A numerical study on pressure losses in asymmetric viscoelastic flow through symmetric planar gradual expansions

In this paper, the flow of viscoelastic fluids is numerically studied through a planar gradual (non-abrupt) channel with the expansion ratio of 1:3. Here, the rheological model of the exponential Phan Thien-Tanner (EPTT) is used as the constitutive equation. For discretizing the governing equations, the finite volume method (FVM) employed on the collocated grid and the PISO algorithm is utilized for the velocity-pressure coupling. The main object of the current paper is to investigate the pressure drop and the energy losses of nonlinear viscoelastic flows in gradual expansions. For this purpose, the effects of expansion region and recirculation zones are examined on the pressure drop coefficient and the loss coefficient for different expansion angles and, Reynolds and Weissenberg numbers. The results show that at a constant expansion angle, the total pressure drop and total loss coefficients decrease with an increase in Reynolds or Weissenberg numbers. Moreover, the magnitude of the pressure drop and total loss coefficients increase, in an almost linear way, as the expansion angle increases between 10° to 70°.