scholarly journals Flow-induced vibrations of a rotating cylinder in an arbitrary direction

2018 ◽  
Vol 860 ◽  
pp. 739-766 ◽  
Author(s):  
Rémi Bourguet
Keyword(s):  
Three Dimensional ◽  
Rotating Cylinder ◽  
The Body ◽  
Arbitrary Direction ◽  
Fast Rotation ◽  
Flow Past ◽  
Symmetrical Configuration ◽  
Wide Range ◽  
Flow Induced Vibrations ◽  
The Impact

The flow-induced vibrations of an elastically mounted circular cylinder, free to oscillate in an arbitrary direction and forced to rotate about its axis, are examined via two- and three-dimensional simulations, at a Reynolds number equal to 100, based on the body diameter and inflow velocity. The behaviour of the flow–structure system is investigated over the entire range of vibration directions, defined by the angle $\unicode[STIX]{x1D703}$ between the direction of the current and the direction of motion, a wide range of values of the reduced velocity $U^{\star }$ (inverse of the oscillator natural frequency) and three values of the rotation rate (ratio between the cylinder surface and inflow velocities), $\unicode[STIX]{x1D6FC}\in \{0,1,3\}$, in order to cover the reference non-rotating cylinder case, as well as typical slow and fast rotation cases. The oscillations of the non-rotating cylinder ($\unicode[STIX]{x1D6FC}=0$) develop under wake-body synchronization or lock-in, and their amplitude exhibits a bell-shaped evolution, typical of vortex-induced vibrations (VIV), as a function of $U^{\star }$. When $\unicode[STIX]{x1D703}$ is increased from $0^{\circ }$ to $90^{\circ }$ (or decreased from $180^{\circ }$ to $90^{\circ }$), the bell-shaped curve tends to monotonically increase in width and magnitude. For all angles, the flow past the non-rotating body is two-dimensional with formation of two counter-rotating spanwise vortices per cycle. The behaviour of the system remains globally the same for $\unicode[STIX]{x1D6FC}=1$. The principal effects of the slow rotation are a slight amplification of the VIV-like responses and widening of the vibration windows, as well as a limited asymmetry of the responses and forces about the symmetrical configuration $\unicode[STIX]{x1D703}=90^{\circ }$. The impact of the fast rotation ($\unicode[STIX]{x1D6FC}=3$) is more pronounced: VIV-like responses persist over a range of $\unicode[STIX]{x1D703}$ but, outside this range, the system is found to undergo a transition towards galloping-like oscillations characterised by amplitudes growing unboundedly with $U^{\star }$. A quasi-steady modelling of fluid forcing predicts the emergence of galloping-like responses as $\unicode[STIX]{x1D703}$ is varied, which suggests that they could be mainly driven by the mean flow. It, however, appears that flow unsteadiness and body motion remain synchronised in this vibration regime where a variety of multi-vortex wake patterns are uncovered. The interaction with flow dynamics results in deviations from the quasi-steady prediction. The successive steps in the evolution of the vibration amplitude versus $U^{\star }$, linked to wake pattern switch, are not captured by the quasi-steady approach. The flow past the rapidly-rotating, vibrating cylinder becomes three-dimensional over an interval of $\unicode[STIX]{x1D703}$ including the in-line oscillation configuration, with only a minor effect on the system behaviour.

scholarly journals In-line flow-induced vibrations of a rotating cylinder

2015 ◽  
Vol 781 ◽  
pp. 127-165 ◽  
Author(s):  
Rémi Bourguet ◽  
David Lo Jacono
Keyword(s):  
Rotation Rate ◽  
Vibration Amplitude ◽  
Three Dimensional ◽  
Low Frequency ◽  
Rotating Cylinder ◽  
The Body ◽  
Cylinder Surface ◽  
Force Frequency ◽  
Direction Parallel ◽  
Flow Induced Vibrations

