Flow-Induced Vibrations of Single and Multiple Heated Circular Cylinders: A Review

This study is an effort to encapsulate the fundamentals and major findings in the area of fluid-solid interaction, particularly the flow-induced vibrations (FIV). Periodic flow separation and vortex shedding stretching downstream induce dynamic fluid forces on the bluff body and results in oscillatory motion of the body. The motion is generally referred to as flow-induced vibrations. FIV is a dynamic phenomenon as the motion, or the vibration of the body is subjected to the continuously changing fluid forces. Sometimes FIV is modeled as forced vibrations to mimic the vibration response due to the fluid forces. FIV is a deep concern of engineers for the design of modern heat exchangers, particularly the shell-and-tube type, as it is the major cause for the tube failures. Effect of important parameters such as Reynolds number, spacing ratio, damping coefficient, mass ratio and reduced velocity on the vibration characteristics (such as Strouhal number, vortex shedding, vibration frequency and amplitude, etc.) is summarized. Flow over a bluff body with wakes developed has been studied widely in the past decades. Several review articles are available in the literature on the area of vortex shedding and FIV. None of them, however, discusses the cases of FIV with heat transfer. In particular systems, FIV is often coupled to heat transfer, e.g., in nuclear power plants, FIV causes wear and tear to heat exchangers, which can eventually lead to catastrophic failure. As the circular shape is the most common shape for tubes and pipes encountered in practice, this review will only focus on the FIV of circular cylinders. In this attempt, FIV of single and multiple cylinders in staggered arrangement, including tandem and side-by-side arrangement is summarized for heated and unheated cylinder(s) in the one- and two-degree of freedom. The review also synthesizes the effect of fouling on heat transfer and flow characteristics. Finally, research prospects for heated circular cylinders are also stated.

Effect of Flow Induced Parameters on the Output of A High Repetition Rate Dye Laser

The factors influencing the optical path stability in a dye laser flow cell are studied numerically and experimentally. A specially designed curved metallic dye flow cell providing a gain medium of 25 mm x 0.5 mm x 0.2 mm along with a compact resonator mechanical assembly is used in the study. The same configuration with gain medium of 15 mm x 0.5 mm x 0.2 mm is successfully used for single mode dye laser. The effects of flow induced vibrations on dye flow cell are studied with and without mechanically coupling it with the resonator structure for flow speeds varying from 1.33 m/s to 6.67 m/s at laser pump position. The effect of the mechanical instability, velocity fluctuation and temperature fluctuations in flowing dye solution on dye laser performance are studied at different flow speeds. These results are compared with the dye laser output parameters and found to be in good agreement. This study is useful in designing a high stability narrowband dye laser.

Flow-Induced Vibrations of a Rotated Square Tube Array Subjected to Single-Phase Cross-Flow

This paper investigates the flow-induced vibration (FIV) and possibility of fluidelastic instability occurrence in a rotated square geometry tube array through a series of experimental tests. All experiments presented here were conducted in water cross-flow. The array pitch spacing ratio of approximately P/D=1.64 is somewhat larger than that commonly found in typical steam generators. The stability of a single flexible tube as well as multiple flexible tubes were investigated. The tubes were free to vibrate purely in the streamwise direction or the transverse direction relative to the upstream flow. A single flexible tube, in the otherwise rigid tube array, was found to undergo large amplitude vibrations (up to 40 % D) in the transverse direction. Tube vibration frequency analysis indicated the presence of two frequency components related to vorticity shedding in the array. This potential vorticity-induced-vibrations (VIV) and potential coupling between VIV and FEI are discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to flow periodicity at low velocity. At significantly high flow velocities, the tubes are found to fully restabilize. This restabilization after VIV locking has not been previously reported as an unlocking result. The present results suggest that the flow-induced vibration of tubes in a rotated square array configuration is significantly more complex than in other geometries, particularly for the streamwise vibration case.

Dataset of Flow-Induced Vibrations on a Pipe Conveying Cold Water

Analysis of flow-induced pipe vibrations has been applied in a variety of applications, such as flowrate inference and leak detection. These applications are based on a functional relationship between the vibration features estimated in the pipe walls and the dynamics related to the flow of the substance. The dataset described in this document is comprised of signals acquired using an accelerometer attached to a pipe conveying cold water at specific flowrate values. Tests were carried out under numerals of the ISO 4064-1/2: 2016 standard and were performed in two measurement benches designed for flowmeter calibration, and a total of 80 flowrate values, from 25 L/h to 20,000 L/h, were considered. For each flowrate value, 3 to 6 samples were taken, so that the resulting dataset has a total of 382 signals that contain acceleration values in three axes and a timestamp in microseconds.

A Review of Computational Methods and Reduced Order Models for Flutter Prediction in Turbomachinery

Aeroelastic phenomena in turbomachinery are one of the most challenging problems to model using computational fluid dynamics (CFD) due to their inherent nonlinear nature, the difficulties in simulating fluid–structure interactions and the considerable computational requirements. Nonetheless, accurate modelling of self-sustained flow-induced vibrations, known as flutter, has proved to be crucial in assessing stability boundaries and extending the operative life of turbomachinery. Flutter avoidance and control is becoming more relevant in compressors and fans due to a well-established trend towards lightweight and thinner designs that enhance aerodynamic efficiency. In this paper, an overview of computational techniques adopted over the years is first presented. The principal methods for flutter modelling are then reviewed; a classification is made to distinguish between classical methods, where the fluid flow does not interact with the structure, and coupled methods, where this interaction is modelled. The most used coupling algorithms along with their benefits and drawbacks are then described. Finally, an insight is presented on model order reduction techniques applied to structure and aerodynamic calculations in turbomachinery flutter simulations, with the aim of reducing computational cost and permitting treatment of complex phenomena in a reasonable time.