Flow induced vibration

In this present work the development, the implementation and the results interpretation of an Immersed Boundary Method, in a bi-dimensional Cartesian grid are shown. Three interpolations for the Immersed boundary correction were implemented and tested in a cavity flow with analytical solution. The second order of convergence from the FV discretization was obtained with a polynomial regression using material points and neighbor fluid cells based on the Least Square Method. The verification of the model was performed by comparison of the obtained results with computational data from the literature in steady laminar flows. Both qualitative and quantitative features of the flow were considered and showed considerable resemblance with the literature. In the moving boundary chapter verification was achieved by comparison with both experimental and computational data. The developed code allowed applications for computational modeling of moving boundaries immersed in fluid flows, accurately representing the behaviour of the fluid and the interactions between the fluid and the body's structure. The study of a portion from a winding Eucalyptus peel tube, one of the most common reasons for the propagation of forest wild fires, is performed and the aerodynamic drag force is shown. The comparison of the results with both empiric and computational data confirmed that the method is reliable to solve problems of immersed boundaries and that the computational cost can be decreased for this type of calculations.

Flow-induced instabilities are one of the major challenges in the design of aerospace structures. Numerous passive and active control methods have been used to reduce the flow-induced oscillations of square cross-section cylinder as the basic geometry for structures with sharp corners. The suction and blowing flow control method are one of the most effective approaches for controlling the flow and consequently reducing the vibrations resulting from the aerodynamic forces, which so far are not considered for an elastically-mounted square cylinder which fluctuates freely in the transverse direction. Therefore, in this paper, suction and blowing flow control methods have been used separately to suppress flow-induced oscillations. In the suction-based method, a slut is placed on the front surface of the cylinder and in the blowing-based method another slot is inserted on the back surface of the cylinder. In the present study, the effect of suction and blowing velocities as well as the effect of suction and blowing slut lengths on the efficiency of the flow control approach was evaluated. According to the flow-structure interaction simulations, it is observed that the applied flow control method has been able to reduce flow-induced vibrations appropriately.

The passive safety systems (PSSs) within water-cooled reactors are meticulously engineered to function autonomously, requiring no external power source or manual intervention. They depend exclusively on inherent natural forces and the fundamental principles of reactor physics, such as gravity, natural convection, and phase changes, to manage, alleviate, and avert the release of radioactive materials into the environment during accident scenarios like a loss-of-coolant accident (LOCA). PSSs are already integrated into such operating commercial reactors as the Advanced Pressurized Reactor-1000 MWe (AP1000) and the Water-Water Energetic Reactor-1200 MWe (WWER-1200) are adopted in most of the upcoming small modular reactor (SMR) designs. Examples of water-cooled SMR PSSs are the passive emergency core-cooling system (ECCS), passive containment cooling system (PCCS), and passive decay-heat removal system, the designs of which vary based on reactor system-design requirements. However, understanding the accident-event progression and phases of a LOCA is pivotal for adopting a specific PSS for a new SMR design. This study covers the accident-event progression for direct vessel injection (DVI) small-break loss-of-coolant accident (SB-LOCA), associated physics phenomena, knowledge gaps, and important figures of merit (FOMs) that may need to be evaluated and assessed to validate thermal-hydraulics models with an available experimental dataset to support new SMR design and development.

Recent developments in materials and cost reduction have led the study of the vibrational stability of pipelines conveying fluid to be an important issue. Nowadays, this analysis is done both by means of simulation with specialized softwares and by laboratory testing of the preferred materials. The former usually requires of complex modelling of the pipeline and the internal fluid to determine if the material will ensure vibrational stability; and in the latter case, each time there is a mistake on the material selection is necessary to restart all the process making this option expensive. In this paper, the classical mathematical description of the dynamic behavior of a clamped-pinned pipeline conveying fluid is presented. Then, they are approximated to a Hamiltonian system through Garlekin’s method being modelled as a simple linear system. The system stability has been studied by means of the eigenvalues of the linear system. From this analysis, characteristic expressions dependen...

In this work, a hybrid numerical approach to predict the vibrational responses of planar structures excited by a turbulent boundary layer is presented. The approach combines an uncorrelated wall plane wave technique with the finite element method. The wall pressure field induced by a turbulent boundary layer is obtained as a set of uncorrelated wall pressure plane waves. The amplitude of these plane waves are determined from the cross spectrum density function of the wall pressure field given either by empirical models from literature or from experimental data. The response of the planar structure subject to a turbulent boundary layer excitation is then obtained from an ensemble average of the different realizations. The numerical technique is computationally efficient as it rapidly converges using a small number of realizations. To demonstrate the method, the vibrational responses of two panels with simply supported or clamped boundary conditions and excited by turbulent flow are considered. In the case study comprising a plate with