The flow-induced vibrations of an elastically mounted circular cylinder, free to oscillate in the direction parallel to the current and subjected to a forced rotation about its axis, are investigated by means of two- and three-dimensional numerical simulations, at a Reynolds number equal to 100 based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to 2 (first vibration region), then the body and the flow are steady until a rotation rate close to 2.7 where a second vibration region begins. Each vibration region is characterized by a specific regime of response. In the first region, the vibration amplitude follows a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency). The maximum vibration amplitudes, even though considerably augmented by the rotation relative to the non-rotating body case, remain lower than 0.1 cylinder diameters. Due to their trends as functions of the reduced velocity and to the fact that they develop under a condition of wake-body synchronization or lock-in, the responses of the rotating cylinder in this region are comparable to the vortex-induced vibrations previously described in the absence of rotation. The symmetry breaking due to the rotation is shown to directly impact the structure displacement and fluid force frequency contents. In the second region, the vibration amplitude tends to increase unboundedly with the reduced velocity. It may become very large, higher than 2.5 diameters in the parameter space under study. Such structural oscillations resemble the galloping responses reported for non-axisymmetric bodies. They are accompanied by a dramatic amplification of the fluid forces compared to the non-vibrating cylinder case. It is shown that body oscillation and flow unsteadiness remain synchronized and that a variety of wake topologies may be encountered in this vibration region. The low-frequency, large-amplitude responses are associated with novel asymmetric multi-vortex patterns, combining a pair and a triplet or a quartet of vortices per cycle. The flow is found to undergo three-dimensional transition in the second vibration region, with a limited influence on the system behaviour. It appears that the transition occurs for a substantially lower rotation rate than for a rigidly mounted cylinder.

scholarly journals Drops bouncing off macro-textured superhydrophobic surfaces

2017 ◽  
Vol 824 ◽  
pp. 866-885 ◽  
Author(s):  
Ali Mazloomi Moqaddam ◽  
Shyam S. Chikatamarla ◽  
Iliya V. Karlin
Keyword(s):  
Contact Time ◽  
Numerical Study ◽  
Three Dimensional ◽  
Superhydrophobic Surfaces ◽  
Nonlinear Behaviour ◽  
Textured Surfaces ◽  
Texture Density ◽  
Wide Range ◽  
Quantitative Manner ◽  
The Impact

Recent experiments with droplets impacting macro-textured superhydrophobic surfaces revealed new regimes of bouncing with a remarkable reduction of the contact time. Here we present a comprehensive numerical study that reveals the physics behind these new bouncing regimes and quantifies the roles played by various external and internal forces. For the first time, accurate three-dimensional simulations involving realistic macro-textured surfaces are performed. After demonstrating that simulations reproduce experiments in a quantitative manner, the study is focused on analysing the flow situations beyond current experiments. We show that the experimentally observed reduction of contact time extends to higher Weber numbers, and analyse the role played by the texture density. Moreover, we report a nonlinear behaviour of the contact time with the increase of the Weber number for imperfectly coated textures, and study the impact on tilted surfaces in a wide range of Weber numbers. Finally, we present novel energy analysis techniques that elaborate and quantify the interplay between the kinetic and surface energy, and the role played by the dissipation for various Weber numbers.

scholarly journals Hyaluronan and the Fascial Frontier

2021 ◽  
Vol 22 (13) ◽  
pp. 6845
Author(s):  
Rebecca L. Pratt
Keyword(s):  
Nerve Fibers ◽  
The Body ◽  
Water Volume ◽  
Cell Behavior ◽  
Connective Tissues ◽  
Wide Range ◽  
The World ◽  
Extracellular Microenvironment ◽  
The Impact ◽  
The Relationship

