In rock grouting, idealized 2D-radial laminar flow of yield stress fluids (YSF) is a fundamental flow configuration that is used for cement grout spread estimation. A limited amount of works have presented analytical and numerical solutions on the radial velocity profiles between parallel disks. However, to the best of our knowledge, there has been no experimental work that has presented measured velocity profiles for this geometry. In this paper, we present velocity profiles of Carbopol (a simple YSF), measured by pulsed ultrasound velocimetry within a radial flow model. We describe the design of the physical model and then present the measured velocity profiles while highlighting the plug-flow region and slip effects observed for three different apertures and volumetric flow rates. Although the measured velocity profiles exhibited wall slip, there was a reasonably good agreement with the analytical solution. We then discuss the major implications of our work on radial flow.
Polyaniline (PANI)-LiNi0.5La0.02Fe1.98O4 nanocomposites were synthesized by an in situ polymerization of aniline in the presence of LiNi0.5La0.02Fe1.98O4 ferrite. The products were characterized by Fourier transform infrared (FTIR), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). FTIR spectra and XRD indicated the formation of the PANI-LiNi0.5La0.02Fe1.98O4 composites. AFM study was shown that the average size of samples was less than 100 nm and the ferrite particles had an effect on the morphology of composites. The nanocomposites under applied magnetic field exhibited the hysteresis loops of the ferrimagnetic nature, the saturation magnetization and the coercivity varied with the ferrite content. The bonding model for the composites was also studied. 相似文献
Numerical simulations were carried out to investigate the turbulent flow with free-surface vortex in an uncovered unbaffled stirred tank. An Eulerian–Eulerian multiphase flow model coupled with a volume-of fluid method was applied to capture the gas–liquid interface and describe the flow field in the tank. Turbulence is computed using a Reynolds stress model with seven equations. The reliability and accuracy of the simulations are verified by comparing the predicted free surface profiles and power numbers with experimental data in the literature. The overall agreements between the simulation results and experimental measurements are obtained. The simulation results show that vortex on the liquid free surface in the uncovered unbaffled tank can be divided into central zone and peripheral zone, and the critical radius of the two zones keeps almost unchanged with enhancing of impeller speeds. At the same impeller speed, vortex becomes deeper and larger with increasing of impeller diameter. However, vortex shape changes not very much with increasing of impeller diameter under the same power consumption. Impeller clearance has no significant influence on the vortex shape. Circumferential flow is dominant in the uncovered unbaffled tank, and the flow field can be divided into forced vortex region and free vortex region. Power numbers in uncovered unbaffled stirred tanks decrease slightly with increasing of the Reynolds number, and are far lower than that in baffled stirred tanks. 相似文献