The response of a spring-mounted circular cylinder constrained to vibrate with a single degree of freedom transverse to an oscillating stream is investigated using twodimensional flow simulations. The Keulegan-Carpenter number was set at large values with the ratio of the oscillatory flow frequency f o to the natural frequency of the cylinder f n assuming values of f o /f n = 0.01, 0.02, and 0.04, so as to investigate the effect of veryslowly-varying reduced velocity on the transient response. A maximum reduced velocity of 5, corresponding to a maximum Reynolds number of 150, was employed in all cases. Under these conditions, the cylinder underwent intermittent vortex-induced vibration (VIV) with amplitude modulations at the period of the oscillatory flow. Maximum VIV amplitudes of approximately half diameter occurred near the end of the flow acceleration stage. Pronounced hysteresis was observed in the plots of the ensemble-averaged amplitude and frequency, both being greater during the deceleration stage than during the acceleration stage at the same instantaneous reduced velocity over a significant part of the flow half period. The hysteresis was found to be related to 'transient' operating points that, in the space of normalized amplitude and frequency, join smoothly the distinct branches of steady-VIV where operating points do not exist (for the same system with varying the reduced velocity). The main deterministic VIV features were similar at all three frequency ratios examined but the stochastic features became more pronounced as f o /f n was increased. We also found that the cylinder motion and the driving fluid force sometimes were not synchronized around the point of maximum flow velocity, although this point corresponds to well within the synchronization range in steady-VIV.

In this work, we considered the flow around two circular cylinders of equal diameter placed in tandem with respect to the incident uniform flow. The upstream cylinder was fixed and the downstream cylinder was completely free to move in the cross-stream direction, with no spring or damper attached to it. The centre-to-centre distance between the cylinders was four diameters, and the Reynolds number was varied from 100 to 645. We performed two-and three-dimensional simulations of this flow using a Spectral/hp element method to discretise the flow equations, coupled to a simple Newmark integration routine that solves the equation of the dynamics of the cylinder. The differences of the behaviours observed in the two-and three-dimensional simulations are highlighted and the data is analysed under the light of previously published experimental results obtained for higher Reynolds numbers.

This research delves into the complex dynamics of high-pressure, hot, and dynamic liquids flowing through piping systems. To better understand the various factors that affect the torsional vibration of these liquids, the study uses a coupled nonlinear partial differential equation to analyze generating variables such as fluid flow heat flux, mass ratio, pipe thickness, internal pressurization, vertical motion, longitudinal direction kinetic energy of the inner fluid, and crosssectional area change. The ANSYS CFD R2022a software is used to simulate the model, and a threedimensional model is used to investigate the dynamic behavior of the thin pipe. The numerical modal analysis is performed in the configuration of fluid-structure interaction, and the study also examines the vibratory behavior of the fluid-conveying pipe. The results indicate that the velocity was 7.5% lower in the pipe with plaque model than in the normal pipe model, while pressure and WSS were 94.9% and 74.41% higher, respectively. The study also conducts parametric studies on the effect of temperature, pressure drop, and velocity change on the frequencies. Additionally, the research suggests that a gas column input signal exists in the pipe, which can cause severe vibration when it comes into contact with unreasonable vibration. This study highlights the importance of determining the ideal design for pipes to restore their usual functions and avoid excessive vibration."

Great progress has been made in the research on hydraulics, hydrodynamics and hydroinformatics over the past few decades. This includes theoretical, experimental and numerical studies, leading to a new understanding and knowledge of water-related problems, covering a wide range of topics and applications such as hydrology, water quality, river and channel flows. For example, coherent vortex structures in a backward-facing step flow and secondary flow in an open channel bend are measured using PIV; the flow through a Y-shaped confluence channel partially covered with rigid vegetation on its inner bank is measured by ADV. Meanwhile, the velocity decay of an offset jet in a narrow and deep pool, and the skimming flow over a pooled stepped spillway, are studied numerically. In addition, mechanisms for sediment transport due to riverbank failure and a method of predicting maximum scour depth are investigated, and cavitation bubble collapse and its impact on a wall are studied. In order to accelerate knowledge transfer in resolving engineering problems, this Special Issue reports both on the state-of-the-art of the aforementioned research topics, and on advances in sediment transport dynamics, two-phase flows, flow-induced vibration, and hydropower station hydraulics. The goals of this Special Issue are to improve our understanding of the foregoing flow problems and to stimulate future research in these areas, aiming for an improved quality of life.

To reduce environmental pollution like global warming and air pollution has highly promoted the research of application of study of renewable fuel like bio-diesel and its blends to internal combustion engine. In this project practically investigated & compared the performance & emission of 4 stroke single cylinder diesel engine using diesel & diesel-cotton seed biodiesel blends with additives. In diesel, blends are 10%, 20%, 30%, 40%, 50%, 60%, 70% of cotton seed biodiesel with each 10 ml of Nitromethane and Nitroethane in each blend by volume basis. For existing CI engine with brake specific fuel consumption, brake thermal efficiency are improved and emission of NOx and smoke are reduced without modification in engine. To carry the test we used computerized 4 stroke single cylinder kirlosker make CI engine & fuel efficiency monitor for emission analysis. Performance evaluation contains evaluation of brake power, friction power, brake specific fuel consumption, brake thermal efficiecy. Emission analysis contain analysis of co%, no (ppm), no2 (ppm), exhaust gas temp (0c).

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International licence Newcastle University ePrints-eprint.ncl.ac.uk Assi GRS, Srinil N, Freire CM, Korkischko I. Experimental investigation of the flow-induced vibration of a curved cylinder in convex and concave configurations.

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The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier-Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upperairway disorders.

