the result in decrease of the effect of the horizontal separation distance. Increasing the vertical separation distance greater than 3.0D makes the interaction more complex. Kissing, drafting and tumbling are also observed in these simulations. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/a278b123f8dc41789e044eefd097b4b1
 author
 Hamedi, Naser ^{LU}
 opponent

 Professor John Tsamopoulos, University of Patras, Greece
 organization
 publishing date
 2016
 type
 Thesis
 publication status
 published
 keywords
 NonNewtonian fluids, Correction factor, Fluid properties, Couette Rheometer, Particle interaction, Sedimentation, Computational Fluid dynamics, Plug flow, Herschel Bulkley, Powerlaw fluid, Immeresed boundary method
 pages
 80 pages
 publisher
 Lund University (MediaTryck)
 defense location
 Lecture hall M:B, Mbuilding, Ole Römers väg 1, Lund University, Faculty of Engineering
 defense date
 20160913 10:15
 ISBN
 9789176239308
 language
 English
 LU publication?
 yes
 id
 a278b123f8dc41789e044eefd097b4b1
 date added to LUP
 20160816 15:13:26
 date last changed
 20160817 08:32:08
@phdthesis{a278b123f8dc41789e044eefd097b4b1, abstract = {This work aims to study the flow of nonNewtonian fluids and has two main goals. First, the powerlaw and Herschel Bulkley fluids are studied in a Couette rheometer. Second, the static and dynamic interaction of dual particles in powerlaw fluid are investigated.<br/>For the first goal, Computational Fluid Dynamics (CFD) is employed to understand the flow behavior of powerlaw fluid in the Couette rheometer, and to find more accurate predictorcorrector methods to enhance the accuracy of fluid properties estimation by the measurement. Unlike the previous numericalbased method, the current correction factors take into account the effect of wide gap into a single coefficient besides the effect of the end parts. This novel method, including the effect of the wide gap, can enhance the accuracy up to 16% depending on the fluid behavior and the gap distance. For Herschel Bulkley fluid, Finite Element Method (FEM) is also employed in addition to CFD. It is shown that compared to the analytical solution, the presented method can enhance the accuracy of the yield stress value estimation about 11% and the consistency index about 23%. In this section, the effect of the plug flow on the inverse problem solution of the Couette flow has also been evaluated. By the Couette inverse problem solution and the superposition assumption of the fluid and solid part of the Herschel Bulkley model, it is shown that except Bingham fluid, the superposition assumption introduces significant error to the calculations especially for powerlaw index less than 0.7 and ratio of yield stress to consistency index less than 50. For shear thickening fluid, one should takes into account the discrepancy introduced by the assumption as well. The discrepancy introduced is in the range of 0 – 6%.<br/>The second goal is to study both static and dynamic interaction of the particles in nonNewtonian media for spherical and cubical particle shapes, respectively. To study the static interaction of the particles, the variation of drag and lift coefficients of two fixed spherical particles for various dual sphere configurations in a powerlaw fluid has been investigated. The results show that the influence of the shear thinning cannot be overlooked even at the higher Reynolds number. The drag and lift coefficients are compared in different states, and the wake strength is assessed in the tandem cases. Repulsion and attraction forces are observed when the direction of the lift forces is changed due to the high and low pressure regions between the spheres. Regarding the dynamic interaction of cubical particles, the results indicate that there is a horizontal separation distance in which the particles behaves close to that of a singular particle. Moreover, increasing the vertical distance would have the result in decrease of the effect of the horizontal separation distance. Increasing the vertical separation distance greater than 3.0D makes the interaction more complex. Kissing, drafting and tumbling are also observed in these simulations.}, author = {Hamedi, Naser}, isbn = {9789176239308}, keyword = {NonNewtonian fluids,Correction factor,Fluid properties,Couette Rheometer,Particle interaction,Sedimentation,Computational Fluid dynamics,Plug flow,Herschel Bulkley,Powerlaw fluid,Immeresed boundary method}, language = {eng}, pages = {80}, publisher = {Lund University (MediaTryck)}, school = {Lund University}, title = {Computational studies of flow in Couette Rheometer and particle interaction in nonNewtonian fluids}, year = {2016}, }