The buzz about hyaluronan (HA) is real. Whether found in face cream to increase water volume loss and viscoelasticity or injected into the knee to restore the properties of synovial fluid, the impact of HA can be recognized in many disciplines from dermatology to orthopedics. HA is the most abundant polysaccharide of the extracellular matrix of connective tissues. HA can impact cell behavior in specific ways by binding cellular HA receptors, which can influence signals that facilitate cell survival, proliferation, adhesion, as well as migration. Characteristics of HA, such as its abundance in a variety of tissues and its responsiveness to chemical, mechanical and hormonal modifications, has made HA an attractive molecule for a wide range of applications. Despite being discovered over 80 years ago, its properties within the world of fascia have only recently received attention. Our fascial system penetrates and envelopes all organs, muscles, bones and nerve fibers, providing the body with a functional structure and an environment that enables all bodily systems to operate in an integrated manner. Recognized interactions between cells and their HA-rich extracellular microenvironment support the importance of studying the relationship between HA and the body’s fascial system. From fasciacytes to chronic pain, this review aims to highlight the connections between HA and fascial health.

scholarly journals The true cost of in-patient obesity: impact of obesity on inflammatory stress and morbidity

2010 ◽  
Vol 69 (4) ◽  
pp. 511-517 ◽  
Author(s):  
Robert F. Grimble
Keyword(s):  
Inflammatory Cytokines ◽  
Inflammatory Cytokine ◽  
Cytokine Production ◽  
The Body ◽  
Morbidity And Mortality ◽  
Metabolic Effects ◽  
Inflammatory Cytokine Production ◽  
Inflammatory Stress ◽  
Wide Range ◽  
The Impact

The objective of the present review is to provide an overview of the metabolic effects of pro-inflammatory cytokine production during infection and injury; to highlight the disadvantages of pro-inflammatory cytokine production and inflammatory stress on morbidity and mortality of patients; to identify the influence of genetics and adiposity on inflammatory stress in patients and to indicate how nutrients may modulate the inflammatory response in patients. Recent research has shown clearly that adipose tissue actively secretes a wide range of pro- and anti-inflammatory cytokines. Paradoxically, although inflammation is an essential part of the response of the body to infection, surgery and trauma, it can adversely affect patient outcome. The metabolic effects of inflammation are mediated by pro-inflammatory cytokines. Metabolic effects include insulin insensitivity, hyperlipidaemia, muscle protein loss and oxidant stress. These effects, as well as being present during infective disease, are also present in diseases with a covert inflammatory basis. These latter diseases include obesity and type 2 diabetes mellitus. Inflammatory stress also increases during aging. The level of cytokine production, within individuals, is influenced by single nucleotide polymorphisms (SNP) in cytokine genes. The combination of SNP controls the relative level of inflammatory stress in both overt and covert inflammatory diseases. The impact of cytokine genotype on the intensity of inflammatory stress derived from an obese state is unknown. While studies remain to be done in the latter context, evidence shows that these genomic characteristics influence morbidity and mortality in infectious disease and diseases with an underlying inflammatory basis and thereby influence the cost of in-patient obesity. Antioxidants andn-3 PUFA alter the intensity of the inflammatory process. Recent studies show that genotypic factors influence the effectiveness of immunonutrients. A better understanding of this aspect of nutrient–gene interactions and of the genomic factors that influence the intensity of inflammation during disease will help in the more effective targeting of nutritional therapy.

scholarly journals Flow-induced vibrations of a rotating cylinder

2014 ◽  
Vol 740 ◽  
pp. 342-380 ◽  
Author(s):  
Rémi Bourguet ◽  
David Lo Jacono
Keyword(s):  
Symmetry Breaking ◽  
Flow Direction ◽  
Cross Flow ◽  
Maximum Amplitude ◽  
Rotating Cylinder ◽  
Free Vibrations ◽  
Cylinder Surface ◽  
Single Vortex ◽  
Flow Induced Vibrations ◽  
The Impact