The flow characteristics of inline and one slotted cylinder placed in a fin tube heat exchanger model are experimentally investigated using Partical Image Velocimetry (PIV) for Reynolds numbers of 1500 and 4000. In this study, the Reynolds number is calculated based on the cylinder diameter. Qualitative flow visualization was initially employed in order to observe the overall nature of the vortical flow patterns of cylinders. The flow interactions in the streamwise bases of the cylinder with a flat plate surface results in two dimensional vorticity <>, streamline topology <> and velocity vector map <V> behavior. Keywords—confined flow, vorticity, staggered cylinders, slot

Submitted for the DFD15 Meeting of The American Physical Society Hysteretic memory and end plate effects on the response of a flexible cylinder undergoing Vortex-Induced Vibrations (VIV) ERSEGUN DENIZ GEDIKLI, JASON M DAHL, Ocean Engineering Department, University of Rhode Island-The response of rigid cylinders undergoing VIV has been observed to be hysteretic with respect to the nominal reduced velocity, as transition of the wake is delayed dependent on whether the flow has been slowed down or sped up. In the present study, a similar behavior is observed for a flexible, tension-dominated cylinder, however the hysteretic behavior is shown to affect the transition between excited modes. The test cylinder has diameter of 6.35 mm, aspect ratio of 40 and mass ratio of 3.76. The dynamic response of the cylinder is measured visually, by tracking 26 dots along the span of the cylinder using two high-speed cameras between the Reynolds number of 1080 and 4660. It is observed that a clear memory effect exists, where the speed at which transition between the first mode and second mode excitation in the cross-flow direction changes dependent on whether the flow is increasing or decreasing in speed. A second series of experiments is conducted to investigate end plate effects on the flexible cylinder. Experiments are conducted with and without an end plate located at the end pivot point on the cylinder. Clear differences are observed between each condition illustrating the strong threedimensional behavior of vortex shedding behind the flexible cylinder.

In the current work, we investigate the influence of unsteady partial cavitation on the fluid-structure interaction of a freely vibrating hydrofoil section at high Reynolds numbers. We consider an elastically-mounted NACA66 hydrofoil section that is free to vibrate in the transverse flow direction. Cavitating flow dynamics coupled with the transverse vibration are studied at low angles of attack. For this numerical study, we employ a recently developed unified variational fluid-structure interaction framework based on homogeneous mixture-based cavitation with a hybrid URANS-LES turbulence modeling. We first validate the numerical implementation against the experimental data for turbulent cavitating flow at high Reynolds numbers. For the freely oscillating hydrofoil, we observe large-amplitude vibrations during unsteady partial cavitating conditions that are absent in the non-cavitating flow configuration. We identify a frequency lock-in phenomenon as the main source of sustained large-amplitude vibration whereby the unsteady lift forces lock into a sub-harmonic of the hydrofoil natural frequency. During the cavity collapse and shedding, we find a periodic generation of clockwise vorticity, leading to the unsteady lift generation. We determine the origin of this flow unsteadiness at the vicinity of the trailing edge of the hydrofoil through the interplay between the growing cavity with the adverse pressure gradient. The flow-induced structural vibration is also observed to have a consequent impact on the cavity dynamics. In the frequency lock-in regime, large coherent cavitating structures are seen over the hydrofoil suction surface undergoing a full cavity growth-detachment-collapse cycle. For the post-lock-in regime, the cavity length is shorter and the attached cavity length is observed to undergo high frequency spatially localized oscillations. In this regime, cavity shedding is primarily limited to the cavity trailing end and the frequency of a complete cavity detachment and shedding event is reduced. This work has a practical relevance to the cavitation-induced vibration of marine propellers with the target of noise mitigation by active or passive control mechanisms.

In the current work, we investigate the influence of unsteady partial cavitation on the fluid-structure interaction of a freely vibrating hydrofoil section at high Reynolds numbers. We consider an elastically-mounted NACA66 hydrofoil section that is free to vibrate in the transverse flow direction. Cavitating flow dynamics coupled with the transverse vibration are studied at low angles of attack. For this numerical study, we employ a recently developed unified variational fluid-structure interaction framework based on homogeneous mixture-based cavitation with a hybrid URANS-LES turbulence modeling. We first validate the numerical implementation against the experimental data for turbulent cavitating flow at high Reynolds numbers. For the freely oscillating hydrofoil, we observe large-amplitude vibrations during unsteady partial cavitating conditions that are absent in the non-cavitating flow configuration. We identify a frequency lock-in phenomenon as the main source of sustained large-amplitude vibration whereby the unsteady lift forces lock into a sub-harmonic of the hydrofoil natural frequency. During the cavity collapse and shedding, we find a periodic generation of clockwise vorticity, leading to the unsteady lift generation. We determine the origin of this flow unsteadiness at the vicinity of the trailing edge of the hydrofoil through the interplay between the growing cavity with the adverse pressure gradient. The flow-induced structural vibration is also observed to have a consequent impact on the cavity dynamics. In the frequency lock-in regime, large coherent cavitating structures are seen over the hydrofoil suction surface undergoing a full cavity growth-detachment-collapse cycle. For the post-lock-in regime, the cavity length is shorter and the attached cavity length is observed to undergo high frequency spatially localized oscillations. In this regime, cavity shedding is primarily limited to the cavity trailing end and the frequency of a complete cavity detachment and shedding event is reduced. This work has a practical relevance to the cavitation-induced vibration of marine propellers with the target of noise mitigation by active or passive control mechanisms.

