Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session X38: Vortex Dynamics and Vortex Flows: Flow-Induced Vibration |
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Chair: James Buchholz, University of Iowa Room: 355 D |
Tuesday, November 26, 2024 8:00AM - 8:13AM |
X38.00001: Vortex-induced Vibrations under Periodically Oscillating Flow Pengyao Gong, Peter M Zaluckyj, Yaqing Jin Laboratory experiments were conducted to investigate the vortex-induced vibrations (VIVs) of a one-degree-of-freedom elastically mounted cylinder in a periodically fluctuating stream within a water channel. The study examined cylinder vibration patterns, hydrodynamic loads, and wake flow dynamics across a wide range of reduced velocities, incoming flow fluctuation frequencies, and flow fluctuation amplitudes using time-resolved particle image velocimetry and a high-resolution load cell. The findings indicated that fluctuating incoming flow reduces cylinder vibration amplitudes, with vortex hydrodynamic loads exhibiting an 'out-of-phase' pattern with cylinder dynamics at lower reduced velocities. Analysis of wake flow dynamics revealed a continuous shift between '2S' and '2P' vortex shedding modes, showing a distinctive hysteresis effect in relation to instantaneous incoming water flow speeds. Furthermore, phase-averaged hydrodynamic load analysis showed that increased incoming flow fluctuation intensities can result in stronger 'out-of-phase' hydrodynamic loads during periods of decreasing incoming flow speeds. |
Tuesday, November 26, 2024 8:13AM - 8:26AM |
X38.00002: Energy harvesting from vortex-induced vibrations of a pendular circular cylinder in cross-flow Francisco J Huera-Huarte A pendulum based on a rigid circular cylinder has been designed to study one degree-of-freedom vortex-induced vibration (VIV) in cross-flow. The system consists of cylinder with mass m, length L and diameter D, that hangs from an air bearing rig to minimise damping, whilst restoring forces are provided by a pair of springs with stiffness constant k. A torsion load cell has been installed at the rotation shaft of the cylinder, between the model and an electromagnetic powder brake. The brake allows to precisely adjust the torque on the shaft. The angular motions of the cylinder are measured using a non-intrusive laser sensor.The cylinder is exposed to a uniform flow with velocity U, generated by the free surface water channel at the Laboratory for Fluid-Structure Interaction (LIFE) at Universitat Rovira i Virgili. |
Tuesday, November 26, 2024 8:26AM - 8:39AM |
X38.00003: Verification of wake branch response regions observed in 2-DOF forced motion of a circular cylinder Brian Mingels, Erdem Aktosun, Jason M Dahl Vortex induced vibrations (VIV) are an essential consideration in the engineering design of long, slender underwater structures subject to currents, such as moorings, line arrays, and pipelines. Some semi-empirical methods used to predict this fluid-structure interaction may utilize forced motion experiments conducted physically or through simulation to estimate forces on a simplified cross-section (such as a rigid circular cylinder) to utilize slender body assumptions for the prediction of the behavior of long, flexible structures. When the cylinder is allowed to vibrate in both the in-line and cross-flow directions, for a given set of kinematic conditions, multiple branches of response have been observed along with unusually excitation forces. Additionally, limited experimental data sets evaluating these forced motions show significant discrepancies in measured forces. In the present study numerical simulations are performed to investigate discrepancies between published 2-DOF forced motion datasets. It is found that results from both datasets can be observed numerically through variation of the initial conditions, indicating additional multiple wake branch response regions that may exist in such datasets, but may not have been observed experimentally. The cause of these differences is a combination of differences in experimental setups and testing environments, coupled with the highly nonlinear nature of VIV in 2 DoF. This observation is significant as it illustrates the sensitivity of such datasets to unobserved nonlinearities that would affect predictions based on forces derived from these datasets. |
Tuesday, November 26, 2024 8:39AM - 8:52AM |
X38.00004: The role of three-dimensionality in wake synchronization characteristics of an oscillatory circular cylinder Youngjae Kim, Vedasri Godavarthi, Laura Victoria Rolandi, Joseph T Klamo, Kunihiko Taira We examine how the three-dimensionality of the wake influences the synchronization characteristics of a circular cylinder at Reynolds number of 300. We determine the theoretical amplitude and frequency conditions that lead to synchronization from the phase-reduction analysis, which projects the full physics of periodic flows to just the phase plane. By comparing a forced two-dimensional wake to a natural three-dimensional wake, we identify the linear effect that wake three-dimensionality plays in reducing the synchronizability of the wake. Phase-reduction analysis, combined with synchronization boundaries obtained from direct numerical simulations, uncover the nonlinear influence of wake three-dimensionality. We found that the chaotic nature of three-dimensional wakes suppresses synchronization to small amplitude cylinder oscillations, while the transition from three- to two-dimensional flow at high-frequency oscillation brings additional capability for synchronization. |
