粘弾性流体の狭あい部を通る流れにおける応力分布

抄録

Many non-Newtonian visoous fluids are recently used in practice, and in consequence the chances of handling these fluids have increased in many fields. However, at present the rheological equation is not yet established for the viscoelastic non-Newtonian fluids. Experimental studies are required, therefore, of viscoelastic flow concerning its stress analysis. One of the most efficient experimental methods is considered to be the photoelastic procedure, in view of the fact that the viscoelastic fluids with velocity gradients have birefringence effect.
In this paper, the results of photoelastic measurements of viscoelastic flows through narrowed portions are reported. The flow was produced in rectangular vessels as two-dimentional flow by applying pressure to the fluid, and the narrowed portions were formed by applying triangular or rectangular projections to the two opposite walls. As the viscoelastic fluid, taking the homogeneity, fluidity and transparency as well as the birefringence effect of the material into consideration, Epikote fluid was employed. An ordinary photoelastic apparatus was used, and clear isochromatic and isoclinic patterns of stressed viscoelastic fluid were obtained. The experimental results may be summarized as follows. In general, the shear stress plays an important role for the mechanical degradation of highpolymer fluids. It is significant, therefore, to predict the amount of shear stress in the flow of such fluids, In the viscoelastic flows through the narrowed portions experimented in this study, the maximum shear stress appeared at the corner of each projection. Moreover, the shear stresses along the flow direction midway between both the projections showed peak values at the points a short distance ahead or behind the corners of the projections.