In this paper, power transfer of an elastically mounted body under the influence of fluidelastic galloping is analysed. The quasi-steady state model equations are first analysed to find suitable governing parameters. It is shown that, as well as Re, the system is a function of three dimensionless groups: a combined mass-stiffness parameter, Π 1 ; a combined mass-damping parameter, Π 2 ; and mass ratio, m n. Data obtained by numerically integrating the quasi-steady state equations show that for high values of Π 1 , the power extracted from the flow is a function of Π 2 only. For low values of Π 1 , the power extracted is still a strong function of Π 2 , but is also a weak function of Π 1. For all the cases tested, the power extracted was independent of the value of m n. These results are then compared to results of direct numerical simulations. It is found that Π 1 has a much stronger impact on the power extracted than predicted by the quasi-steady state model. The error is shown to be an inverse function of Π 1. The failure of the quasi-steady state model at low Π 1 is hypothesised to be due to the stronger influence of vortex shedding, which is not accounted for in the quasi-steady model. Spectral analysis of the DNS cases at low Π 1 shows a significant response at the vortex shedding frequency. The strength of the vortex shedding response is also shown to be an inverse function of Π 1. Even though the quasi-steady state model does not accurately predict the power extracted, it does predict the parameter values at which maximum power transfer occurs reasonably well, and both the quasi-steady model and the direct numerical simulations show that this value is basically independent of Π 1 .

This in-water experimental study deals with the effects of the after-body on the FIV response of round and sharp edge cylinders. Different circular, square, diamond, and right-angle isosceles triangular crosssections are investigated. The triangular cylinder is examined in four different symmetrical and unsymmetrical configurations with respect to the incident flow. The current towing tank experiments form a basis for the feasibility study of the isosceles triangular cylinders for FIV energy converters. The results indicate that the cylinders with a flat side perpendicular to the flow have a galloping type of response. In contrast, the cylinders with a sharp vertex pointing the flow show a VIV type of response. The galloping amplitude in the triangular cylinder with similar after-body and separation points to a diamond cylinder is significantly higher than that in the square cylinder. This right isosceles triangular cylinder also displays considerably greater hydroelastic efficiency than other sharp edge oscillators.

This research handles the problem of noise pollution caused by the stone cutting processes in the medium and small factories located close to the populated areas. Noise can be reduced by two main ways: the first method is done by adding sound absorbers to the workshop surrounding walls; the second technique is by building a barrier wall in front of the open facade of the factory. This paper introduces three techniques to reduce the vibration in the stone cutting machine knowing that vibration is the main source of noise, the techniques are: inserting a passive elastomeric rubber pad, designing an active controller based on Integral Force Feedback (IFF), and designing a regulator based on Linear Quadratic Regulator (LQR) for active control of vibrations. Simulation results show the ability of these techniques to regulate the vibrations at various levels.

This study aims to review flow-induced vibration one of the repercussions of vibrations is caused by fluid movement. In general, the investigation of the structure of the systems affects the efficiency of the components that construct those systems. This review examined the influence of generated vibrations and internal pressure on fluid transport pipes using theoretical calculations, practical tests, and numerical analysis to identify and test the dynamic behavior of static fluid transport pipes. The experimental study considered the natural frequencies caused by the fluid pressure effect under various stability situations. The flow of all liquids, such as oil, water, gas, air, and vapors, through the pipes, was tested, and the mathematical models were correctly adjusted. All empirical, theoretical, numerical, and analytical research agrees that several approaches exist to develop, modify, and improve these metrics. However, one factor affecting rheological measurements is vibratio...

Wake-induced vibration (WIV) of a two-degree-of-freedom (2-DOF) downstream square cylinder behind a stationary equal-size upstream square cylinder is numerically investigated at low Reynolds numbers by using Characteristics-Based Split (CBS) finite element algorithm. Due to the interference between the cylinders, the flow pattern and dynamic characteristics of become more complex than an isolated cylinder case. The spacing ratio of the two equal-sized square cylinders in the tandem arrangement is fixed as L/D=5.0. The Reynolds numbers of this two-cylinder system have five types, varying between 40~200 with a unit step of △Re=40. The reduced mass of the square cylinder is M r =2.0, while its reduced velocity changes between U r =3.0~18.0. The numerical results show that the reduced velocity and Reynolds number can affect the characteristics of the flow patterns, oscillatory frequency, maximum amplitudes, and X-Y trajectories of the downstream square cylinder. The predominant vortex shedding patterns are 2S, 2S*, 2P, P+S, 2T and steady mode. Additionally, the figure "8" and figure "dual-8" are observed in the X-Y vibrating trajectories of the downstream square cylinder. Finally, the interactions between cylinders underlying the vibration characteristics of the square cylinder behind a stationary square cylinder with different Reynolds numbers are revealed.