Tuesday, November 26, 2024 8:52AM - 9:05AM |
X38.00005: Polygonal Prisms Oscillating in Flow Sudhansh Tanneru, Adrian G Carleton, Yahya Modarres-Sadeghi We present the results of a series of experiments to investigate the response of different polygonal prisms placed in flow and allowed to oscillate in a direction perpendicular to the direction of incoming flow. Depending on their orientation with respect to the incoming flow, the polygonal prisms undergo Vortex-Induced Vibrations and in some cases also galloping as the reduced velocity is increased. Particle Image Velocimetry results show a variety of shedding patterns in the wake of the cylinder. Flow separation occurs at the sharp edges of the polygons, as expected, and the similarity of the wake patterns for different prisms is largely governed by the downstream orientation of the prisms. These experiments attempt to answer the question ‘how many sides does it take for a polygon to act as a cylinder when oscillating in flow?’ |
Tuesday, November 26, 2024 9:05AM - 9:18AM |
X38.00006: Comparative Analysis of 2D and 3D Simulations of Vortex-Induced Vibrations at Supercritical Reynolds Regime using OpenFOAM Marielle Oliveira, Julio R Meneghini The analysis of Vortex-Induced Vibrations (VIV) at high Reynolds numbers presents significant challenges due to the complex fluid-structure interactions and the limited availability of comprehensive data in experimental data and numerical simulation investigations in the existing literature. As the offshore industry seeks to minimize the impact of VIV on structural components such as platform legs and riser fairings, which are typically cylindrical in shape. In this study, we employed a numerical investigation to analyze the flow field and its forces for a specified range of reduced velocities of 3, 7, 8 and 10 using Computational Fluid Dynamics (CFD) simulations through the Finite Volume Method (FVM) implemented in the OpenFOAM software. Vortex-induced vibrations are analyzed for two different spatial discretization strategies, 2D and 3D investigations were conducted for circular cylinder free to vibrate in the cross-flow direction. In both cases, the characteristic mass-damping parameter used was m^* ζ=0.00858, and the flow regime is given by Re=1×10^6. We employed for the 2D analyses the Unsteady Reynolds Averaged Navier-Stokes (URANS) equation, and (DES) for 3D cases, both turbulence models were employed along with Menter's k−ω SST model as a turbulence closure model, to perform the numerical investigations. The loads on the cylinder are analyzed in terms of nondimensional displacement and time histories of the lift and drag coefficients for each reduced velocity. The key findings in the simulation results include maximum vibration amplitude at reduced velocities 7 and 8, representing an extension of the upper branch for higher reduced velocities, which is expected according to the literature for the supercritical Reynolds regime. |
Tuesday, November 26, 2024 9:18AM - 9:31AM |
X38.00007: Abstract Withdrawn
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Tuesday, November 26, 2024 9:31AM - 9:44AM |
X38.00008: Numerical study of Vortex-Induced Vibration of a Single Flexible Tube within a Non-uniform Tube Array Pegah Mehrabian, Njuki Mureithi Flow-induced vibration can lead to significant damage in heat exchangers. In small modular reactors, helical coil steam generators (HCSGs) may potentially be susceptible to vortex-induced vibrations due to single-phase flow on the shell side. This study examines vortex-induced vibrations in a cross-section of HCSGs focusing on a non-uniform tube array. The non-uniform tube array under consideration combines a normal square and a rotated triangle geometry with a transverse spacing ratio (Xt) of 1.3 and a longitudinal spacing ratio (Xl) of 1.5. Through two-way coupling, the fluid force is transferred to the tube, and then the incremental displacement of the tube is transferred back to the fluid domain at each time step. A validation case analysis (Khalak & Williamson, 1996) was conducted prior to the real case study to demonstrate the accuracy of the URANS model, specifically the turbulence model, k-ω SST. The Strouhal number for the non-uniform tube array is different from those obtained for the two fundamental tube patterns (i.e. Normal square and Rotated triangle). This particular Strouhal number is close to the rotated triangle tube pattern Strouhal number. For the non-uniform tube array, one flexible tube, which is free to vibrate in the transverse direction, is considered for three different sections of the