Flow of Newtonian and non-Newtonian fluids in concentric and eccentric annuli

Abstract

Three components of mean velocity and the corresponding Reynolds shear stresses have been measured in fully developed concentric and eccentric annulus flows of a Newtonian fluid at bulk-flow Reynolds numbers of 8900 and 26600 and a weakly elastic shear-thinning polymer at effective bulk-flow Reynolds numbers of 1150, 6200 and 9600. The diameter ratio was 0.5 with eccentricities of 0, 0.5 and 1.0, and the use of a Newtonian fluid of refractive index identical to that of the Perspex working section facilitated the measurements by laser velocimetry.With the Newtonian fluid, the distribution of static pressure measurements on the outer wall is shown to be linear, with friction factors for concentric-annulus flows some 8% higher than in a smooth round pipe and for the eccentric flows of eccentricities of 0.5 and 1.0 it was lower by, respectively 8 and 22.5% than that of the concentric-annulus flow. In the former case, the law of the wall was confirmed on both inner and outer walls of the annulus at both Reynolds numbers. This was also the case for the outer wall in the eccentric-annulus flows, except in the smallest gap, but the near-inner-wall flow was not represented by a logarithmic region particularly in the smallest gap. The locations of zero shear stress and zero velocity gradient were displaced by amounts which were, like the secondary flows measured in the eccentric annulus of 0.5, almost within the measurement precision. In the eccentric-annulus flow with eccentricity of 1.0, there was a secondary flow with two circulation cells on each side of the plane of symmetry and with a maximum velocity of 2.2% of the bulk velocity.The measurements with the non-Newtonian fluid were less detailed since refraction limited the flow accessible to the light beams. The average wall shear stress coefficient was similar to that for the Newtonian fluid in the laminar region of the concentric-annulus flow and higher for the two eccentric-annulus flows. Transition was extended to an effective Reynolds number well above that for the Newtonian fluid with a drag reduction of up to 63%. The near-outer-wall flows had logarithmic forms between the Newtonian curve and that of the maximum drag-reduction asymptote, and all fluctuation levels were less than those for the Newtonian fluid, particularly the radial and tangential components.

Predicting turbulence-induced vibration in axial annular flow by means of large-eddy simulations

“…This is reasonably close to the DNS-results of Chung et al (2002), who simulated the same geometry but at a lower Reynolds number (8900) and obtained a position of 0.45 times the channel width and a maximum of 1.18 times the mean flow velocity. There is also reasonable agreement with experimental values of Nouri et al (1993), who located the maximal velocity of 1.22 times the bulk velocity at 0.43 times the channel width. The exact location of the maximum velocity in comparison to the point of zero Reynolds shear stresses has been a point of debate in the literature, with some authors stating that they coincide (Boersma and Breugem (2011)), while others state they do not (Chung et al (2002)).…”

The effect of the inner cylinder rotation on the fluid dynamics of non-Newtonian fluids in concentric and eccentric annuli

“…The work of Nouri et al (1993) stands out among experimental studies on turbulent flow in annular sections. These authors analyzed turbulent flow in vertical annular sections (concentric and eccentric) without the effect of rotation of the inner cylinder.…”

Turbulent flow and heat transfer in eccentric annulus

“…Maximal same eccentricity and diameter ratio and close Reynolds number Re = 8900. Mean velocity profiles of present simulation in the wide and narrow gaps are compared with experimental data of Nouri et al (1993) in the figure 7(a). The agreement is very good in both cases.…”