Zusammenfassung Das in diesem Artikel beschriebene Auswerteverfahren ermöglicht für Particle Image Velocimetry (PIV) Messysteme mit geringen Messraten die zeitlich aufgelöste Darstellung hochfrequenter, instationärer Strömungseffekte. Das Verfahren bestimmt die Phasenlage des Phänomens mittels Wavelet-Transformation für jede PIV-Messung. Die Messungen können entsprechend der Phasenlage geordnet und somit die zeitliche Entwicklung des Phänomens über eine Periode dargestellt werden. Die Methode wird anhand des instationären Phänomens der Kármánschen Wirbelstraße auf seine Funktionsfähigkeit überprüft. Summary The method presented enables a Particel Image Velocity (PIV) system with moderate sampling rates to achieve the time-resolved presentation of instationary phenomena with high frequencies. Therefore the method determines the phasing of the phenomena via wavelet transform for each PIV-measurement. The measurements can be arranged according to their phasing and represent the development of the phenomena over one periode in time. The method is tested for the phenomenon of the Kármán vortex street.

In this work, a hybrid numerical approach to predict the vibrational responses of planar structures excited by a turbulent boundary layer is presented. The approach combines an uncorrelated wall plane wave technique with the finite element method. The wall pressure field induced by a turbulent boundary layer is obtained as a set of uncorrelated wall pressure plane waves. The amplitude of these plane waves are determined from the cross spectrum density function of the wall pressure field given either by empirical models from literature or from experimental data. The response of the planar structure subject to a turbulent boundary layer excitation is then obtained from an ensemble average of the different realizations. The numerical technique is computationally efficient as it rapidly converges using a small number of realizations. To demonstrate the method, the vibrational responses of two panels with simply supported or clamped boundary conditions and excited by turbulent flow are considered. In the case study comprising a plate with

The demand for customized small-scale unmanned air such platforms in Taylor and Thomas Cord (2003), Green and span from zero to substantially high advance ratios. In an et al. prop-stream effects over the broader range of advance ratios Stone (2002) comprises numerical modeling and is based on superimposition of prop-stream in numerical panel methods. The prop-stream effects for the small/mini UAV have d/b) is relatively that the diameter of the propeller is often comparable to the

This research delves into the complex dynamics of high-pressure, hot, and dynamic liquids flowing through piping systems. To better understand the various factors that affect the torsional vibration of these liquids, the study uses a coupled nonlinear partial differential equation to analyze generating variables such as fluid flow heat flux, mass ratio, pipe thickness, internal pressurization, vertical motion, longitudinal direction kinetic energy of the inner fluid, and crosssectional area change. The ANSYS CFD R2022a software is used to simulate the model, and a threedimensional model is used to investigate the dynamic behavior of the thin pipe. The numerical modal analysis is performed in the configuration of fluid-structure interaction, and the study also examines the vibratory behavior of the fluid-conveying pipe. The results indicate that the velocity was 7.5% lower in the pipe with plaque model than in the normal pipe model, while pressure and WSS were 94.9% and 74.41% higher, respectively. The study also conducts parametric studies on the effect of temperature, pressure drop, and velocity change on the frequencies. Additionally, the research suggests that a gas column input signal exists in the pipe, which can cause severe vibration when it comes into contact with unreasonable vibration. This study highlights the importance of determining the ideal design for pipes to restore their usual functions and avoid excessive vibration."

Stabilized space-time finite element technique is utilized to perform numerical simulation on the wake-inducedvibrations of two identical tandem circular cylinders placed in the flow at Reynolds number 100. Cylinders are separated by a center to center distance of 5 times the diameter of the cylinder. Results are computed for various values of reduced velocities (1 to 8). The downstream cylinder, of mass ratio 10, is allowed to execute oscillations in both in-line and transverse directions, whereas the upstream cylinder is stationary. Response curve of downstream cylinder is observed to be composed of initial and lower branches. Phenomenon of lock-in is identified at a reduced velocity of 5. Nature of flow exhibits periodicity for the entire range of initial branch with single dominant lift frequency. For reduced velocity near the end of lock-in,flow and body motion shows quasi-periodic behavior with complicated non-overlapping loops in the cylinder trajectory as well as in the phase plots of drag and lift coefficients.

Flow in a branched channel is studied experimentally using the PIV technique. The presented study is concentrated on clarifying the dynamical behaviour in individual branches. The 11 branches issuing from the main channel perpendicularly, all channels are of rectangular cross-section. First, the time-mean flow-field is shown, then the flow dynamics is investigated using the OPD method. Flow patterns and frequencies are evaluated in three selected branches. The separated flow in branches exhibits highly dynamical behaviour, which differs substantially in the branches close to the inflow, in the main channel middle and close to its end. The typical topologies and frequencies of the detected quasi-periodical structures in the channel braches are shown in the study. Mostly, the flow-fields are populated by trains of vortices with alternating orientation and saddle-like structures. The flow-field close to the channel walls affects heat transfer process between the wall and fluid.

Although Particle Image Velocimetry techniques are widely used in the experimental investigation of the flow structure around obstacles, the application of these techniques in wind tunnels is frequently limited by the dimension of the areas involved, which make the image acquisition setup expensive. This paper examines the use of Particle Streak Velocimetry (PSV) and marker detection techniques to measure the flow field around bodies with relatively large dimensions. In spite of its minimal requirements in terms of acquisition setup , the method permits the investigation of complex phenomena. The tests described in the paper were carried out in air using a rigid cylinder, free to oscillate in a wind tunnel. Coupling PSV and marker detection techniques with the phase average of the measured velocity fields, the evolution of vortex shedding behind a cylinder with a diameter of 200 mm was measured with an acquisition area of about 1000 × 1200 mm.

