Soutenance de thèse : Hafiz Muhammad AHMAD

Experimental study of viscoelastic fluid flow in a rectangular channel: measurment of seconday flows

Doctorant : Hafiz Muhammad AHMAD

Laboratoire INSA : CETHIL

Ecole doctorale : ED162 : Mécanique, Energétique, Génie Civil, Acoustique de Lyon

During laminar flow of non-Newtonian viscoelastic fluids through asymmetric closed channels, transversal recirculation occurs at a plane normal to the main flow direction. Tthis is called secondary flow (VSF). These secondary flows, cause the reduction in mass flux, but enhances the heat transfer phenomenon. Till today, many numerical models have been developed to discuss the phenomenon but still there is gap of experimentation in the literature.
The present work concerns experimental investigation of viscoelastic fluid flow in a rectangular duct in order to conduct complementary works.
In the first part of thesis, a deep rheological characterisation of aquewous solution of PolyEthylene Oxide (PEO) was carried out to determinate the material parameters , who had significant influence on the flow charecteristics. Gieskus constitutive model was  taken as to identify three material parameters(α), which include charecterisitics relaxation time (λ), viscosity ratio (β), and non-linear parameter.
In the second part of the thesis, a closed-loop flow system was designed consisting of a non-circular transparent channel of suffisent length, a progressive cavity pump with regulator, coriolis flowmeter and an optical measurment system. 2D LDV was employed in two different orientations to completely trace the flow field in the channel at a cross- section. Furthermore, the entire flow fields was plotted at different postions in the same cross-section, by varying the flow rate as well.
It has been the very first work of its nature, since no conrete evidences of experimenatal work about VSFs in the channels has been published till to date. The great challenge in measuring the VSFs is their magnitude. The two transversal components are overshadowed by one principal component , and the difference is second order magnitude. So, in this thesis, we have made an effort to develop a methodology to measure the transversal velocity components perpendicular the axial flow.