Generalized coutte flow of herschel-bulkley fluid through eccentric annulus-an approximate solution

Date

2006

Author

Seyidoğlu, Tijen

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Generalized Couette flow of a Herschel-Bulkley fluid in an eccentric annulus is analyzed by approximating the flow geometry as a slit of variable height. Besides an imposed pressure gradient, one of the plates is considered non-stationary to take into account the axial and/or angular motion of the inner pipe in an eccentric annulus system. Depending on the magnitude and the direction of the applied pressure gradient with respect to the plate velocity, three separate flow cases are studied in which the velocity reaches its maximum value either within the plug flow region or at the moving boundary. Velocity distributions are obtained for each case by solving the equations of continuity and motion. Volumetric flow rate expressions are obtained by integrating the velocity distribution over the cross-sectional area. At a given pressure gradient, the results indicate an increase in volumetric flow rate with an increase in eccentricity ratio. Criteria for each flow type is developed in terms of a dimensionless parameter ?, which takes into account the ratio of the imposed pressure gradient to the plate velocity. Volumetric flow rate expressions for Newtonian, Bingham and power-law fluids are obtained by considering the limiting values of the fluid index and yield stress. The validity of the equations are checked by considering the slit height to be a constant, i.e., flow between parallel plates. Surge/swab pressure calculations are carried out for Herschel-Bulkley, power-law and Bingham fluids and the results are expressed as a function of eccentricity ratio, radius ratio, fluid index and yield stress. The results indicate that when the fluid index and the eccentricity ratio are fixed, a slight increase in the radius ratio causes a tremendous increase in surge/swab pressure, especially for low values of fluid index. On the other hand, displacement of the inner pipe from a

Subject Keywords

Chemical Engineering Civil engineering.

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http://etd.lib.metu.edu.tr/upload/2/12607087/index.pdf
https://hdl.handle.net/11511/15726

Collections

Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

T. Seyidoğlu, “Generalized coutte flow of herschel-bulkley fluid through eccentric annulus-an approximate solution,” M.S. - Master of Science, Middle East Technical University, 2006.