POD analysis of oscillating grid turbulence in water and shear thinning polymer solution

Abstract

Oscillating grids are frequently used with water and Newtonian fluids to generate controlled turbulence and mixing. Yet, their use with shear thinning fluids still requires experimental characterization. Proper orthogonal decomposition (POD) is applied to PIV measurements of the flow generated by an oscillating grid in water and a shear thinning dilute polymer solution (DPS) of xanthan gum. The aims are to investigate the ability of POD to isolate periodic flow structures, and to use it to describe the effects of the shear thinning property. A dominance of the low order POD modes is evidenced in DPS. The methods applied in blade stirred tanks to identify oscillatory motion fail here. However, a strong mode coupling in the grid swept region is observed, determined by the working fluid and by an underlying chaotic nature of the flow. Possibilities of reconstructing turbulence properties using high order modes are discussed.

Flow stirred by open turbine: A modal analysis of multiscale flow characteristics

“…PIV measurements are subject to various factors that affect their accuracy, including the nature of the flow field, the quality of flow field measurements, and the data interpolation method. 25,26 The total measurement error typically comprises systematic and random errors. In this experiment, the error resulting from pixel resolution, determined by factors such as particle diameter and peak locking, 27,28 constituted the primary source of systematic error.…”

Towards Reduced Order Models via Robust Proper Orthogonal Decomposition to Capture Personalised Aortic Haemodynamics

“…A similar 'triadic interaction' has been reported by Gabelle et al [34] in a stirred tank flow (who attributed the behaviour to non-linear interactions between the modes), and by Lacassagne at al. 370 [35] in an oscillating grid flow.…”

“…A similar 'triadic interaction' has been reported by Gabelle et al [34] in a stirred tank flow (who attributed the behaviour to non-linear interactions between the modes), and by Lacassagne at al. 370 [35] in an oscillating grid flow. Figures 6-8 show the comparison between the FOMs at three instants of the cardiac cycle (peak systole, deceleration and diastole), and the reconstructed velocity fields of 375 ROMs using Φ1-2, Φ1-5 and Φ1-10.…”

Turbulent mass transfer near gas-liquid interfaces in water and shear-thinning dilute polymer solution

“…Turbulence is generated in the liquid phase by an oscillating grid device previously described and used in [25,37,19,38,39], and sketched in figure 2.…”