The critical effect of the windward interior angles of elastically mounted trapezoidal bodies on a galloping instability is numerically investigated in this paper using two methodologies of high-fidelity computational fluid dynamics simulations and data-driven stability analysis using the eigensystem realization algorithm. A micro exploration of the dynamical response is processed to understand the mechanism underpinning the structural amplification at the initial stage of the galloping instability and the competition between wake and structural modes. It is observed that very small changes in the windward interior angle of an isosceles-trapezoidal body can provoke or suppress galloping – indeed, a small decrease or increase (low to $1^\circ$ ) of the windward interior angle from a right angle ( $90^\circ$ ) can result in a significant enhancement and complete suppression, respectively, of the galloping oscillations. This supports our hypothesis that the contraction and/or expansion...

The theoretical analysis of coupled-mode self-excited vibration of hydraulic gates is developed in the present paper. The theory is applied to the 87-ton Tainter gate at the Folsom Dam, which according to eyewitness testimony, experienced flow-induced vibrations and failed in l995. In its original design, the Folsom Tainter gate possessed two significant vibration modes. One mode was a whole gate rotation around the trunnion pin, while the second mode was a streamwise bending vibration of the skinplate. For certain upstream water levels, these two modes can couple with each other through hydrodynamic forces and inertia torques, producing self-excited vibration. The equations of motion for the small amplitude coupled-mode vibration are derived in non-dimensional form, revealing the non-dimensional parameters governing the vibrations and the hydrodynamic forces. The characteristics of this coupled-mode self-excited vibration are obtained through approximate numerical solutions, derived by iterative numerical calculations of the equations of motion. In addition, examination and physical explanations for vibration trajectories and energy transfer from the fluid motion to the gate vibration are presented. The theory, along with measured in-air frequencies, mode shapes and damping ratios, is used to generate stability diagrams of the original Folsom gate design.

Flow-induced vibration (FIV) at the spacer grid in the fuel assembly of a Light Water Reactor (LWR) is the leading cause of fuel failure. This project aims to produce a simulation benchmark on the experimental campaign at MACE on axial FIV of a cantilever beam in an annular tube, that mimics the configuration and environment of a typical LWR. The nuclear fuel rod, which consists of fuel pellets filled in Zirconium alloy cladding is modelled in the experiment as a steel rod filled with lead shots that closely approximates the filling density of the fuel pellet. To reduce the complexity and increase the efficiency of the simulation, further simplification is applied by on the geometry and assuming the solid domain as a single material instead of multiple materials. The first mode of frequency of the rod vibrating in quiescent water, which had been validated via the Euler-Bernoulli beam theory against experimental measurements, was used to design the single-material solid domain. Two models were proposed, firstly a solid rod with lower density and stiffness (SLE), and secondly an empty cladding with high density and low stiffness (EHD). Both solid and fluid domains were discretised using the cell-centred finite volume (FV) method and coupled with strong two-way fluid-structure interaction (FSI). Results on the frequency of vibration in quiescent water and in axial flow showed good agreement with experimental measurement, and the computational efficiency is analyzed for different rod models and changes in parameters of the solid domains.

Forced vibration has been experimentally investigated on a model consists of circular pipe with1.6m length. The pipe built in tank (1.2m length, 0.6m height and 0.6m width) horizontally at 0.4m height with two different diameters d=15mm and d=35mm. The pipe conveying laminar flow in the fully developed region, of Reynolds number equals 2000. The experimental results of span pipe conveying water at five stations of forced excitation vibration were studied. The harmonic forced vibration with two different excitation frequencies (10 Hz and 15 Hz) are imposed at all of the five locations. The distance between two stations is (0.2m). Two conditions of pipe environment have been applied, the first in air and the other was immersed in water. It is concluded that the effect of flow induced vibration due to the pipe conveying fluid increases the maximum deflection when the fluid speed increases. The water surrounds the pipes reduce the effect of excitation vibration about (33 – 46%). The eff...

Slender cylinders close together may be exited to self-sustained oscillations which are associated with a hysteretic flow switching in the gap between the two cylinders. Measurements have shown that this flow switching appears with a time resp. phase lag, so that energy can transfer from the flow to the structure. In this study new model tests have been done to determine the flow direction 13k where the flow switching occurs. This has been done by flow visualisation technique with a milk probe in a water channel. It was found that for a forced oscillation 13k is a function of the reduced velocity un. Comparisons with the quasi-static values 13k, t lead to the phase lag A~ of the flow switching. Together with quasi-static force coefficients cL measured in former investigations these data have been used as a basis for calculations of forcedisplacement diagrams which describe the energy input into the oscillating cylinder.