AbstractThe flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to $100$, based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate freely up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to $4$. Under forced rotation, the vibration amplitude exhibits a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency) and reaches $1.9$ diameters, i.e. three times the maximum amplitude in the non-rotating case. The free vibrations of the rotating cylinder occur under a condition of wake–body synchronization similar to the lock-in condition driving non-rotating cylinder VIV. The largest vibration amplitudes are associated with a novel asymmetric wake pattern composed of a triplet of vortices and a single vortex shed per cycle, the ${\rm T} + {\rm S}$ pattern. In the low-frequency vibration regime, the flow exhibits another new topology, the U pattern, characterized by a transverse undulation of the spanwise vorticity layers without vortex detachment; consequently, free oscillations of the rotating cylinder may also develop in the absence of vortex shedding. The symmetry breaking due to the rotation is shown to directly impact the selection of the higher harmonics appearing in the fluid force spectra. The rotation also influences the mechanism of phasing between the force and the structural response.

scholarly journals Assessment of Machine-Learned Turbulence Models Trained for Improved Wake-Mixing in Low-Pressure Turbine Flows

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8327
Author(s):  
Roberto Pacciani ◽  
Michele Marconcini ◽  
Francesco Bertini ◽  
Simone Rosa Taddei ◽  
Ennio Spano ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Computational Domain ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Turbulence Closures ◽  
The Impact

This paper presents an assessment of machine-learned turbulence closures, trained for improving wake-mixing prediction, in the context of LPT flows. To this end, a three-dimensional cascade of industrial relevance, representative of modern LPT bladings, was analyzed, using a state-of-the-art RANS approach, over a wide range of Reynolds numbers. To ensure that the wake originates from correctly reproduced blade boundary-layers, preliminary analyses were carried out to check for the impact of transition closures, and the best-performing numerical setup was identified. Two different machine-learned closures were considered. They were applied in a prescribed region downstream of the blade trailing edge, excluding the endwall boundary layers. A sensitivity analysis to the distance from the trailing edge at which they are activated is presented in order to assess their applicability to the whole wake affected portion of the computational domain and outside the training region. It is shown how the best-performing closure can provide results in very good agreement with the experimental data in terms of wake loss profiles, with substantial improvements relative to traditional turbulence models. The discussed analysis also provides guidelines for defining an automated zonal application of turbulence closures trained for wake-mixing predictions.

scholarly journals On the Impact of Climate Change on Building Energy Consumptions: A Meta-Analysis

Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 354
Author(s):  
Ludovica Maria Campagna ◽  
Francesco Fiorito
Keyword(s):  
Climate Change ◽  
Energy Consumption ◽  
Climate Change Impacts ◽  
Building Energy ◽  
The Body ◽  
Building Energy Consumption ◽  
Adaptation Measures ◽  
Climate Zones ◽  
Wide Range ◽  
The Impact

The body of literature on climate change impacts on building energy consumption is rising, driven by the urgency to implement adaptation measures. Nevertheless, the multitude of prediction methodologies, future scenarios, as well as climate zones investigated, results in a wide range of expected changes. For these reasons, the present review aims to map climate change impacts on building energy consumption from a quantitative perspective and to identify potential relationships between energy variation and a series of variables that could affect them, including heating and cooling degree-days (HDDs and CDDs), reference period, future time slices and IPCC emission scenarios, by means of statistical techniques. In addition, an overview of the main characteristics of the studies related to locations investigated, building types and methodological approaches are given. To sum up, global warming leads to: (i) decrease in heating consumptions; (ii) increase in cooling consumption; (iii) growth in total consumptions, with notable differences between climate zones. No strong correlation between the parameters was found, although a moderate linear correlation was identified between heating variation and HDDs, and total variation and HDDs. The great variability of the collected data demonstrates the importance of increasing specific impact studies, required to identify appropriate adaptation strategies.

scholarly journals Laminar buffet and flow control

2019 ◽  
Vol 234 (1) ◽  
pp. 124-139 ◽  
Author(s):  
V Brion ◽  
J Dandois ◽  
R Mayer ◽  
P Reijasse ◽  
T Lutz ◽  
...  
Keyword(s):  
Shock Wave ◽  
Separation Bubble ◽  
Control Strategies ◽  
Three Dimensional ◽  
Low Frequency ◽  
Frequency Component ◽  
High Frequency Component ◽  
Mean Flow ◽  
Flow Past ◽  
The Impact

