Swirling Flow of Viscoelastic Fluid in a Cylindrical Casing

Abstract

The swirling flow of viscoelastic fluid in a cylindrical casing is investigated experimentally, using aqueous solutions of 0.05–1.0 wt% polyacrylamide as the working fluid. The velocity measurements are made using laser Doppler anemometer. The aspect ratios H/R (H: axial length of cylindrical casing, R: radius of rotating disc) investigated are 2.0, 1.0 and 0.3. The Reynolds numbers Re0 based on the zero shear viscosity and the disc tip velocity are between 0.36 and 50. The velocity measurements are mainly conducted for the circumferential velocity component. The experimental velocity data are compared with the velocity profiles obtained by numerical simulations using Giesekus model and power-law model. It is revealed that at any aspect ratios tested the dimensionless circumferential velocity component Vθ’ decreases with increasing Weissenberg number We. The Giesekus model could predict this retardation of circumferential velocity fairly well at small We, but the power-law model could not. The extent of the inverse flow region where the fluid rotates in the direction opposite to the rotating disc is clarified in detail.

PIV study of vortexing during draining from square tanks

“…A numerical analysis of the above problem was conducted by Yu et al [8], and the experimental results have been qualitatively reproduced. The flow field generated in a cylindrical casing with a free surface due to the rotation of a disk at the bottom was studied both experimentally and using numerical simulation by Itoh et al [9]. Viscoelastic fluid with different concentrations of surfactants was used and the extent of the inverse flow region, where the fluid rotates in the direction opposite to the rotating disk, has been clarified in detail.…”

Velocity measurements in confined swirling flow of polymer solutions with vortex shedding

“…3, the experimental data were presented only for r / R Ͻ 0.45 due to the limitation of the resolution of the highspeed camera used. In the figures, solid lines represent data of the axisymmetric numerical simulation 5 for Newtonian fluids at the corresponding Reynolds number. At the axial locations of y / H = 0.02, 0.05, for r / R Ͻ 0.30 within the axisymmetric ring vortex, the mean azimuthal velocity follows the relation of V = 0.9 r⍀ ͓dotted line in Fig.…”

“…Escudier and Cullen 3 observed the double cell structure of the secondary flow of highly shear-thinning carboxymethylcellulose solutions with the elastic number relatively small using flow visualization technique. Recently, Moroi et al 4 and Itoh et al 5 have investigated velocity fields of the confined swirling flow of aqueous polyacrylamide solutions using particle tracking velocimetry ͑PTV͒ and laser Doppler velocimetry ͑LDV͒ measurements, respectively. Moreover, Stokes et al 6,7 performed particle image velocimetry ͑PIV͒ measurements of confined swirling flows of a range of low-to high-viscosity flexible polyacrylamide solutions with a constant viscosity ͑Boger fluids͒ and a semirigid xanthan gum Boger fluid, and clarified the inertia and elasticity effects on velocity fields.…”

The Viscoelastic Swirled Flow in the Confusor

“…Normal stresses exist in viscoelastic media, as discovered in experiments by Garner and Nissan [ 30 ] and interpreted by Weissenberg [ 31 ]. These results triggered the research of the structure of swirled viscoelastic flows in a confined cylinder with a rotating bottom lid [ 32 , 33 , 34 , 35 , 36 , 37 ]) or pipe wall [ 38 ]. Laminar pipe flow with a controllable wall swirl has been studied in [ 39 ] to explore the behavior of inelastic shear-dependent fluids.…”

“…A vortex shedding regime was illustrated using experimental data in [ 35 ]. It was also observed that the dimensionless circumferential velocity decreases with the increase in the Weissenberg number, We [ 34 ]. The obtained results were employed for the development of advanced rotary rheometers with plate-plate and cone-plate measurement systems.…”