Hydrodynamic Loads on Flexible Marine Structures due to Vortex Shedding

1982 ◽  
Vol 104 (4) ◽  
pp. 330-336 ◽  
Author(s):  
M. J. Every ◽  
R. King ◽  
O. M. Griffin
Keyword(s):  
Vortex Shedding ◽  
Reduction Method ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Marine Structures ◽  
Flow Induced Vibration ◽  
Hydrodynamic Loads ◽  
Vortex Induced Vibrations ◽  
Air Blowing ◽  
Made In

This paper makes a comparison of experimental measurements and a recently developed methodology for the prediction of the increase in the steady drag of a cylinder undergoing vortex-induced vibrations. The experimental results were obtained during the development of a means to reduce the flow-induced vibration of a cable-suspended pile of the COGNAC platform installation and agree well with the predictions made in this paper. Next, a brief consideration is made of some of the authors’ experience of methods used to reduce vortex-induced vibrations, and hence stress levels. Finally, a reduction method which used an air-blowing manifold is described and results presented.

High-Temperature Dielectric Properties Measurements of Ceramics

1992 ◽  
Vol 269 ◽  
Author(s):  
Shane Bringhurst ◽  
Octavio M. Andrade ◽  
Magdy F. Iskander
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Frequency Band ◽  
Perturbation Technique ◽  
Measurement Techniques ◽  
Coaxial Line ◽  
Experimental Results ◽  
Experimental Measurements ◽  
Insulating Materials ◽  
Made In

ABSTRACTThis paper dicusses experimental arrangements, describes measurement techniques and presents experimental results for hightemperature broadband dielectric properties measurements of ceramics. The cavity perturbation technique and the open-ended coaxial line method are used in these experimental measurements. The design and construction details of cavities and probes are described and representative results of measurements on zirconia and alumina samples (green and sintered) are presented. Results of measurements made on insulating materials are shown. In general measurements are made in the frequency band 1 to 10 GHz and temperatures up to 1000°C.

Experimental Investigation of the Vortex Shedding in the Wake of Oblique and Blunt Trailing Edge Hydrofoils Using PIV-POD Method

2010 ◽  
Author(s):  
Amirreza Zobeiri ◽  
Philippe Ausoni ◽  
Franc¸ois Avellan ◽  
Mohamed Farhat
Keyword(s):  
Experimental Investigation ◽  
Phase Shift ◽  
Vortex Shedding ◽  
High Speed ◽  
Flow Induced Vibration ◽  
Trailing Edge ◽  
Blunt Trailing Edge ◽  
Vortex Induced Vibrations ◽  
Image Velocimetry ◽  
High Reynolds

This paper presents an experimental investigation of the vortex shedding in the wake of blunt and oblique trailing edge hydrofoils at high Reynolds number, Re = 5 105 − 2.9 106. The velocity field in the wake is surveyed with the help of Particle-Image-Velocimetry, PIV, using Proper-Orthogonal-Decomposition, POD. Besides, flow induced vibration measurements and high-speed visualization are performed. The high-speed visualization clearly shows that the oblique trailing edge leads to a spatial phase shift of the upper and lower vortices at their generation stage, resulting their partial cancellation. For the oblique trailing edge geometry and in comparison with the blunt one, the vortex-induced vibrations are significantly reduced. Moreover, PIV data reveals a lower vorticity for the oblique trailing edge. The phase shift between upper and lower vortices, introduced by the oblique truncation of the trailing edge, is found to vanish in the far wake, where alternate shedding is recovered as observed with the blunt trailing edge. The phase shift generated by the oblique trailing edge and the resulting partial cancellation of the vortices is believed to be the main reason of the vibration reduction.

Experimental Measurements in the Acquisition of Biosignals from a Neuronal Cell Culture for an Exoprosthesis Command

2018 ◽  
Vol 69 (10) ◽  
pp. 2948-2939 ◽  
Author(s):  
Carmen Moldovan ◽  
Lidia Dobrescu ◽  
Violeta Ristoiu ◽  
Bogdan Firtat ◽  
Silviu Dinulescu ◽  
...  
Keyword(s):  
Cell Culture ◽  
Glass Plate ◽  
Neuronal Cell ◽  
Cellular Biology ◽  
Experimental Measurements ◽  
Neuron Culture ◽  
Neuronal Cell Culture ◽  
Made In

This article presents experimental measurements performed in order to connect a neuronal cell culture to an exoprosthesis. The experiments focused on the biosignals� acquisition from the cell culture. A special gold-plated glass plate device was realized and several constructive variants were analyzed. A Olympus microscope with fluorescence and photo system was used. The acquisition of bio signals from the neuron culture is realized and described in the paper. The measurements were made in the sterile environment within the laboratory of Institute of Cellular Biology and Pathology. The measurements have been made for the pair of electrodes 1-1 at the edge of the glass plate.

