Abstract
An investigation is carried out for flow of viscoelatic fluids through a concentric annulus channel converging at the inlet of a pipe, where such a flow configuration is often encountered in a needle part of a stop valve. Experiments are conducted using dilute polyacrylamide water solutions as viscoelastic fluids, with which measurements of pressure and observations with the flow visualization are made. In the experiment, complicated flow patterns which are caused by viscoelastic effects are observed, and the classification of prevailing flow modes is obtaind. By measurement of pressure along the channel wall, it is found that additional pressure loss exists in relation with an appearance of the extra normal stress due to the viscoelasiticity. A correlation is proposed to estimate the pressure characteristic across the entire region of the channel.
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