The nonlinear characteristics of the flow-induced vibration of an elastically-supported cylinder-plate assembly are investigated using numerical simulations of the flow past the assembly at a low-Reynolds number Re = 100. The beating phenomenon in the time series of the transverse (lift) force coefficient for both vortex-induced vibration and galloping is studied. The dynamical characteristics of the beating are elucidated using local attributes (local frequency), global attributes (periodicity and symmetry), and the properties of the energy transfer (per unit time) between the cylinder-plate assembly and the surrounding fluid. From this analysis, five distinct types of beating for a cylinder-plate assembly are identified. The nonlinear dynamical characteristics is investigated using a number of methodologies such as the power spectral density, the phase-plane portrait and the Poincaré section. The analysis implies the existence of a close relationship between the multiple characteristic frequencies in the power spectrum and the beating observed in the time variations. Three types of nonlinear oscillations in a cylinder-plate assembly have been identified and characterized in terms of the nature of their limit cycles in the phase plane and the point set distribution in the Poincaré section. The wake mode of a cylinder-plate assembly during beating is found to be invariably asymmetric with highly irregular vortex shapes, e.g., a right-angled vortex designated as S A and a crescent-shaped vortex designated as S B-multiplets (groups) of vortices involving either S A or S B with two elliptically-shaped vortices are closely associated with the observed beating.

The critical effect of the windward interior angles of elastically mounted trapezoidal bodies on a galloping instability is numerically investigated in this paper using two methodologies of high-fidelity computational fluid dynamics simulations and data-driven stability analysis using the eigensystem realization algorithm. A micro exploration of the
dynamical response is processed to understand the mechanism underpinning the structural amplification at the initial stage of the galloping instability and the competition between wake and structural modes. It is observed that very small changes in the windward interior
angle of an isosceles-trapezoidal body can provoke or suppress galloping – indeed, a small decrease or increase (low to 1◦) of the windward interior angle from a right angle (90◦) can result in a significant enhancement and complete suppression, respectively, of the galloping oscillations. This supports our hypothesis that the contraction and/or expansion (viz., fore-aft tapering and/or widening) of the cross-section in the streamline direction has potential influences on galloping triggering from the geometrical perspective. The data-driven stability analysis is also applied to verify and analyse this phenomenon from the perspective of modal analysis. The experimental measurements are also conducted in the wind tunnel to support this hypothesis.

Forced vibration has been experimentally investigated on a model consists of circular pipe with1.6m length. The pipe built in tank (1.2m length, 0.6m height and 0.6m width) horizontally at 0.4m height with two different diameters d=15mm and d=35mm. The pipe conveying laminar flow in the fully developed region, of Reynolds number equals 2000. The experimental results of span pipe conveying water at five stations of forced excitation vibration were studied. The harmonic forced vibration with two different excitation frequencies (10 Hz and 15 Hz) are imposed at all of the five locations. The distance between two stations is (0.2m). Two conditions of pipe environment have been applied, the first in air and the other was immersed in water. It is concluded that the effect of flow induced vibration due to the pipe conveying fluid increases the maximum deflection when the fluid speed increases. The water surrounds the pipes reduce the effect of excitation vibration about (33-46%). The effect difference between the excitation frequencies was about (4-7%).

This study aims to review flow-induced vibration one of the repercussions of vibrations is caused by fluid movement. In general, the investigation of the structure of the systems affects the efficiency of the components that construct those systems. This review examined the influence of generated vibrations and internal pressure on fluid transport pipes using theoretical calculations, practical tests, and numerical analysis to identify and test the dynamic behavior of static fluid transport pipes. The experimental study considered the natural frequencies caused by the fluid pressure effect under various stability situations. The flow of all liquids, such as oil, water, gas, air, and vapors, through the pipes, was tested, and the mathematical models were correctly adjusted. All empirical, theoretical, numerical, and analytical research agrees that several approaches exist to develop, modify, and improve these metrics. However, one factor affecting rheological measurements is vibration, which was addressed as needed in the middle of the 20th century due to major discoveries that damage could be rooted in vibration. Established on the determinations, they provided mathematical models paired with pressure and velocity measurements of moving fluids and the influence of produced or uninduced vibration. This study demonstrates that additional empirical investigations, particularly more detailed analytical methodologies, are urgently required to produce better findings.

One of the effects of vibrations resulting from the flow of fluids is the failure that occurs to the structure of the systems, which in turn affects the efficiency of the parts that make up those systems. for the purpose of studying the possibility of improving the performance of the systems, a liquid other than water and coolant (super antifriz\petrol ofisi) was chosen because of its advantages that can be taken advantage of, including the high viscosity of water and its tolerance to high temperatures resulting from combustion or air temperature, as well as low temperatures to ensure the operation of the system, that is, it maintains stability system temperature to obtain the best possible condition In addition to the purity of the liquid from salts and the presence of a percentage of oil in the composition of the coolant, an insulating layer is formed inside the pipes to prevent rust and corrosion in the pipes, thus ensuring the flow of fluids and prolonging the life of the pipes. The aim is to study and analyze the effect of induced vibrations and internal pressure on fluid transport pipes, and to compare them in the cases of using water and coolant under the same conditions. An empirical analysis considering the natural frequencies produced by the effect of fluid pressure under various stabilization conditions. It was observed from the results that the higher the pressure, the greater the percentage of the deflection of the copper tubes compared to the Aluminium tubes when using both liquids (water and coolant) at the same boundary condition noted the percentage of the deflection difference when using copper pipe (from 0% to 20.3%) was less than using Aluminium (from 2% to 59%) when the pressure was increased. That mean the Aluminium pipe better than copper pipe.

