Lock-in regimes for Vortex-Induced Vibrations of a cylinder attached to a bistable spring

Badhurshah, Rameez; Bhardwaj, Rajneesh; Bhattacharya, Amitabh

doi:10.1016/j.jfluidstructs.2019.102697

Cited by 20 publications

(21 citation statements)

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“…Recently, Ellingsen and Amandolese [15], have also utilized the kinetic energy budget of the cylinder, along with the WOM equations, to demarcate the synchronization regimes for VIV of cylinder attached to linear spring. As part of the theoretical analysis, a constraint between the amplitude and frequency of the structure was obtained, which looks very similar to the EC curve derived in Badhurshah et al [13]. However, the analysis presented in Ref.…”

Section: Introductionsupporting

confidence: 77%

“…We also performed numerical simulations of the WOM equations for VIV with both linear and bistable springs, as reprted in Ref. [13]. We found an excellent qualitative agreement with the predictions from our theory with results from the WOM simulations.…”

Section: Introductionsupporting

confidence: 73%

“…The experimental results report a 138 % and 29 % increment in the synchronization region and harvested power, respectively. Bistability can also arise naturally during angular oscillations induced by VIV [4,11,12] In prior work [13], we have used a Wake Oscillator Model (WOM) [14] to study VIV of cylinders attached to a bistable spring. Compared to VIV with linear springs, we found a significant increase in the range of reduced velocities over which lock-in occurs for VIV with bistable springs, especially when the distance between the potential wells is reduced.…”

Section: Introductionmentioning

confidence: 99%

“…Our simulations are performed using a well-validated solver, based on Immersed Boundary method (IBM) [19]. To further understand the validity of the theory proposed in [13], we will also try to verify the existence of the EC curve using the CFD simulations, which can then in turn explain the results from the CFD simulations at least qualitatively. We will also compare and examine the vortex shedding patterns for VIV with linear and bistable springs respectively.…”

Section: Introductionmentioning

confidence: 99%

“…However, no theoretical explaination was provided here on how the spring nonlinearity increased the lock-in regime, and the study did not consider the effect of bistability in the spring potential. Furthermore, this study was performed at low mass ratio, for which our prior theory [13] is not strictly applicable.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulation of Vortex-Induced Vibration With Bistable Springs : Consistency with the Equilibrium Constraint

Badhurshah,

Bhardwaj,

Bhattacharya

2021

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We present results from two-dimensional numerical simulations based on Immersed Boundary Method (IBM) of a cylinder in uniform fluid flow attached to bistable springs undergoing Vortex-Induced Vibrations (VIV). The elastic spring potential for the bistable springs, consisting of two potential wells, is completely defined by the spacing between the potential minima and the depth of the potential wells. We perform simulations of VIV with linear spring, as well as bistable springs with two different inter-well separations, over a wide range of reduced velocity. As expected, large oscillation amplitudes correspond to lock-in of the lift force with the natural frequency of the spring-mass system. The range of reduced velocity over which lock-in occurs is significantly higher for VIV with bistable springs compared to VIV with linear springs, although the maximum possible amplitude appears to be independent of the spring type. For VIV with bistable springs, the cylinder undergoes double-well oscillations in the lock-in regime. Range of reduced velocity over which lock-in occurs increases when the inter-well distance is reduced. The vortex shedding patterns and amplitude trends look similar at the same equivalent reduced velocity for the different springs. The results here are consistent with our prior theory, in which we propose a new "Equilibrium-Constraint (EC)" based on average kinetic energy budget of the structure. For a given spring potential, the intersection of natural frequency curves with the EC curve yields the possible range of reduced velocities over which lock-in should occur. Our numerical simulations show a collapse of the amplitude-versus-structure frequency data for all the simulations onto roughly the same curve, thus supporting the existence of the EC, and providing an explanation for the trends in the VIV oscillations. The present study provides fundamental insights into VIV characteristics of bistable springs, which may be useful for designing broadband energy harvesters.

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Section: Introductionsupporting

confidence: 77%

Section: Introductionsupporting

confidence: 73%