Suppression and augmentation in vortex shedding frequency due to fluid elasticity

IF 2.7 2区工程技术 Q2 MECHANICS

Journal of Non-Newtonian Fluid Mechanics Pub Date : 2024-11-19 DOI:10.1016/j.jnnfm.2024.105348

A. Chauhan, Sana Raffi, C. Sasmal

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引用次数: 0

Abstract

Several previous experimental and numerical studies have demonstrated the suppression of vortex shedding frequency from bluff bodies, such as circular cylinders, due to fluid elasticity induced by adding solid polymer additives to a solvent like water, even in parts per million (ppm) quantities. However, this study reveals a more complex relationship between the two using extensive two-dimensional (2D) direct numerical simulations (DNS) of flows past a circular cylinder at a fixed Reynolds number of 100. Our findings show that the vortex shedding frequency initially decreases with increasing Weissenberg number (a measure of fluid elasticity), reaches a minimum at a critical Weissenberg number, and then increases with further increments in the Weissenberg number. The same non-monotonic trend is also observed in the temporal variation of the spanwise velocity component fluctuation within the flow domain. This study aims to elucidate the reasons behind these non-monotonic trends in vortex shedding frequency and velocity component fluctuations as functions of the Weissenberg number. Our detailed analysis attributes these trends to significant alterations in the vortex-shedding mechanism as fluid elasticity increases due to the appearance of inertio-elastic instability at higher Weissenberg numbers. Our findings also align with limited experimental observations of similar unexpected behaviors in viscoelastic fluids, providing new insights into the underlying mechanisms. Moreover, the study highlights that shear-thinning behavior in viscoelastic fluids counteracts these non-monotonic trends, instead promoting a monotonic increase in vortex shedding frequency with the Weissenberg number. Finally, the 2D simulation results show both qualitative and quantitative agreement with limited three-dimensional (3D) simulations conducted at higher Weissenberg numbers where the flow may transit from 2D to 3D due to the appearance of inertio-elastic instability.

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来源期刊

Journal of Non-Newtonian Fluid Mechanics 物理-力学

CiteScore

5.00

自引率

19.40%

发文量

109

审稿时长

61 days

期刊介绍： The Journal of Non-Newtonian Fluid Mechanics publishes research on flowing soft matter systems. Submissions in all areas of flowing complex fluids are welcomed, including polymer melts and solutions, suspensions, colloids, surfactant solutions, biological fluids, gels, liquid crystals and granular materials. Flow problems relevant to microfluidics, lab-on-a-chip, nanofluidics, biological flows, geophysical flows, industrial processes and other applications are of interest. Subjects considered suitable for the journal include the following (not necessarily in order of importance): Theoretical, computational and experimental studies of naturally or technologically relevant flow problems where the non-Newtonian nature of the fluid is important in determining the character of the flow. We seek in particular studies that lend mechanistic insight into flow behavior in complex fluids or highlight flow phenomena unique to complex fluids. Examples include Instabilities, unsteady and turbulent or chaotic flow characteristics in non-Newtonian fluids, Multiphase flows involving complex fluids, Problems involving transport phenomena such as heat and mass transfer and mixing, to the extent that the non-Newtonian flow behavior is central to the transport phenomena, Novel flow situations that suggest the need for further theoretical study, Practical situations of flow that are in need of systematic theoretical and experimental research. Such issues and developments commonly arise, for example, in the polymer processing, petroleum, pharmaceutical, biomedical and consumer product industries.