Flow of viscoelastic fluid in curved tube (Visualization of flow in curved tube and analytical optimization by finite element method)

Abstract

In the present study we report the flow characteristics of a steady flow of viscoelastic fluid in a curved pipe of 90 degree bend. The liquid mode consideration is a model-fluid, which is newly made to investigate the viscoelastic fluid. The flow behavior in the curved pipe was examined by experimentally and analytically at low Reynolds numbers. The visualization of flow in the curved pipe was achieved using a hydrogen bubble method, in which micro-size hydrogen bubbles are generated by a thin platinum wire with passing DC current. The finite element method was used to obtain the analytical solution for the viscoelastic character in the curved pipe. The rheorogical characterization was made by measuring the model-fluid with a precision rheometer. Then the model-fluid was characterized by White-Metzner model and Herschel-Bulkley model as the constitutive equation, for the numerical analysis. The obtained results from the visualization by the hydrogen bubble method were well predicted by the analytical verification, showing distorted plug-flow behavior at the curved pipe, while the Newtonian flow behavior (predicted by the analytical simulation) is almost kept Poiseuille flow behavior. It is found that the pseudoplastic and elasticity in the fluid strongly affect the flow velocity distribution in the curved pipe.

Keywords

• viscoelastic fluid
• herschel-bulkley model
• white-metzner model
• curved pipe
• hydrogen bubble method