The utilization of biomass for heat and power generation has aroused the interest of most researchers especially those of energy .In converting solid fuel to a usable form of energy,pyrolysis plays an integral role. Understanding this very important phenomenon in the thermochemical conversion processes and representing it with appropriate mathematical models is vital in the design of pyrolysis reactors and biomass gasifiers. Therefore, this study presents analytical solutions to the kinetic and the heat transfer equations that describe the slow pyrolysis of a biomass particle. The effects of Biot number, temperature and residence time on biomass particle decomposition were studied. The results from the proposed analytical models are in good agreement with the reported experimental results. The developed analytical solutions to the heat transfer equations which have been stated to be “analytically involved” showed average percentageerror and standard deviations 0.439 and 0.103 from t...

The need for energy and its utilization for industrial, household purposes has seen an ever increasing hike. However, the uncontrolled and excessive usage of conventional energy resources, like burning fossil fuels has been deteriorating the environment and thereby causing health related issues. Flat-plate solar collector is one of the most promising system to utilize solar energy to fulfil the thermal or heating requirements. An effective design of a flatplate solar collector requires numerous factors to be considered such as riser tube material and its configuration, absorber plate material, glazing material etc. In the present work, the scope of the study is to analyse the effect of glazing material on the thermal and hydraulic performance of the collector. For this purpose, five different types of materials have been selected in a typical generalized computer-aided module of a riser configuration for a flat-plate solar collector and each material has been examined for its performance with different mass flow rates of working fluids. Computational fluid dynamics (CFD) has been instrumental in studying the influence of the glazing materials.

In this present investigation, textiles samples of non-polymeric nature, e.g, cotton, silk etc. of Indian origin were pyrolysed in a 50 mm diameter and 640 mm long packed bed pyrolyser placed in a tubular furnace from 573K to 1173K in a nitrogen atmosphere. Experiments were designed to investigate the effects of temperature of pyrolysis on yields of char, pyro-oil and gas and their characteristics. A kinetic scheme has been proposed where two parallel reactions occur simultaneously to produce volatiles and char. The kinetic rate constants of both the reactions have been determined in the temperature range under study. The activation energies and pre-exponential factors of all products (solid reactant, volatile and char) have been determined. A mathematical model for the pyrolysis of textile waste has been developed using the kinetic parameters determined under the present study. Calorific values of pyro-oil and char obtained at different temperature have been determined. The structu...

The transverse flow-induced vibration of an elastically supported cylinder-plate assembly (viz., a rigid splitter-plate attached to the downstream side of a circular cylinder) with a low mass ratio of 10 and a zero structural damping coefficient at a Reynolds number of 100 is investigated in the present work. A careful identification of all the branches in the amplitude response of an assembly with various plate lengths is undertaken, in conjunction with the associated flow dynamics responsible for these branches involving various aspects of the flow, such as the vortex-shedding in the far wake and the evolution of the shear layers generated on the upper and lower surfaces of the cylinder in the near wake. This knowledge offers crucial new perspectives on the nature and physical mechanisms behind the complex dynamics of a cylinder-plate system. These investigations involve a wide range of plate lengths L SP =D ¼ 0-4 (where D is the diameter of the circular cylinder) over an extensive span of reduced velocities U r ¼ 2-30. For L SP =D 0:5, a self-limiting oscillation is induced in the structure-this can be either a vortex-induced vibration (VIV) or an integrated VIV-galloping response. For L SP =D ! 0:75, the amplitude response is nonlimited in the sense that the amplitude increases linearly with increasing U r. More precisely, the amplitude response consists of either a strongly correlated VIV-galloping regime (at L SP =D ¼ 0:75) or two clearly separated regimes of VIV and galloping (for L SP =D > 0:75). In the galloping regime, both odd-and even-multiple synchronizations between the system oscillation and the vortex shedding are supported. "Kinks" in the amplitude response signal the onset of synchronization branches in the galloping regime. Two new branches have been identified for a cylinder-plate assembly with longer plate lengths, namely, an initial galloping branch and a still (quiescent) branch. The initial galloping branch is associated with wake meandering. For the still branch, the assembly is stationary (no vibratory motion), and flow over the assembly is steady (no vortex shedding or shear-layer meandering).

The need for energy and its utilization for industrial, household purposes has seen an ever increasing hike. However, the uncontrolled and excessive usage of conventional energy resources, like burning fossil fuels has been deteriorating the environment and thereby causing health related issues. Flat-plate solar collector is one of the most promising system to utilize solar energy to fulfil the thermal or heating requirements. An effective design of a flatplate solar collector requires numerous factors to be considered such as riser tube material and its configuration, absorber plate material, glazing material etc. In the present work, the scope of the study is to analyse the effect of glazing material on the thermal and hydraulic performance of the collector. For this purpose, five different types of materials have been selected in a typical generalized computer-aided module of a riser configuration for a flat-plate solar collector and each material has been examined for its performance with different mass flow rates of working fluids. Computational fluid dynamics (CFD) has been instrumental in studying the influence of the glazing materials.