An experimental investigation of the transonic flow past the laminar OALT25 airfoil has been conducted to analyze the impact of laminar flow upon the shock wave dynamics and the existence of a laminar buffet like phenomenon. Tests have been carried out at freestream Mach numbers varying in the range of 0.7–0.8, angle of attack from 0.5° to 4°, and with two tripping configurations at the upper surface of the wing. The (airfoil) chord based Reynolds number is about three million. Results obtained from pressure taps and sensors measurements, as well as Schlieren visualizations of the flow reveal the presence of a laminar buffet phenomenon in sharp contrast with the turbulent phenomenon, as it features a freestream- and chord-based normalized frequency of about unity while turbulent buffet occurs for a frequency close to 0.07 (Jacquin et al., AIAA J 2009; 47). A low-frequency mode, at a frequency of about 0.05 is also present in the laminar situation, notably lower than the high-frequency component. The latter exhibits strong oscillations of the shock foot and vertical wavelike deformations of the shock wave and the former moves the shock back and forth over a small portion of chord, quite similar to the turbulent phenomenon. The mean flow past the laminar wing is characterized by a laminar separation bubble under the shock foot, which likely contributes much to the novel dynamics revealed by the present experiments. Two control strategies of the unsteady shock wave are implemented, one consisting of three-dimensional bumps and one consisting of steady jets blowing transversely to the freestream. It is found that bumps provide a significant reduction of the buffet intensity in the laminar situation. The jets are able to completely remove the flow unsteadiness in both laminar and turbulent conditions.

Model construction of engagement and outcomes in consumers food life

2019 ◽  
Vol 121 (1) ◽  
pp. 218-239 ◽  
Author(s):  
Saman Sheikhesmaeili ◽  
Sana Hazbavi
Keyword(s):  
Customer Satisfaction ◽  
The Body ◽  
Food Marketing ◽  
Sufficient Evidence ◽  
Equation Modeling ◽  
Valuable Insight ◽  
Content Type ◽  
Wide Range ◽  
The Impact ◽  
Customer Satisfaction And Loyalty

Purpose The purpose of this paper is to determine the impact of food-related lifestyle (FRL) and food-related personality traits (FRPTs) on customer satisfaction and loyalty so that sufficient evidence for forming a new pattern of predictors of customer satisfaction and loyalty can be explored. Design/methodology/approach The research method in this study was the descriptive type and was based on the goal of the applied research methods. Data were collected from 384 sample group consumers of chain stores in the city of Tehran. The hypothesized relationships were tested using structural equation modeling (SEM). Findings Final results of study showed the significant effects of FRL and FRPT on satisfaction and loyalty of consumers. This indicates that aforementioned variables can create customer satisfaction and loyalty toward food. The research conceptual model was confirmed with goodness of fit. Research limitations/implications First, the sample consisted of customers who use a wide range of food despite diverse motives and interests. While knowing that costumers’ specific traits about food would have provided a more detailed and comprehensive understanding, conducting research in a set of general food consumer without considering special foods category could be a limitation. Second, and more importantly, since the customer behavior in consumption choices is an unconscious and cognitive process, other factors and domain that are linked to customer satisfaction and loyalty would have been missed. Practical implications This study shows that understanding the behavioral aspects of food consumption can help food producing companies to adjust their production and specially to foresee changes. Marketers are advised to investigate customer traits to promote customer satisfaction and loyalty effectively. This paper contributes to the body of knowledge in food marketing. Originality/value The present study offers a unique and valuable insight into a customer’s behavior and deepens customer satisfaction and loyalty by incorporating FRL, food neophobia scale and food involvement scale as independent variables to contribute knowledge in the context of food marketing, and throws some light upon the predictive power of mentioned variables on customer behaviors.

Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Markus Häfele ◽  
Christoph Traxinger ◽  
Marius Grübel ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Low Pressure ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Cfd Model ◽  
Wide Range ◽  
The Impact

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

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