scholarly journals Helical growth during the phototropic response, avoidance response, and in stiff mutants of Phycomyces blakesleeanus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Joseph K. E. Ortega ◽  
Revathi P. Mohan ◽  
Cindy M. Munoz ◽  
Shankar Lalitha Sridhar ◽  
Franck J. Vernerey
Keyword(s):  
Avoidance Response ◽  
Experimental Results ◽  
Sensory Transduction ◽  
Growth Responses ◽  
Phycomyces Blakesleeanus ◽  
Sensory Stimuli ◽  
Phototropic Response ◽  
Biophysical Models ◽  
Helical Growth ◽  
Made In

AbstractThe sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the “fibril reorientation and slippage” hypothesis, global biophysical equations, and local statistical biophysical models are discussed.

scholarly journals Numerical and experimental study of the dynamic factor of the dynamic load on the urban railway

2020 ◽  
Vol 29 (1) ◽  
pp. 195-202
Author(s):  
Tran Anh Dung ◽  
Mai Van Tham ◽  
Do Xuan Quy ◽  
Tran The Truyen ◽  
Pham Van Ky ◽  
...  
Keyword(s):  
Experimental Study ◽  
Dynamic Load ◽  
Dynamic Measurement ◽  
Experimental Results ◽  
Load Factor ◽  
Dynamic Factor ◽  
Experimental Measurements ◽  
Train Speed ◽  
Dynamic Load Factor

AbstractThis paper presents simulation calculations and experimental measurements to determine the dynamic load factor (DLF) of train on the urban railway in Vietnam. Simulation calculations are performed by SIMPACK software. Dynamic measurement experiments were conducted on Cat Linh – Ha Dong line. The simulation and experimental results provide the DLF values with the largest difference of 2.46% when the train speed varies from 0 km/h to 80 km/h

scholarly journals Vortex-induced vibrations of a long flexible cylinder in shear flow

2011 ◽  
Vol 677 ◽  
pp. 342-382 ◽  
Author(s):  
REMI BOURGUET ◽  
GEORGE E. KARNIADAKIS ◽  
MICHAEL S. TRIANTAFYLLOU
Keyword(s):  
Shear Flow ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Maximum Velocity ◽  
Travelling Wave ◽  
Transition To Turbulence ◽  
Wave Component ◽  
Flexible Cylinder ◽  
Vortex Induced Vibrations ◽  
Lock In

We investigate the in-line and cross-flow vortex-induced vibrations of a long cylindrical tensioned beam, with length to diameter ratio L/D = 200, placed within a linearly sheared oncoming flow, using three-dimensional direct numerical simulation. The study is conducted at three Reynolds numbers, from 110 to 1100 based on maximum velocity, so as to include the transition to turbulence in the wake. The selected tension and bending stiffness lead to high-wavenumber vibrations, similar to those encountered in long ocean structures. The resulting vortex-induced vibrations consist of a mixture of standing and travelling wave patterns in both the in-line and cross-flow directions; the travelling wave component is preferentially oriented from high to low velocity regions. The in-line and cross-flow vibrations have a frequency ratio approximately equal to 2. Lock-in, the phenomenon of self-excited vibrations accompanied by synchronization between the vortex shedding and cross-flow vibration frequencies, occurs in the high-velocity region, extending across 30% or more of the beam length. The occurrence of lock-in disrupts the spanwise regularity of the cellular patterns observed in the wake of stationary cylinders in shear flow. The wake exhibits an oblique vortex shedding pattern, inclined in the direction of the travelling wave component of the cylinder vibrations. Vortex splittings occur between spanwise cells of constant vortex shedding frequency. The flow excites the cylinder under the lock-in condition with a preferential in-line versus cross-flow motion phase difference corresponding to counter-clockwise, figure-eight orbits; but it damps cylinder vibrations in the non-lock-in region. Both mono-frequency and multi-frequency responses may be excited. In the case of multi-frequency response and within the lock-in region, the wake can lock in to different frequencies at various spanwise locations; however, lock-in is a locally mono-frequency event, and hence the flow supplies energy to the structure mainly at the local lock-in frequency.

Influence of Trailing-Edge Geometry on Hydraulic-Turbine-Blade Vibration Resulting From Vortex Excitation

1960 ◽  
Vol 82 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Gunnar Heskestad ◽  
D. R. Olberts
Keyword(s):  
Boundary Layer ◽  
Turbine Blade ◽  
Vortex Shedding ◽  
Hydraulic Turbine ◽  
Trailing Edge ◽  
Blade Vibration ◽  
Edge Geometry ◽  
Blade Thickness ◽  
Vortex Induced Vibrations ◽  
Approach Velocity

A study was made to determine effects of trailing-edge geometry on the vortex-induced vibrations of a model blade designed to simulate the conditions at the trailing edge of a hydraulic-turbine blade. For the type of trailing-edge flow encountered, characterized by a thick boundary layer relative to the blade thickness, the vortex-shedding frequency could not be represented by any modification of the Strouhal formula. The amplitude of the induced vibrations increased with the strength of a vortex in the von Karman vortex street of the wake; one exception was provided by a grooved edge, which is discussed in some detail. For a particular approach velocity, the vortex strength is primarily a function of the ratio of distance between separation points to boundary-layer thickness, the degree of “shielding” between regions of vortex growth, and frequency of vortex shedding.

