Research On The Flow,Heat And Mass Transfer Of Non-newtonian Fluid Thin Film

The research on flow,heat and mass transfer of Non-Newtonian fluid thin film can provide theoretical guidance for the optimization of process planning for polymer film materials and improvement of product performance.In this paper,the flow,heat and mass transfer characteristics of viscoelastic fluid film as well as the flow and heat transfer laws of power-law fluid film over a stretching sheet are studied.The new constitutive relations considering the characteristics of both viscoelastic fluids and power law fluids are formulated to study the rheological properties of welan gum solutions.The main researches are as follows:1)This paper investigates the flow,heat and mass transfer characteristics of upper-convected Oldroyd-B fluid thin film over an unsteady stretching sheet.The relaxation time of the heat fluxes and the relaxation time of mass fluxes are introduced into classical Fourier's and Fick's laws respectively.Depending on unsteady Cattaneo-Christov double diffusion theory and constitutive equation of upper-convected Oldroyd-B fluid,the relaxation-retardation viscous dissipation and chemical reaction with relaxation-time characteristicis are developed.Furthermore,the governing equations of upper-convected Oldroyd-B fluid thin film flow and heat transfer are obtained.The analytical solutions of the boundary layer problems are obtained by double-parameter transformation expansion method?DPTEM?.The conclusions can be revealed:Increasing unsteadiness parameter causes a rise in film thickness for?2>?1,but a decline as?2<?1.Moreover,the temperature enhances with rising values of retardation time when?2<?1,while the contrary behaviors are observed when?2>?1.Furthermore,unsteadiness parameter has the opposite influences on the concentration in the cases of?₂>?₁ and?₂<?₁.2)This study investigates the flow and heat transfer laws of power-law nanofluid thin film induced by an unsteady stretching sheet.A modified Fourier's law is proposed under assuming thermal conductivity is power-law-dependent on both velocity gradient and temperature gradient.Furthermore,the convective heat transfer boundary condition also been modified.Depending on the wall slip characteristics of polymers,the power-law velocity slip boundary condition is introduced.Moreover,the influences of varied pressure gradient and variable heat absorbed on the thin film flow and heat transfer are studied.The analytical solutions of the similarity ordinary differential systems are obtained by DTM-NIM which is constituted by differential transform method?DTM?coupled with Newton Iteration method?NIM?.Conclusions:The two adjacent velocity profiles intersect at one point which moves from a far-field region to the stretching sheet for increasing velocity slip parameter.The effect of pressure on film thickness is stronger than that on velocity.For the modified Fourier's law,temperature gradient has more remarkable influence on heat transfer compared with velocity gradient.3)This research studies the constitutive relation of welan gum solutions which simultaneously characterize the features of power law fluids and viscoelastic fluids.Based on the experimental data acquired by rheometer,a new constitutive relation is introduced:Maxwell-Powerlaw model to investigate the rheological characteristics of welan gum solutions.The theoretical analysis and the analytical methods in this paper can provide theoretical support for the flow,heat and mass transfer of non-Newtonian fluids thin film.Meanwhile,the accuracies of the analytical methods in this paper are confirmed by comparing the present results with the previous.This also offers a reference for solving ordinary differential equations in other engineering fields.