Vortex-induced vibrations of a cylinder in inelastic shear-thinning and shear-thickening fluids

Abstract

Vortex-induced vibrations (VIV) of a cylinder in a Newtonian fluid is a model problem in fluid–structure interactions and has been studied extensively. In this work, we study the influence of shear-thinning and shear-thickening fluids on the VIV response of a one-degree-of-freedom flexibly-mounted cylinder. We consider a system with a mass ratio of $m^*=2$ and zero structural damping in shear-thinning and shear-thickening power-law fluids at $Re_0 = 15$ and $Re_0 = 200$ , respectively, defined based on the zero-shear-rate viscosity of the fluids. We investigate how the VIV amplitude and frequency, flow forces, and the vorticity contours change as the reduced velocity, $U^*$ , and fluid's time constant, $\lambda$ , change. When the results are compared based on $Re_0$ , shear-thinning fluids enhance the oscillations while shear-thickening fluids suppress them. If, however, we define a characteristic Reynolds number, $Re_{char}$ , based on a viscosity evaluated at the characteristic shear rate, $\dot {\gamma } = U/D$ , then at a constant $Re_{char}$ , the amplitude of response stays very similar for the shear-thinning, shear-thickening and Newtonian fluids. Despite this similarity, the observed far wake is different: shear thinning amplifies the generation of vorticity and reduces the extent of the wake, whereas shear thickening limits the generation of vorticity and extends the wake. Our findings show that the local apparent viscosity observed close to the cylinder placed in shear-thinning or shear-thickening fluids governs the VIV response of the cylinder.

Forced oscillations of a cylinder in the flow of viscoelastic fluids

“…Clearly, the secondary vortices are observed using both models, with minor differences in their details. Additionally, in our previous study (Patel et al 2022) we conducted simulations of inelastic shear-thinning fluids using the Carreau model where we did not see such secondary structures in the vorticity plots. This comparison strengthens the claim that elasticity in the fluid is the driving cause of the secondary vortices that we have observed.…”

“…The solver has been validated in our previous work (Patel, Rothstein & Modarres-Sadeghi 2022). To further validate our numerical results for the specific system considered here, we compared the mean values of drag forces for a case of forced oscillations of a cylinder in Newtonian flow at and and for frequencies varying from to with those presented by Placzek, Sigrist & Hamdouni (2009).…”

Vibro-Acoustic Platelet Activation: An Additive Mechanism of Prothrombosis with Applicability to Snoring and Obstructive Sleep Apnea

“…The loss of acoustic momentum that results from attenuation or dissipation of the sound field in a viscous fluid may result in a nonlinear time-independent fluid motion, i.e., stationary vortices, known as acoustic streaming [36,37,49]. The scale of any acoustic streaming happens on the scale of the wavelength, therefore eliminating that mechanism as a possible activator of platelets.…”

“…In addition to acoustic waves, we have considered the effects of vibration on platelet activation. As shown in Figure 10, the vibrations of the fluid receptacle create ripples on the surface of the fluid, which are known as Faraday waves [49]. Faraday waves are nonlinear standing waves occurring when the vibration frequency exceeds a critical value, the fluid surface becomes unstable, and protrusions/ripples form on the surface.…”

Modal Analysis of the Hydrodynamic Force of a Capsule in a Hydraulic Capsule Pipeline

“…With the exception of internal flow, the interaction between a pipeline and its external flow field, for example, vortex-induced vibration (VIV), is another main factor influencing the safety of a pipeline [18,19]. Thus, some studies have focused on the structure stabilization of a pipeline under its external load.…”