Effect of a porous layer on Newtonian and power-law fluids flows between rotating cylinders using lattice Boltzmann method

This study explores numerically the effect of a homogeneous porous layer on the Taylor–Couette flows in finite aspect ratio concentric annular ducts involving non-Newtonian fluids. The porous layer is attached to the outer cylinder which is kept at rest with the end walls, while the inner cylinder is rotating. The gray lattice Boltzmann method is used to obtain the flow field for fluids obeying to the power-law model. The purpose of this contribution is to analyze how the stability of the flow is affected when inserting the porous layer and using a non-Newtonian fluid. Thus, the combined effects of the inner cylinder Reynolds number (Re), the volume fraction of the solid (n s), the porous layer thickness (e) and the power-law index (n), on the flow characteristics are analyzed for a large radius ratio (η) and a finite aspect ratio (Γ). The results show that the presence of the porous layer has a stabilizing effect on the flow structure in the annulus. In fact, it delays the onset of the transition from Couette flow (C.F) to Taylor vortex flow. However, the flow tends to recover the C.F regime for the dilatants and Newtonian fluids as n s increases, while for the pseudo-plastic fluids, the flow shows another bifurcation beyond n s value approximately equal to 0.01.