helical geometry. Simulations for three different flow velocities were compared, and the onset of lock-in was observed. The results for the non-uniform array show a slightly lower predicted frequency, but the margin for lock-in is reasonably accurate. The distinction between vortex-induced vibration and fluid-elastic instability is intricately tied to the position of the flexible tubes. It has been determined that the section with the rotated triangle configuration within the non-uniform tube array predominantly influences the critical flow velocity and the lock-in region. A comparison was conducted between undamped tube vibration and vibration with low (structural) damping for one flexible tube to investigate the influence of damping on the flow periodicity lock-in dynamics in the tube array. Adding even small structural damping to the tubes significantly increases the critical flow velocity for the non-uniform tube array. |
Tuesday, November 26, 2024 9:44AM - 9:57AM |
X38.00009: Modeling and simulation of flow-induced vibrations of elastically mounted flexible structures. Gaurav Sharma, Rajneesh Bhardwaj We present the Flow-Induced Vibration modeling and the response of an elastically mounted rigid cylinder with an attached flexible plate at a low Reynolds number of 150. The spring stiffness and plate elasticity are varied to simulate the FIV responses of the system from the elastically mounted rigid structure to the rigidly mounted flexible structure. We model the system using a surface force modification approach, accounting for the cylinder's stiffness and damping forces while passing the flow forces to the structure. This eliminates the need to sequentially solve for the rigid body displacement and flexible body deformation in separate sub-steps during Fluid-Structure Interaction (FSI) implementation. The results show good agreement with the COMSOL implementation (commercial solver). The present study highlights the deviations in FIV response from the previous studies and the associated approximations. The study shows that while the rigid cylinder-plate system is susceptible to galloping, the flexible system can be designed to minimize FIV. |
Tuesday, November 26, 2024 9:57AM - 10:10AM |
X38.00010: Dynamics of a flexible beam in the wake of a cylinder in shear-thinning flow Han Gong, Umang N. Patel, Jonathan P Rothstein, Yahya Modarres-Sadeghi Fluid-Structure Interaction (FSI) between shear-thinning flow and a flexible structure is studied numerically. The simulation is conducted by coupling the fluid solver, OpenFOAM, and the solid solver, deal.II, through an open-source library preCICE. We model a two-dimensional fluid domain with an incompressible, shear-thinning fluid that resembles the rheological properties of human blood with uniform and steady inlet flow. The shear-dependent viscosity is described using the Carreau model. The solid structure is an elastic beam modeled as incompressible, uniaxial neo-Hookean material, placed in the wake of a fixed, rigid, non-slip cylinder. We study the response of the beam for a range of zero-shear Reynolds numbers and with beams of different lengths. The degree of shear-thinning is varied by changing the Carreau number while keeping the Reynolds number constant. We study the changes in the frequency and amplitude of the beam’s oscillations with the Rynolds number and the Carreau umber. We show that the shear-thinning effects cause flow instability at subcritical Reynolds numbers, and cause oscillations of the flexible beam in the wake of the cylinder. |
Tuesday, November 26, 2024 10:10AM - 10:23AM |
X38.00011: Time-Resolved 3D Wake Reconstruction of a Circular Cylinder Undergoing Vortex-Induced Vibration Using 2D Measurements Mohammadhossein Kashefi, Peyman Khazaee Kuhpar, Banafsheh Seyed-Aghazadeh Due to the high costs associated with three-dimensional (3D) flow measurement techniques, there is a strong need for more accessible methods to obtain 3D flow fields using fewer measurements and more affordable devices. This study addresses this need by focusing on time-resolved 3D flow reconstruction in the wake of a circular cylinder undergoing vortex-induced vibration (VIV), using two-dimensional, three-component (2D-3C) velocity images. Snapshot optimization (SO) and averaging SO techniques, with defined threshold errors, are employed to use the 2D images and reconstruct a volumetric flow field. Experimental data is acquired using volumetric Particle Tracking Velocimetry (PTV) measurements, and the required 2D data for reconstruction is extracted. The reconstructed 3D flow is then compared with the original volumetric data. The study spans various Reynolds numbers within the VIV lock-in range. Results indicate that the averaging SO technique reconstructs the flow with high accuracy and minimal discontinuity along the spanwise direction, outperforming the SO method. Additionally, the time-resolved flow field obtained using the averaging SO method is further analyzed through Proper Orthogonal Decomposition (POD) technique. |
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