scholarly journals Fractional Wavelet-Based Generative Scattering Networks

2021 ◽  
Vol 15 ◽  
Author(s):  
Jiasong Wu ◽  
Xiang Qiu ◽  
Jing Zhang ◽  
Fuzhi Wu ◽  
Youyong Kong ◽  
...  
Keyword(s):  
Dimensionality Reduction ◽  
Reduction Method ◽  
Gaussian White Noise ◽  
Principal Component ◽  
Experimental Results ◽  
Generative Adversarial Networks ◽  
Image Generation ◽  
Adversarial Networks ◽  
Dimensionality Reduction Method

Generative adversarial networks and variational autoencoders (VAEs) provide impressive image generation from Gaussian white noise, but both are difficult to train, since they need a generator (or encoder) and a discriminator (or decoder) to be trained simultaneously, which can easily lead to unstable training. To solve or alleviate these synchronous training problems of generative adversarial networks (GANs) and VAEs, researchers recently proposed generative scattering networks (GSNs), which use wavelet scattering networks (ScatNets) as the encoder to obtain features (or ScatNet embeddings) and convolutional neural networks (CNNs) as the decoder to generate an image. The advantage of GSNs is that the parameters of ScatNets do not need to be learned, while the disadvantage of GSNs is that their ability to obtain representations of ScatNets is slightly weaker than that of CNNs. In addition, the dimensionality reduction method of principal component analysis (PCA) can easily lead to overfitting in the training of GSNs and, therefore, affect the quality of generated images in the testing process. To further improve the quality of generated images while keeping the advantages of GSNs, this study proposes generative fractional scattering networks (GFRSNs), which use more expressive fractional wavelet scattering networks (FrScatNets), instead of ScatNets as the encoder to obtain features (or FrScatNet embeddings) and use similar CNNs of GSNs as the decoder to generate an image. Additionally, this study develops a new dimensionality reduction method named feature-map fusion (FMF) instead of performing PCA to better retain the information of FrScatNets,; it also discusses the effect of image fusion on the quality of the generated image. The experimental results obtained on the CIFAR-10 and CelebA datasets show that the proposed GFRSNs can lead to better generated images than the original GSNs on testing datasets. The experimental results of the proposed GFRSNs with deep convolutional GAN (DCGAN), progressive GAN (PGAN), and CycleGAN are also given.

Vortex-induced vibrations of a long flexible circular cylinder

1993 ◽  
Vol 250 ◽  
pp. 481-508 ◽  
Author(s):  
D. Brika ◽  
A. Laneville
Keyword(s):  
Circular Cylinder ◽  
Flow Velocity ◽  
Vortex Shedding ◽  
Abrupt Change ◽  
Velocity Range ◽  
End Effects ◽  
Synchronization Region ◽  
Vortex Induced Vibrations ◽  
Set Up ◽  
Vortex Shedding Modes

In an experimental study of the vortex-induced oscillations of a long flexible circular cylinder, the observed stationary amplitudes describe an hysteresis loop partially different from earlier studies. Each branch of the loop is associated with a vortex shedding mode and, as a jump from one branch to the other occurs, the phase difference between the cylinder displacement and the vortex shedding undergoes an abrupt change. The critical flow velocities at which the jump occurs concur with the flow visualization observations of Williamson & Roshko (1988) on the vortex shedding modes near the fundamental synchronization region. Impulsive regimes, obtained at a given flow velocity with the cylinder initially at rest or pre-excited, and progressive regimes resulting from a variation of the flow velocity, are examined. The occurrence of bifurcations is detected for a flow velocity range in the case of the impulsive regimes. The coordinates of the bifurcations define a boundary between two vortex shedding modes, a boundary that verifies the critical curve obtained by Williamson & Roshko (1988). The experimental set-up of this study simulates half the wavelength of a vibrating cable, eliminates the end effects present in oscillating rigid cylinder set-up and has one of the lowest damping ratios reported for the study of this phenomenon.

scholarly journals Hemispherical–directional reflectance measurements of natural snow in the 0.9–1.45 μm spectral range: comparison with adding–doubling modelling

1998 ◽  
Vol 26 ◽  
pp. 59-63 ◽  
Author(s):  
Claude Sergent ◽  
Catherine Leroux ◽  
Evelyne Pougatch ◽  
Florence Guirado
Keyword(s):  
Temperature Gradient ◽  
Spectral Range ◽  
Experimental Results ◽  
Natural Snow ◽  
Reflectance Measurements ◽  
Directional Reflectance ◽  
Made In

The authors present the results of snow hemispherical–directional reflectance measurements on natural snow in the 0.9–1.45 μm spectral range. The measurements were made in a cold laboratory on snow collected in the field. Some of the samples have been subjected to controlled metamorphism in the laboratory before measurements were made. In the first part, the adding–doubling model, experimental assumptions and methodology are described. In the second part, experimental results are discussed and compared with theoretical values for different typical snow types and for different stages of snow evolution when subjected to temperature-gradient and wetness metamorphisms.

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